From esanders at erols.com Sat Apr 1 22:23:17 2000 From: esanders at erols.com (Nan and Sandy Sanders) Date: Thu Jul 3 13:41:42 2003 Subject: [Lf] WA2XTF-6 Message-ID: <01BF9C28.E61C4320.esanders@erols.com> Is back on the air. Found a broken ground wire. With fewer trees and no HF ant the current is about 1.9 amps. Sandy From fgentges at mindspring.com Sun Apr 2 05:30:13 2000 From: fgentges at mindspring.com (Frank Gentges K0BRA) Date: Thu Jul 3 13:41:42 2003 Subject: [Lf] WA2XTF-6 Message-ID: <052b01bf9c53$c2f94d40$0d1fa8c0@mercury> Sandy, Nice to hear it back on the air Frank -----Original Message----- From: Nan and Sandy Sanders To: 'LF@AMRAD.ORG' Date: Sunday, April 02, 2000 4:20 AM Subject: [Lf] WA2XTF-6 > > >Is back on the air. Found a broken ground wire. >With fewer trees and no HF ant the current is about 1.9 amps. > Sandy > >_______________________________________________ >lf mailing list >lf@amrad.org >http://www.amrad.org/mailman/listinfo/lf From akestelo at bellatlantic.net Sun Apr 2 12:08:42 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:42 2003 Subject: [Lf] ground planes ? Message-ID: <38E7627A.A782A19@bellatlantic.net> C Andersson wrote: > Hello LF group, > > I just want to share my last findings in the chase of "the missing dB's". > Yesterday I changed the antenna ground plane and added 10x6 m chicken wire around the antenna base plus 12 radials 20-25 m each. The chicken wire was solderable with a 300W soldering iron. > The feed impedance went down from 25 to 22 ohm. Not very much difference. > I have not used radials before, just a 8 m steel pipe + a various other ground connections in parallel. > Today's measurements however show a noticeable improvement of 1,6-2 dB (with the same antenna current). > Now, after all, the estimated ERP seems to correspond with measured values. > Interesting that the ground plane in some way improves the far field signal. > > (BTW, the cost/improvement factor is 400 SEK/dB + 5 working hours. (400SEK=46 USD)) > More details on my home page: http://home5.swipnet.se/~w-54761/fs.htm > > 73 > Christer > sm6pxj From akestelo at bellatlantic.net Sun Apr 2 21:06:22 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:42 2003 Subject: [Lf] Fast CW and big antennas Message-ID: <38E7E07E.1EBA8BD9@bellatlantic.net> The message below was posted by Steve Olney VK2ZTO on the RSGB reflector after a few somewhat acrimonious exchanges about "the bigger the antenna the better", and "those who don't have a good installation don't stand a chance", etc. (my summarizing of the exchange). Andre' N4ICK ********************************************* Steve Olney wrote: > G'day All, > > Once again, thanks to all that have replied directly. I'm sorry but I > can't reply to you all directly because of time restrictions. > > I must admit to be a little stirred up as it has become apparent from some > of the direct contacts to me that there are a significant number of > potential operators out there who are intimidated by the disparaging remarks > about modest installations to such an extent that they are discouraged from > entering the LF area of operation. > > Be reassured that there is a silent majority out there that will encourage > you no matter how small your installation is. The LF bands are NOT DXCC > bands or an arena for seeing who has the biggest this or that - it is, in > most countries, allocated as an EXPERIMENTAL band. That is why you can use > modes on LF which are not allowed in some countries on the HF bands (so I am > told). > > As for the assertion about relative costs for masts and transceivers. I > obviously am not in the same monetary class as those who would say that a > tower costing over ?2000 (over $5300 Aus) is an option. I do have a modern > transceiver which cost me nearly $3000 Aus but I saved for a long time (a > long time and much talking and justification with the XYL) for this, but it > gives me access to all bands to 70cm (including LF receive). > > Another contribution carries the implication that those who are keen to > engage in DSP should remember that not everyone has a PC. Well, over here > a PC capable of running Spectrogram (and other things - logging, antenna > analysis, etc) will cost you less than $500 - one tenth the cost of the > suggested tower from the other contribution. > > So to those that are thinking about getting on the air on LF - DON'T be put > off by the fear that your activity will viewed as not worth the bother. > The reason we have been granted the privilege of using these LF frequencies > is for experimentation (nowhere in the submissions for access to LF to the > relevant regulatory bodies will you find the purpose as being for DXCC, > biggest antennas or CW skills - but you will find the words experimentation > and investigation) and so if you want to experiment with a 6m pole and are > thrilled to make it over a 30km path - go do it!! If you do something > different from the accepted 'norm' then it could be argued that you have > made more of a contribution above what can be just copied from commercial > installations. If we just strive to mimic commercial installations what is > the point? How can we argue with our regulatory authorities that we are > worthy of access to LF if they see that we are just re-inventing the wheel? > > Finally, to those of you that emailed me with indications of being > discouraged because of the modesty of their installations, I can re-assure > you that there IS a silent majority out there whose LF capabilities range > from the very modest to the top-most capability whose motivation is one of > the pure thrill of the challenge (whether 10km or 2000km) and are competing > with the physics, etc, not each other. > > So in summary, there are plenty of us who just want to have a free exchange > of ideas while just a few want to mass debate :-) > > Regards Steve Olney > VK2ZTO > (P.S. I was going to add more letters here, eg., two Degrees and one > Diploma, but I didn't want to appear to be a wanker, and they are totally > irrelevant to Amateur activities anyway :-) From akestelo at bellatlantic.net Tue Apr 4 15:00:49 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:43 2003 Subject: [Lf] LF: S-meter readings...] Message-ID: <38EA2DD1.C27718AD@bellatlantic.net> vernall wrote: > Steve Olney wrote: > > > > G'day All, > > > > I have a question about something that has puzzled me for some time now. > > It concerns the procedure for giving signal reports. I understand the > > scale for readability - no problem. The problem I have is with the the > > signal strength part. The R part is a relative indication - relative to > > QRM/QRN etc, as I understand it. But what about the S part? > > > > In the case of a receiver which at the frequency and time of the received > > signal has an S-meter reading where the needle is just moved off the stop in > > the absence of a signal - an S-meter reading of 5 on a signal would seem to > > warrant a report of S5. > > > > However, the same receiver which might have a preamplifier added and at the > > time and ferquency of the received which has a no-signal reading of say 3. > > If that receiver now receives a signal which moves the S-meter up to a > > reading of 8 - what is the appropriate report for the signal? S8 or S(8-3) > > = S5? > > > > It seems to me that it is possible to have a high level of noise with a > > small signal which is barely readable but giving a S-meter reading of 8. > > > > Isn't closer to the truth to be giving S-points above the noise or am I > > missing the point? > > > > 73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40) > > Steve, > > Ideally one would use field strength to describe incoming signals, as > field strength is independent of the antenna and receiver. However, the > need for a calibrated antenna and receiver is a bit over the top for > amateur operators. The antenna has a changing "k factor" with > frequency. The field strength of the signal and noise could be > determined. As well, most field strength meters have linear meter > scales and no AGC applied to the RF or IF stages. > > A communications receiver usually has internal AGC, and an "S meter" > that is operated by AGC voltage. A receiver with AGC can not avoid > having a compressed S meter scale that is approximately logarithmic, and > is an advantage if a wide range of strengths is to be displayed on a > single meter scale, where accuracy is nominal. Ideally, the S meter > should read S9 for 50 microvolts applied to the RF input to the receiver > at the tuned frequency. Each S point below that is supposed to be -6 > dB per point. On most ham gear the S meter is gratuitously known by > some as a Guess Meter. > > Bob ZL2CA From akestelo at bellatlantic.net Tue Apr 4 15:08:00 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:43 2003 Subject: [Lf] more on S-meter readings...] Message-ID: <38EA2F80.309E1296@bellatlantic.net> "'Geri' Kinzel, DK8KW" wrote: > Hello Steve, > > when I learned for my license at the beginning of the 70ties, I still used > to learn the old system for S 1 to S 9 reports to be judged by ear. And > that of course depends very much on the background noise and several other > factors that are completely depending on the person giving the reprot. > > On LF I use a level-meter so I can read the signal strength directly in dBu > (0 dBu = 0.775 V). I calibrated this relative measurment using a one-meter > diameter loop so that I sould be able to determine strength in dB > microVolt/m within +/- 1 dB (still I am missing a couple of dB and don't > know exactly why ...). As a reference I use the (constant) signal level of > DCF39, so evem with a pre-amplifier or a different antenna I try to give > "absolute" dBu-reports for comparison purposes. But off course, if that > band is quit I can hear a station quite loed and would give it a S7 or 8 > report, when the band is noisy I can barely hear a station that is 20 dB > stronger, so just by ear I would give an S3 or 4 report by ear. What I try > to do on LF is to give a subjective RST report plus the dBu value. Also on > my homepage I list the dBu values, so at least everybody can judge how > strong his signal is relative to the other stations. So I believe what you > call S-units above noise comes close to the old S 1 to S 9 scale given by > ear and reflects more the audible quality of the system than the absolute > S-value. > > Best 73 > > Geri, DK8KW (W1KW) > http://www.qru.de From akestelo at bellatlantic.net Tue Apr 4 19:26:22 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:43 2003 Subject: [Lf] [Fwd: LF: Re: S-meter readings...] Message-ID: <38EA6C0E.9251B6D1@bellatlantic.net> Steve Olney wrote: > G'day Bob, Geri and others, > > OK thanks. I have a clearer picture now. Doing a napkin analysis and > taking into account the logarithmic nature of the S-meter readings, it seems > that, for example, if you have, say, S5 noise alone and then an S5 signal, > then the S-meter reads somewhere btween S5 and S6 - closer to S5. > Therefore an S5 report would be warranted as being pretty close. The > problem seems to be when you have, say, S5 noise and, say, an S2 signal. > The S-meter still reads S5. Giving an S5 report would seem to be suspect > under those circumstances. > > It always was on my mind when attempting to give RSTs that the readability > part is the only one where I feel that I am giving a true assessment (except > of course when the signal is way above the noise). Now I can see that as > long as there is a difference of 1 S-point between noise only and > noise+signal then the S reading is reasonable (although in guess-units as > Bob has pointed out). > > Thanks > > 73 Steve VK2ZTO From akestelo at bellatlantic.net Tue Apr 4 19:37:55 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:43 2003 Subject: [Lf] Re: re-inventing References: <38E8CAB4.47F7F568@netscapeonline.co.uk> <38E90FC3.38DF@xtra.co.nz> Message-ID: <38EA6EC3.F690A211@bellatlantic.net> > g3kev wrote: > > > > LF techniques covering every aspect have been documented over the years > > and while some purport to be inventing new methods they are really > > copying what has gone before. The broadcast industry has covered it in > > great depth and the various Government Agencies have also perfected the > > two way communications aspect especially narrow band methods. It seems > > the majority interested in LF do not realise this and think they are a > > first. > In fact, various government agencies (European Broadcasting services, US Navy, etc.) have indeed been involved in LF transmissions for many years. We should keep in mind, however, that those entities are above all interested in _reliable_ coverage and hence, tend to use as large a hammer as they can possibly find to drive down that nail, i.e., Radio Luxemburg and France Inter=2 megawatts, and see also our AMRAD website (http://www.amrad.org/projects/lf) for details and photographs of the now defunct NSS US Navy site at Annapolis,Maryland. We, amateur radio operators, are not necessarily interested in 24 hours/day coverage, and a QSO from time to time can be very satisfying. Hence, ground wave is not necessarily the only way to go, and once we start using skywave and QRSS, I am fairly sure that the above mentioned Government Agencies have little experience in those domains, mainly, again, because of unreliability or low throughput. But surely, that may be, for some of us, where the fun lies ? Finally, the ARRL Handbook has been printing since the 1920's a statement to the effect that "(The Radio) Amateur is Gentlemanly". I, for one, would not like to see this LF Forum, populated by a bunch of old friends, becoming a place where what sometimes sounds to me like ex cathedra statements are made and barbs exchanged. 73 Andre' N4ICK From fgentges at mindspring.com Fri Apr 7 03:07:31 2000 From: fgentges at mindspring.com (Frank Gentges K0BRA) Date: Thu Jul 3 13:41:43 2003 Subject: [Lf] Solar Storm Message-ID: <08de01bfa02d$a7d21a00$0d1fa8c0@mercury> It looks like we are having a real duzy of a solar storm. I may last for several days. Keep alert for LF changes due to this. Frank Gentges K0BRA ex AK4R, W3FGL For the latest on LF See http://www.amrad.org/projects/lf From akestelo at bellatlantic.net Sat Apr 8 10:23:07 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:44 2003 Subject: [Lf] [Fwd: LF: TransAtlantic II, test notice - announcement] Message-ID: <38EF32BB.D0E3AD9@bellatlantic.net> Larry Kayser wrote: > Greetings All: > > This is a preliminary notice to all LF amateurs in Europe and Canadian > amateurs interested in LF activities that the radio regulatory authority in > Newfoundland, VO1, has issued me, VA3LK, an experimental permit to operate > in the proposed LF amateur band of 135.7 kHz to 137.8 kHz. The project is > to be known as TransAtlantic II with a major test effort over the North > Atlantic to occur from November 10, to November 27th 2000. The attempt will > be made from the East Coast of Newfoundland with, I hope, two receiving > teams and one transmitting team. Each team will be independent and will > seek the best receiving sites and the best transmitting sites available > along the VO1 coast for the test. > > This notice seeks to provide preliminary and planning information for our > peers in Europe of the goals for TransAtlantic II. European amateurs have > been operating regularly on the LF band for some years now. It is my hope > to have them make similar efforts to ours in the operation of portable LF > stations during the three weekends over a two-week period next fall. > > Secondly this notice seeks to attract participants in Canada who will > develop the LF receiving skills and see how far west of Newfoundland that > TransAtlantic II signals might be received during the trial period. The > development of a receiving team in the Halifax area in conjunction with > Jack, VE1ZZ who has an excellent location and antennas is an initial > critical need. > > Third this notice seeks participation of VO1 amateurs and others who might > assist this team in finding the best receiving and transmitting sites on the > east coast of Newfoundland that we might be able to use, or obtain > permission to use, during the fall period. We have to consider staying as > far as possible from the Loran-C stations at Cape Race and at Fox Harbour in > VO2. We must also provide as much signal discrimination as possible from a > high powered existing station on 137 kHz in the Halifax area. > > The fourth, and at the end of the day a most important goal, is to > demonstrate to the regulatory authority that Canadian amateurs have the > skill and competence to operate in the LF part of the spectrum, and to share > with the existing users of this spectrum without interference. It is > important that amateurs are assigned opportunities in this part of the > spectrum so that we might make some contributions to radio science with our > work on these frequencies. > > TransAtlantic II will transmit and receive regular CW, special slow speed CW > that is known in the LF community as QRS CW at about .4 WPM, that is point > four WPM. We will also be transmitting what is known as Coherent- BPSK, > C-BPSK using the work of Bill de Carle, VE2IQ who has been an active and > dedicated researcher in the LF region for many years. Bill is part of is > the LowFer community here in North America. He has heard the LowFer signal > TEXAS at his home north of Montreal. TransAtlantic II seeks to build on the > LowFer technology that has been demonstrated with excellent results over a > long distance at power levels far below that to be used in the 135.7 to > 137.8 kHz band. > > The TransAtlantic II project will be making a financial appeal to the > Canadian amateur community at a later date. > > TransAtlantic II is also seeking the participation of a few more team > members who are prepared to put in long hours of preparation and then three > plus weeks of time on the east coast of Newfoundland in November. If you > can cope with cold coffee or even no coffee and a wet and cold work > environment and have some CW and computer skills and a passion for long > Beverage antennas you probably have the basics to be a team member! The > actual operating hours will only be from about 2000 utc each day until about > 0700 utc, so one should expect to get some sleep each night. > > First we must hear/see signals from Europe then we need to have our signals > heard in Europe and then a two way QSO. Until this happens, and we expect > this to happen during the test, we should expect to possibly move sites > between evening test periods as needed to achieve the goals of TransAtlantic > II. > > There is precious little time left to develop computer DSP skills, such as > expert use of the software Spectrogram and Gram, the LF listening and > antenna fabrication skills. If you want to participate the time to start is > now on an urgent basis. An LF beacon in eastern Ontario will be on the air > shortly, a LowFer beacon is on the air in Southern Ontario as well. > > I am pleased to announce that Mitch Powell, VE3OT will focus on the > technology development for the receiver teams. Mitch has extensive LF > listening and computer skills and has been a member of the LowFer community > for some years now. Mitch and I have already both undertaken some portable > operations ? we have begun to understand the issues involved in bringing > TransAtlantic II to an operational status. > > What can you do? You can solicit your club for funds to support > TransAtlantic II. You can build and operate an LF receiving station and an > associated computer system to try and hear/see the LF signals in Ontario as > well as during TransAtlantic II with Europe next fall. You can become a > TransAtlantic II team member. You can learn about LF and become active in > the LF community. > > If you can help or need additional information contact myself, Larry at > kayser@sypatico.ca or Mitch at PowellM@claven.fanshawec.on.ca for additional > information. > > Work with BPSK requires a Sigma Delta demodulator, contact Bill de Carle at > bill@ietc.ca. Bill has kits available and the software is available on the > Internet. Bill has an article on this unit, it is in QST for January 1992, > page 23. > > We are off an running with a new challenge in LF. Firsts do not come often > in Amateur Radio, I have been lucky to be in a few of them, this one has > lots of room for many to achieve new Firsts in LF. > > Let?s Go. > > Larry > VA3LK From akestelo at bellatlantic.net Sat Apr 8 10:26:02 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:44 2003 Subject: [Lf] from Mike Dennison re US LF Message-ID: <38EF336A.2E83B199@bellatlantic.net> Mike Dennison wrote: > > An LF beacon in eastern Ontario will be on the > > air shortly, a LowFer beacon is on the air in Southern Ontario as well. > > > > Larry (and Andre as well), > > In order for DX beacons to be REALLY useful, ie identifiable on > Spectrogram etc, they should ideally transmit continuously with > regular hand-speed callsigns for the audio boys, but also have > extremely slow CW imposed on it in very narrow FSK for weak > signal work. Something like 2 or 3Hz shift would be very visible on > a DSP program but inaudible to the listener. It may be that we > could have seen the USA beacons by now but it would have been > impossible to have made a positive identification in any case. > More work for you!! > > Well done on the test licence. > > Mike, G3XDV (IO91VT) > http://www.dennison.demon.co.uk/activity.htm From akestelo at bellatlantic.net Sat Apr 8 10:28:34 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:44 2003 Subject: [Lf] [Fwd: LF: QRS CW from Canada] Message-ID: <38EF3402.8880794F@bellatlantic.net> Larry Kayser wrote: > Mike: > > >In order for DX beacons to be REALLY useful, ie identifiable on > >Spectrogram etc, they should ideally transmit continuously with > >regular hand-speed callsigns for the audio boys, but also have > >extremely slow CW imposed on it in very narrow FSK for weak > >signal work. Something like 2 or 3Hz shift would be very visible on > >a DSP program but inaudible to the listener. It may be that we > >could have seen the USA beacons by now but it would have been > >impossible to have made a positive identification in any case. > >More work for you!! > > The Canadian beacon at this time is only for testing antennas, tuners, > tools, method and processes (RX and TX) and modulation methods to be used on > the TransAtlantic II effort. The modulation for the moment will be BPSK and > then some QRS CW and maybe, if there is a model for it, some FSK. > > After a QSO across the North Atlantic is a reality I will do other things > here from Westport for the duration of the license period in an attempt to > also get across North Atlantic from here. > > I hear your message, and I agree after we have done TransAtlantic II, then > all things are possible. For now the focus is not for general listening by > others, although I have nothing wrong with that, I would really like very > much to have a good 40 wpm QSO on LF, that would be a lot of fun and might > get some of my FOC friends interested hi. > > Please try and accept my single focus, TransAtlantic II is the only interest > here until it is done, or I am forced to admit failure. > > >Well done on the test licence. > > Thank you. > > Larry > VA3LK From akestelo at bellatlantic.net Sat Apr 8 10:39:17 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:44 2003 Subject: [Lf] Another use for CDs... Message-ID: <38EF3685.74C02EBB@bellatlantic.net> If you don't know what to do with all these AOL CDs you keep getting in the mail, go visit: http://www.netcomuk.co.uk/~wwl/cdzap.html Andre' N4ICK -------------- next part -------------- An HTML attachment was scrubbed... URL: http://atanasoff.rf.org/pipermail/lf/attachments/20000408/dd8ef4f7/attachment.html From akestelo at bellatlantic.net Mon Apr 10 08:10:02 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:45 2003 Subject: [Lf] [Fwd: LF: RE: TransAtlantic II] Message-ID: <38F1B68A.C2C0AD88@bellatlantic.net> Talbot Andrew wrote: > It would be unfortunate to limit ourselves to just use of these two > relatively simple pieces of DSP software which at the end of the day are > really just narrowband power detectors in not that narrow a bandwidth. > Remember, the very first long distance QSO on 73kHz between myself and > G3PLX was made in 0.04 Hz bandwidth using something like 300uW ERP with > plenty of signal in hand - whereas the likes of Spectrogram can only get > down to around 1.3 Hz BW. The same bandwidth can be achieved with a > filter made from 5 watch crystals at 32 kHz - I've done it. . > > I feel there is a lot more to be gained by coherent integration > techniques. Use of the VE2IQ software and other slow BPSK modes goes > some way towards this, but all suffer badly from the need for clock > recovery and tracking. The need to get initial timing information > throws away much of the usefulness of this mode. > The ultimate solution is to use GPS timing. I know quite a number of > operators in the US are now using GPS locked frequency and time sources, > and they are begining to make an appearance here. Having the > transition points of the bit intervals known precisely to the > microsecond (if the path length is known) leaves the signal recovery > task to be merely an integration over whatever time is needed for the > bandwidth with no lockup or preamble phase. > > TAPR have a range of GPS and frequency locking projects / kits. Who in > the US Lowfer community have the DSP hardware, even if not the > programming skills, to experiment with these techniques. Ideally, if a > Motorola DSP 56002EVM module, GPS receiver and carrier frequency known > accurately to milli Hz are availble software can be shared and > experiments made with known equipment capabilities. > > Some people are going to spend lots of time/money/effort on antennas and > PAs, why not put a similar effort into signal processing as well. So > what if it takes 10 hours to send a message, at least it will have been > sent from a station that does not have a farm on which to erect huge > antennas. > > Andy G4JNT > > >From VA3LK > > >There is precious little time left to develop computer DSP skills, such > as > >expert use of the software Spectrogram and Gram, .........- we have > begun to understand the issues >involved in bringing TransAtlantic II to > an operational status. > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From akestelo at bellatlantic.net Mon Apr 10 19:21:28 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:45 2003 Subject: [Lf] [Fwd: LF: Re.L.F. Antennas.] Message-ID: <38F253E7.FE2ED393@bellatlantic.net> LAWRENCE MAYHEAD wrote: > Hi All,When I first set up my 136 station I put up a Marconi "T" > vertical ant. 15M high 30M long.The best ant. current I could get from > my 400 watt amplifier was 1.8 amps.The measured ground /coil/copper > loss was 125 ohm! Over the past 6 months I have tried to improve this, > I have increased the top to 3 wires,increased the grounding from 2x4 > foot rods plus house wiring/water etc to 10x 4 foot rods, 20 radials > each about 50 feet long plus one radial 150 feet long ending up at an > earth rod in sea water! I also re-made the loading coil with thicker > wire.The total result of all this effort was 2 Amps !!! Not very > encouraging.This weekend I decided to start again.I replaced the "T" > with an inv.L using the same support (tree) at one end but 60M long to > another tree.SO I now have less wire in the air 60M instead of 3x 30M > but stretched out.The loading inductance has not changed so the > capacitance is the same. BUT the ant current is now 3 Amps!Does this > mean that the antenna wire needs to have a longer "footprint " on the > ground?,presumably the current density is less than under the 3 wire > top,but the new ant stretches beyond my radial system,and it is still > much better!.Does this also explain the reported good performance of > so called "long wire" antennas on this band?Food for thought.I am > hoping toimprove things further but I dont have room to extend the top > wire in a straight line,perhaps I will try a crooked L Hi. Checks with > Eznec indicate a R.Res of about .06 ohms for the "T " and .0675 for > the "L" so with the increased current I hope to have improved my > signal by at least 3db.73s Laurie. From akestelo at bellatlantic.net Mon Apr 10 23:17:23 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:45 2003 Subject: [Lf] RE: TransAtlantic II] Message-ID: <38F28B33.43E4FC73@bellatlantic.net> Larry Kayser wrote: > Andrew: > > Thank you for your thoughtful memo! We are in violent agreement. This said > I must bring several points to your attention. > > >It would be unfortunate to limit ourselves to just use of these two > >relatively simple pieces of DSP software which at the end of the day are > >really just narrowband power detectors in not that narrow a bandwidth. > > The piece from my announcement that mentions these two pieces of software > was for domestic Canadian consumption. I am dealing with many amateurs here > who have no exposure or experience with LF and specifically they have no > experience with LF and using either of the mentioned software packages. > > >I feel there is a lot more to be gained by coherent integration > >techniques. > > Yes, certainly, the work today needs to be rethought and redone enough to > make optimum of very fine frequency control and specific benefit from the > knowledge of time to a high degree of accuracy. I have been emailing with > Bill, VE2IQ on this subject seeking to find out if he feels it is time to > move to the next level. Our discussions are very preliminary at this point. > > >Use of the VE2IQ software and other slow BPSK modes goes > >some way towards this, but all suffer badly from the need for clock > >recovery and tracking. The need to get initial timing information > >throws away much of the usefulness of this mode. > > Well, it is not now optimum in terms of what can be done today, but we not > only need to see what can be done today but what the "reach" might be that > would give us a real push forward. > > >The ultimate solution is to use GPS timing. I know quite a number of > >operators in the US are now using GPS locked frequency and time sources, > >and they are begining to make an appearance here. > > Well I am sitting here with an old HP 5248L frequency counter with the guts > slowing coming out and the Oscillator awaiting the arrival of one of Brooks > Shera's boards to let my OEM GPS receiver stabilize the HP Oscillator to a > few parts in 10 to the -11th or so. > > >Having the > >transition points of the bit intervals known precisely to the > >microsecond (if the path length is known) leaves the signal recovery > >task to be merely an integration over whatever time is needed for the > >bandwidth with no lockup or preamble phase. > > Certainly. I understand the need, I do not have all the skills to pull it > off alone. But I can promise you that my transmitter here will meet all > such requirements. I have moved a Sulzer Labs high stability frequency > standard into my remote HF radio site, from which I will transmit LF signals > in Westport, and it will hold to a couple of parts in 10 to the -10th as it > is without further help. > > >TAPR have a range of GPS and frequency locking projects / kits. Who in > >the US Lowfer community have the DSP hardware, even if not the > >programming skills, to experiment with these techniques. Ideally, if a > >Motorola DSP 56002EVM module, GPS receiver and carrier frequency known > >accurately to milli Hz are availble software can be shared and > >experiments made with known equipment capabilities. > > Take this as offered, I am in an astonishingly high level of agreement with > you. My side here is ready, the basics are in place here to develop a > working system to a new level of accuracy. TAPR, as of a moment ago, do not > seem to have completed the work with the TAC2 to stabilize an oscillator. > Brooks Shera's work is available now and I am just waiting for him to let me > know the final price for the pieces and then he will ship be the bits I need > here. Please take a look at Brooks's site > http://www.rt66.com/~shera/index_fs.htm > I hope this will be useful to you. > > >Some people are going to spend lots of time/money/effort on antennas and > >PAs, why not put a similar effort into signal processing as well. So > >what if it takes 10 hours to send a message, at least it will have been > >sent from a station that does not have a farm on which to erect huge > >antennas. > > Andy, if we co-ordinated this announcement and your response we could not be > in a stronger level of agreement. > > Lets identify one thing. The TransAtlantic II effort this coming fall will > seek to do things with what we have now. We have no time to do more (in my > opinion), it is pushing us hard to get ready for November. I drove 150 > miles round trip today to interview a chap who used to tune up LF and > Broadcast Band (ours) antennas. I have a tad more skill in this area > tonight - and a pile of notes. > > When it comes to the next level, this is were I stand now. My friend Mitch, > VE3OT is working the issues with me. My station here is already taking > shape for the next level, I want to be part of this activity very much as it > is what attracted me to the LF scene in the first place. I have written > previously to David, G0MRF and to Dave, G3YXM about the use of AD9832, > AD9835, and AD9850 DDS devices so we could have milliHz control of the DDS. > David was kind enough to help me solve the exciter problem with one of his > boards so the situation for November is settled. Just this morning I have > had an offer from the US to get some boards that will fit the AD9835 device. > We are trying to see if we can fabricate a board here that will work with > the device. I have never worked with these thumb nail sized devices, but we > are going to keep going till we have RX's and TX's that are slaved to GPS > and we will have them here by this winter when we get back from VO1. > > For a start, until we have something better, I will start with Bill, VE2IQ's > work. His system has let him hear the TEXAS LowFer beacon at his home north > of Montreal. His GRAB capability is working here now. In the next few days > we will start to test this system over some 300 mile path. If there is a > way to go further, I want to be part of it and will do my best to be ready > when anyone else is ready. > > My last comment. On February 11th we missed a chance to probably bridge the > North Atlantic from here to the UK. I am not able to be here in the shack > during all hours of darkness but I sure would like to work you, computer to > computer, the next time we have a repeat of February 11th. I have a great > huge fire bell here in the basement that I would really like to hook up to a > computer that would go off when your signal is detected over here. Lets do > it..... > > Larry > VA3LK > > I am also sending a copy of this email to Mitch Powell and Bill de Carle, > please include them in any reply From akestelo at bellatlantic.net Wed Apr 12 09:20:31 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:46 2003 Subject: [Lf] [Fwd: LF: Re: TransAtlantic II, test notice - announcement] Message-ID: <38F46A0F.9831613@bellatlantic.net> Dave Sergeant wrote: > >From Dave G3YMC > > I wish Larry and the VE team all the best for their forthcoming > transatlantic tests - the choice of a period in November is excellent, and > if there is a chance then (and December) is the optimum time. > > There has been discussion here on the use of sophisticated coherent > reception techniques to achieve this aim. These may well be necessary, and > it is going to be no mean task. However who knows what will happen next > November. With the strength of CFH (and DCF39 in VE) some nights in the past > season my feeling is that it may not be as hard as we think. In the event > that a 2-way QSO is made using conventional CW and with antennas more in > keeping with a normal amateur station I think it would be fair to give > credit to that QSO, with a certificate or whatever, even though the first > QSO qualifiying for the Challenge may indeed be with specialist techniques. > > I think it would have given Peter Bobek a very special thrill if his aims > were met by a normal amateur using normal CW and an average station. It may > prove difficult (and it is certainly not possible with my existing set up!) > but it should not be considered impossible. Remember that at one time > transatlantic QSOs on Top Band were the rarity, whereas today they are > commonplace. > > 73s Dave > dsergeant@iee.org > http://ourworld.compuserve.com/homepages/sergeantd From akestelo at bellatlantic.net Wed Apr 12 10:18:51 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:46 2003 Subject: [Lf] Coil winding conundrum Message-ID: <38F477BA.44C6988F@bellatlantic.net> Talbot Andrew wrote: > Moving from LF to MF for a bit, here's a problem for the topband > operators and loading coil winders. > > At the weekend I made a loading coil to resonate the LF Tee antenna on > topband. 34uH was needed and the only suitable former to hand was 40mm > plastic drain pipe - the white type with no significant RF loss. > > First off I used 27 turns close wound of 1mm enamelled wire (which was > all that I had of that wire), and completed the coil with 20 turns of > 0.7mm diameter tinned copper with turns wide spaced at 3mm to allow > tapping points. > > This worked fine but I noticed the coil got a bit warm with 100 Watts > and decided I needed a higher Q.... > > So, I made some Litz wire by twisting 20 strands of 0.25 mm diameter > enamelled, which gives a copper X-sectional area a bit more than 1mm > diameter equivalent. Overall Litz wire diameter about 1.8mm. > 40 turns of this, close wound with a few taps gave near enough the same > inductance value for a winding length of 72mm > > Q was measured by connecting a 680pF cap in parallel, exciting the > circuit with a one turn coupling coil driven from a synth, very loosely > coupled and monitoring voltage across the coil with a x10 scope probe. > Peak response frequency was noted and then the points either side where > the response fell to -3dB (0.707) to get the bandwidth. Then Qu = CF / > BW > > Now for the interesting bit. When it came to measure the unloaded Q of > each coil, the original one was a fair bit higher at Qu = 140, compared > with the Litz wound coil with Qu = 95. Both coils were the same > diameter, same inductance, and roughly the same length in total. So > why was the one made of plain wire better ? Self capacitance ? Q > was only measured at 1 MHz, perhaps I should try measuring gain at a > lower frequency. > > Puzzled and curious.................. > > One interesting aside to come out though. Rayners formula for > inductance predicted the values of each coil to better than 10% and > bears out observations I've made over the years - such a simple > formula for wound inductors is too good to be true, working over a range > in excess of 1000000 : 1 > > L(uh) = (D.N) ^ 2 / (460.D + 1020 * length) D = mean > diameter, mm N = turns > > Andy G4JNT > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From akestelo at bellatlantic.net Wed Apr 12 15:54:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:46 2003 Subject: [Lf] lively exchange ... Message-ID: <38F4C67B.7DDE8083@bellatlantic.net> Tom Boucher wrote: > In message <38F422C1.A543FFD1@netscapeonline.co.uk>, g3kev > writes > >Square wave generators/dividers and class D/E amplifiers are fine for > >small antennas and low erp but NOT SUITABLE for larger antennas and high > >power. An abundance of LPF and BP filters might help to clean up the > >signal. > > Absolute rubbish! > > 73, Tom G3OLB > From akestelo at bellatlantic.net Wed Apr 12 15:57:00 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:47 2003 Subject: [Lf] LF: Coil winding conundrum] Message-ID: <38F4C6FB.8DAA2F34@bellatlantic.net> "Soegiono, Gamal" wrote: > Hello Andy G4JNT > > G4JNT> Both coils were the same diameter, same inductance, and roughly > G4JNT> the same length in total. So why was the one made of plain > G4JNT> wire better ? Self capacitance ? > > No. Unless the "capacity" exhibits significant dielectric losses, > great self capacitance does not harm in lieu of Q. > > What you probably have missed is to keep distance between > individual turns of the coil's winding. The effect of closely > winded turns is named proximitty effect. Current in one turn > tends to displace the current in the adjacent turn and vice versa. > > At "high" frequency AC we know the skin effect. That is, current > flow concentates on the perifery (surface) of a relatively large wire > diameter, rather than to evenly cover the total X-section > of the wire as it does for DC. > > If more than one wires are arranged to lay one beside the other, > the proximitty effect adds on in reducing the effecitve X-section > by displacing current flow even more as the skin-effect alone already > does. > > When constructing loop antenna windings, I try to keep a clearance > of at least 2 times the wire diameter in between individual turns and > always get optimum Q. For solenoid type of coils I recommend a minimum > of 1 wire's diameter of clearance. > > As the self-made Litz wire has a greater outer diameter, it's > relative close proximitty to the next turn reduces Q much more > than in the case of the solid wire. > > I recommend you build a third coil similar to the first one, where > you keep a clearance, equivalent of one/two wire diameters. > Try to keep the same aspect (coil former diameter to winding length) > as in coil 1. Would be interesting to know the actual difference in Q then. > > best 73 de Gamal > From DK8KW at compuserve.com Thu Apr 13 06:49:58 2000 From: DK8KW at compuserve.com (Holger 'Geri', DK8KW) Date: Thu Jul 3 13:41:47 2003 Subject: [Lf] Transatlantic, Signal Strength, DCF39, etc. Message-ID: <200004130550_MC2-A10A-3483@compuserve.com> Dear LF-band enthusiasts, as Gamal wrote in an earlier message, he and myself took a nice ride to the Burg transmitter facility, took some pictures and a field strength profile from the location back to my home QTH, approximately 120 km away. I hope to be able to post the profile, some further information as well as photographs of the antenna structure. As DCF39 is one of the few LF signals that has been heard on the other side of the atlantic, it might be interesting for further field strength calculations to know the ERP. With our measurements with an untuned 1m-diameter loop and a calibrated level meter (MV61, as my Siemens D2108 gave up its work) we came to the result, that the 50 kW DCF39 signal on 138.830 kHz mark frequency is being transmitted from a 325m high antenna. The actual ERP we came up with (matching the appropriate CCIR-curves with a very good correlation) is 40 kW ERP. So for all you guys in Canada or the U.S. that are able to hear DCF39, you might consider this ERP in relation to an amateur signal of only 1 W ERP (but maybe 1000 km closer to you location if it is a UK or Irish station). But that brings me to another measurement that I have made and something that was mentioned in a previous message written by Mike, G3XDV (IO91VT) >Don't forget that the transmission was a full 1W ERP (from only >10W in!). Very few amateur stations are able to run that amount of >power even with hundreds of watts input. I believe that most of us over-estimate their ERP by far (and I include also those guys with 'real' antennas). I myself calculated from the antenna current and the height of my umbrella antenna (18m) an estimated ERP of 200 mW. With the above mentioned equipment I actually measured the ERP to be only 30 mW (!). Field strength measurements performed by Dick, PA0SE, Markus, DF6NM and myself also indicate, that probably only two or three stations within Europe actually reach the 1 Watt ERP line (considering all the difficulties of actually measuring ERP from a distance beyond near-field). G3WSC/p obviously is one of those stations and as I indicated earlier, their signal was exactly on my theoretical 1 Watt ERP line. I am still surprised that with my actual ERP being that low, my signal still can be considered an average signal and allowed me to cover distances of up to 1300m (one of the disadvantages of living in Central Europe is that there simply is no active LF station further away -- yet ...). Even more I am surprised that with an antenna by far less effective I was able to run my first Slow-CW QSOs over a distance of 402 km with ON7YD last year with an ERP of (theoretcically, based on my actual measurments and calculations) less than 0.1 mW (!!) ERP. This shows me, that, providing we select the appropriate technique, the detection of estonishing weak signals out of the noise is possible. The only other places I personally know working with similar techniques are military (submarine communcation), radio astronomers, NASA, and geophysical people (seismics and oilfield applications to transmit data wireless from the borehole bottom to surface) as well as our EME collegues! Geri, DK8KW (W1KW) P.S.: what I have heard (and read on the internet somewhere), NASA people used spectrogram-like software to look for signals of the missing MARS vehicle last year ... so much to the application of "amateur" techniques by the professionals and vice versa. From akestelo at bellatlantic.net Thu Apr 13 15:37:44 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:47 2003 Subject: [Lf] Re: TransAtlantic II] Message-ID: <38F613F8.49AC4365@bellatlantic.net> Peter Dodd wrote: > > From Dave G3YMC > > > I wish Larry and the VE team all the best for their forthcoming > > transatlantic tests - the choice of a period in November is excellent, and > > if there is a chance then (and December) is the optimum time. > > > I think it would have given Peter Bobek a very special thrill if his aims > > were met by a normal amateur using normal CW and an average station. > > I don't recall that DJ8WL had any hang-ups about using QRSS - in fact > all my QSOs with him used this mode > > Of the modes proposed for these Transatlantic tests the extremes are > 30 or 40WPM CW and slow CW that would take several hours. From > experiance gained in the last couple of weeks in crossband tests on > 72kHz/137kHz, mainly with I5TGC, I feel that the following notes may > be of some interest. > > Even in good conditions a signal radiated from 1W erp is going to be > very weak by the time it has travelled 3000km, even on a sea path. In > periods of exceptional conditions such a signal may be audible but a > much greater chance of success can be had by using QRSS. This can > illustrated by a 72/137kHz cross-band I had with OH9UFO. Reino was > using nomal CW on 137kHz. I was a comfortable 'O' on QRSS. I was > asked to try fast CW and Reino copied his report and gave me 329 - > then lost it. This QSO was very marginal and if it wasn't for the > inital QRSS contact it would not have happened. > > We have very little knowledge of the long distance propagation > mechanism of weak signals at LF. All we can say is (from observing > commercial stations) that they seem better in Winter at around > 0400UTC for this path. The greater the distance the shorter the > openings so digging the signal out of the noise using very long > integration times is impractical. > The openings for the I5TGC experiments lasted half an hour, which > gave plenty of time for QRSS with a dot length of 3 or 4 seconds. > > Exceptional conditions can occur any time so we should not confine > the tests to special expeditions. We should have a plan. > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Thu Apr 13 15:55:37 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:48 2003 Subject: [Lf] Re: 136k / 73k High power. References: <7b.2f14187.2627379d@aol.com> Message-ID: <38F61828.2DCEB464@bellatlantic.net> hello Dave, 100 watts ERP, ...wow! When can we expect to know: a) frequency ? b) times of transmissions? 73 Andre' N4ICK ************************** G0MRF@aol.com wrote: > Hi Andre' > We have just been given permission to run 100 Watts ERP this weekend. > Alert the troops. > Details to follow. Suggestions welcome. > We realise that this would not count for the transatlantic challenge due to > non amateur power and commercial antenna. > 73 > David From akestelo at bellatlantic.net Thu Apr 13 15:59:26 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:48 2003 Subject: [Lf] Key clicks and linears Message-ID: <38F6190E.C67B43C5@bellatlantic.net> howett@mail.globalnet.co.uk wrote: > Hi All, > > Thought I'd try a bit of calm consideration in the key click > debate,and thus offer the following discourse: > > Key clicks are broad-band radiation produced as a result of the rate > of rise and decay of the amplitude of the keyed carrier. The faster > the rise and fall, the closer to a square wave is the envelope and > the richer in harmonics is the resulting signal. Note that these are > not harmonics of the signal frequency, but of a very low frequency > related to the characteristics of the carrier's rise and fall. These > mix with the carrier frequency to produce a broad signal centred on > the carrier frequency. No amount of filtering of the clicky signal > can remove the clicks, although they are of course attenuated at > frequencies removed from the carrier frequency by any selectivity > between their source and the antenna. > > The only way to prevent key clicks is to ensure that the rise and > fall times of the keyed carrier are long enough to avoid significant > harmonic generation.( Although too long rise and falls results in a > "mushy" sounding signal that can be difficult to copy). > > > Once a clean keyed signal has been produced, it has to be preserved > through the remainder of the transmitter amplifier chain. A truly > linear amplifier will reproduce the input signal perfectly, and the > output will be click free. But note that maintaining linearity when > dealing with a switched carrier places severe demands on the > amplifier - a favourite problem is with sagging supply voltages.A > 'scope may show things a meter can't! > > Any form of "switching" mode amplifier (ie class C and above)is > inherently non - linear and relies on the flywheel effect of its > tuned circuits to produce a sine wave, and to filter harmonics > from its output. This results in the steepening of the rise time of > the signal, and can cause the appearance of clicks on a signal that > was clean when generated. The effect can be counteracted by > increasing the rise time of the keyed signal to allow for subsequent > "sharpening" of the waveform during amplification. > > In conclusion, any form of amplifier or exciter can be a satisfactory > solution provided it is designed and operated to be so - and this > includes digital techniques,provided that the appropriate filtering > and signal conditioning is used. > > Thats all from my soap-box for now, thanks to all those carrying out > any work on the VLF bands, whether wheel reinventing or not - what > matters to me is that there will be people to talk to when I > eventually get my transmitter (clicky or otherwise) on the air! > > 73 de Paul G4MD From DK8KW at compuserve.com Thu Apr 13 16:14:24 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:48 2003 Subject: [Lf] LF: Transatlantic, Signal Strength, DCF39, etc. Message-ID: <200004131514_MC2-A11D-595A@compuserve.com> Dear friends, following my previous mail, I just updated my longwave homepage with more information on DCF39, including pictures, the field strength profile and the ERP measurement (40 kW ERP) Gamal and I took last week, as well as information on how I measured the ERP of my own station in comparison (only 30 mW !). Just go to http://www.qru.de and follow the "What's New?"-link. Best 73 Geri, DK8KW (W1KW) From akestelo at bellatlantic.net Thu Apr 13 16:20:25 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:48 2003 Subject: [Lf] litz vs. regular wire... Message-ID: <38F61DF8.43FC04CF@bellatlantic.net> Peter Dodd wrote: > > G4JNT> Both coils were the same diameter, same inductance, and roughly > > the same length in total. So why was the one made of plain > > wire better ? Self capacitance ? > > Gamal> No. Unless the "capacity" exhibits significant dielectric losses, > > great self capacitance does not harm in lieu of Q. > > What you probably have missed is to keep distance between > > individual turns of the coil's winding. The effect of closely > > winded turns is named proximitty effect. Current in one turn > > tends to displace the current in the adjacent turn and vice versa. > > > When constructing loop antenna windings, I try to keep a clearance > > of at least 2 times the wire diameter in between individual turns and > > always get optimum Q. For solenoid type of coils I recommend a minimum > > of 1 wire's diameter of clearance. > > As the self-made Litz wire has a greater outer diameter, it's > > relative close proximitty to the next turn reduces Q much more > > than in the case of the solid wire. > > I use a 400uH commercial variometer in series with my main loading > coil for tuning. This single layer solenoid coil is wound with Litz > wire and the spacing is about 1.5 wire diameter. > > The main loading coil is wound on plastic fencing material formed > into a cylinder. It was not possible to maintain a one wire spacing > so I compromised and wound the coil in 'bunches' of 10 windings. > > A lot of effort goes into the design of professional LF coil design, > to reduce adjacent wire proximity while retaining a managable small > size as can be seen in the design of the Decca transmitter coil > formers (hopefully, more will be reveilled when I can figure it out). > Fairly complex coil design articles appeared in early publications, > which described basket and honeycomb winding patterns. > I will try to get some of this into the next edition of the LF Book - > the main problem is the illustrations! > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Thu Apr 13 16:26:23 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:49 2003 Subject: [Lf] more about Litz wire Message-ID: <38F61F5F.92B7692B@bellatlantic.net> Talbot Andrew wrote: > Well, Gamal and Paul between them hit on the solution. It definitely > appears to be proximity effect causing extra losses for the Litz wound > coil. I re-measured both at 80kHz and the Litz one came out > significantly better at 42 as opposed to 30 for the single layer one. > The losses caused by proximity effect obviously dominating the tiny > improvement from not very efficient Litz winding with each strand still > 4 - 5 skin depths in diameter. > Dielectric loses were insignificant, the former material barely got warm > in a Microwave oven. > > G4MD : > >Would not increasing the Q > >lead to higher circulating currents at resonance, thus greater > >heating? Unless of course the effective x-sectional area of the > >conductor was increased in square-law relationship to the increase in > >current! > > Q is only the relationship between loss resistance and reactance. A > higher Q means lower series R and must mean lower loss. It all falls > out in the maths :-( > > ZL2CA: > >You did not report in your findings if the Litz wire coil ran cooler > >than the single wire coil, but I am presuming it did. > > I did not even bother loading up, it was obvious from the Q measurement > it would dissipate more so not worth trying. > > -------- > I wound a new coil as Gamal suggested. Using 68mm diameter drain pipe > (I bought a 2m length for the grand sum of ?2-60 - anyone want some coil > formers :-) 42 turns of 0.8mm tinned wire spaced at 3mm over a length > of 130mm. Q now twice that for the original single layer coil at 250. > I couldn't use the spacing to conductor diameter ratio of 1.4 to 2.2 > that Peter suggested as it was difficult winding the bare wire onto the > smooth former with a spacing much less. > > It was very instructive comparing the measured loss resistance from Q > value with that calculated from conductor length, diameter and skin > depth. For both single layer coils the actual loss resistance was only > about twice that calculated. Considering what other loss mechanisms are > present, this result is very satisfyingly close. > > Now I suppose I'd better actually have a QSO on topband although I've > still got to measure the antenna properties on that band and compare > them with the values measured when it was first built for 73/137. > Anything to avoid going on air ! > > All the fun is in making things work rather than using them when they do > :-) > > Andy G4JNT > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From akestelo at bellatlantic.net Thu Apr 13 16:34:30 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:49 2003 Subject: [Lf] Noise measurements Message-ID: <38F62146.D4CDF6F6@bellatlantic.net> Very interesting study of noise. Well worth clicking on http://home.t-online.de/home/dk8kw/noise.htm 73 Andre' N4ICK From DK8KW at compuserve.com Fri Apr 14 01:16:01 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:49 2003 Subject: [Lf] Alert: G3WSC/p with 100 W ERP this weekend! Message-ID: <200004140016_MC2-A12F-C037@compuserve.com> Von: INTERNET:rsgb_lf_group@blacksheep.org, INTERNET:rsgb_lf_group@blacksheep.org An: "INTERNET:rsgb_lf_group@blacksheep.org", INTERNET:rsgb_lf_group@blacksheep.org Datum: 14.04.100 00:57 BE: LF: Puckeridge tests 14/15 th April - Proposed Schedules Dear LFer's The Notice of Licence Variation from the Radio Communiction Agency has just approved to operate up to100W ERP from the 325 ft Decca mast on both the 73Khz band (callsign G3GRO) and the 136Khz band (callsign G3WSC) over the weekend 14/15/16 April !! Herewith the proposed initial operating periods for the forthcoming weekend from the old Decca site :- From 16-00 UTC - 1700UTC 73Khz Band 1W ERP 17-00 UTC - 20-00 UTC 136Khz Band 1W ERP 20-00 UTC - 2100 UTC 73Khz Band 1W ERP 21-00 UTY - 2300UTC 136Khz Band 1W ERP After CQs we will indicate where we will be QRX , We also hope to be able to QSX HF bands Note # We may run some tests for limited periods at higher ERP reducing in steps from a maximum 100W ERP ( 1Kw RF to antenna) announcing the ERP at each level From 2300 -05-30 UTC 137.710 Khz Beacon mode -- sending alternate callsign G3WSC for 10 secs (about 5wpm) and then 10sec pause, then callsign again etc. ERP up to a maximum of 100W Later schedules for Saturday onwards will be posted on the reflector The operators involved at various times over the weekend will be - G3KAU, G3GRO, G0MRF,G3XDV, M0BMU , G3XTZ, G3YXM, G3YSX On site mobile phone no. 07790 242930 Contact station back home - Peter G3LDO Tel No: 01903 770 804 or E-mail NB. The key clicks reported by some stations at close range after the first setting -up tests have hopefully been addressed. 73, de G3GRO, G3KAU, G0MRF From DK8KW at compuserve.com Fri Apr 14 01:17:46 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:49 2003 Subject: [Lf] Re: LF: Transatlantic, Signal Strength, DCF39, etc. Message-ID: <200004140017_MC2-A12F-C043@compuserve.com> -------------Weitergeleitete Nachricht----------------- Von: INTERNET:rsgb_lf_group@blacksheep.org, INTERNET:rsgb_lf_group@blacksheep.org An: , INTERNET:rsgb_lf_group@blacksheep.org Datum: 14.04.100 02:04 BE: Re: LF: Transatlantic, Signal Strength, DCF39, etc. In a message dated 4/13/00 8:23:48 PM GMT Daylight Time, DK8KW@compuserve.com writes: << following my previous mail, I just updated my longwave homepage with more information on DCF39, including pictures, the field strength profile and the ERP measurement (40 kW ERP) Gamal and I took last week >> Is this reasonable? : If DCF39 is 40kW ERP and G3WSC is 100 W ERP..... Then that's a ratio of 400 : 1 or 26dB. Which makes G3WSC apx 4 S-Points below DCF39 on the other side of the Atlantic. ( I've allowed .333 S-Points for the shorter distance) Good Luck for Fri / Sat. and thanks for the field strength measurements / ERP estimates Geri and Gamal 73 David 'MRF ----------------------- Internet Header -------------------------------- Sender: majordom@post.thorcom.com Received: from post.thorcom.com (post.thorcom.com [212.172.148.70]) by sphmgaad.compuserve.com (8.9.3/8.9.3/SUN-1.9) with ESMTP id UAA19993; Thu, 13 Apr 2000 20:03:46 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12ftY2-0006ps-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 14 Apr 2000 01:01:22 +0100 Received: from imo-d01.mx.aol.com ([205.188.157.33]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12ftY0-0006oT-00 for rsgb_lf_group@blacksheep.org; Fri, 14 Apr 2000 01:01:21 +0100 Received: from G0MRF@aol.com by imo-d01.mx.aol.com (mail_out_v26.6.) id l.ea.405e883 (3894) for ; Thu, 13 Apr 2000 20:00:34 -0400 (EDT) From: G0MRF@aol.com Message-ID: Date: Thu, 13 Apr 2000 20:00:33 EDT Subject: Re: LF: Transatlantic, Signal Strength, DCF39, etc. To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: AOL 5.0 for Windows sub 32 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: From akestelo at bellatlantic.net Fri Apr 14 09:11:45 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:49 2003 Subject: [Lf] LF: Puckeridge tests 14/15 th April - Proposed Schedules] Message-ID: <38F70B00.2E5D8458@bellatlantic.net> DEREK ATTER wrote: > Dear LFer's > > The Notice of Licence Variation from the Radio Communiction Agency has > just approved to operate up to100W ERP from the 325 ft Decca mast on both > the 73Khz band (callsign G3GRO) and the 136Khz band (callsign G3WSC) over > the weekend 14/15/16 April !! > > Herewith the proposed initial operating periods for the forthcoming weekend > from the old Decca site :- > > From 16-00 UTC - 1700UTC 73Khz Band 1W ERP > > 17-00 UTC - 20-00 UTC 136Khz Band 1W ERP > > 20-00 UTC - 2100 UTC 73Khz Band 1W ERP > > 21-00 UTY - 2300UTC 136Khz Band 1W ERP > > After CQs we will indicate where we will be QRX , We also hope to be > able to QSX HF bands > > Note # We may run some tests for limited periods at higher ERP > reducing in steps from a maximum 100W ERP ( 1Kw RF to > antenna) announcing the ERP at each level > > From 2300 -05-30 UTC 137.710 Khz Beacon mode -- sending > alternate callsign G3WSC for 10 secs > > (about 5wpm) and then 10sec pause, then callsign again etc. > > ERP up to a maximum of 100W > > Later schedules for Saturday onwards will be posted on the reflector > > The operators involved at various times over the weekend will be - > > G3KAU, G3GRO, G0MRF,G3XDV, M0BMU , G3XTZ, G3YXM, > G3YSX > > On site mobile phone no. 07790 242930 Contact station back home - Peter > G3LDO Tel No: 01903 770 804 or E-mail > > NB. The key clicks reported by some stations at close range after > the first setting -up tests have hopefully been addressed. > > 73, de G3GRO, G3KAU, G0MRF From akestelo at bellatlantic.net Fri Apr 14 09:15:58 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:50 2003 Subject: [Lf] LF: DSP Experimentation, Antenna book etc. Message-ID: <38F70BFD.590D69E1@bellatlantic.net> Talbot Andrew wrote: > If anyone wants to experiment with simple DSP techniques beyong just > plugging in Gram etc, or even wants to try some programming without > having to learn Windows API calls and how to use the soundcard, ICs for > the serial port interface described in RadCom a good few years ago are > still available. > > For those who don't remember the article, this was an 8 bit A/D > converter digitising audio at 10000 / 7142 / 2500 Hz and sending the > samples up the serial port to a PC. The idea being that this was a > simple way for users to develop their own DSP type software in standard > high level programming language without having to bother with the > digitising side of matters. PC software available with the module at > the time generated waterfalls and spectrum plots, although I have to > admit that for these functions alone, these days you are better off > using Gram and the Soundblaster. With slightly different PIC code for > the interface, and a change of crystal, it will also work at 7200 Hz > sampling instead of the overcomplicated sigma-delta interface specified > for the VE2IQ software > > One function also available with this module was a simple downconversion > from a 1000 Hz tone to zero frequency, the output consisting of Inphase > and Quadrature components allowing phase measurements and vectorscope > type programmes to be written easily. As far as I know, this function > is not yet freely available for the S/B (sits back and waits for howls > of refutation). > > A quick plug now - a commercial version of this interface with > additional slow speed data logging functions built in, is available from > HF Instruments - see their advert in the latest RadCom and web page > HF-INST.CO.UK. The data logging function could be useful, for instance, > for recording the AGC line over many hours while listening to a > propagation beacon in the same way that a chart recorder would be used. > > To Larry and Co. if you have a 56002EVM available I now have some > software for the PC that will let you sample a signal at 0.035 Hz (much > faster rates are also of course possible), and produce waterfalls this > wide looking in a bandwidth of 0.00012 Hz (yes, 120uHz). For QRSS > that would require a dot length of 4 - 7 hours and around 12 days for a > callsign. Rather silly but quite possible! > I produced an overnight Dopplergram plot of the DCF77 time transmission > and managed to clearly see some ionospheric spreading at night not > present during the daylight hours. There really are visible ionospheric > effects on 77 kHz signals but the picture is marred by the few mHz drift > due to the Codec crystal changing the sampling rate as the room cooled > in the night. If anyone wants a copy of this contact me directly on > G4JNT@ARRL.NET > > After reading all comments / discussions / arguments / heated debate > about antennas recently ........ > Just found a very good book on antenna design on a work colleague's > bookshelf. > > "The Handbook of Antenna Design" Vols 1 & 2 by A Rudge, K Milne et al. > ISBN 0-86341-052-9. > > Thought by many to be one of the best books on antennas there is. > After a serious bit of arm twisting I managed to borrow it from him for > a few days. There is a decent sized chapter (over 100 pages) on VLF / > LF antennas and another large chapter on HF ones. > More importantly it does not have pages upon pages of squiggly maths - > just simple equations that the average non-mathematician can actually > use and plenty of diagrams and graphs to just read off the results. > > And finally ........... > > To those who complained they have never heard me on LF. I don't, and > won't, operate normal speed CW. I hate the mode but will just about use > it under protest on 10 GHz where it works well for rainscatter (and we > keep to decent speeds with much repetition anyway). On LF I intend to > stay with the far more effective (in S/N terms even if not in > simplicity) PSK and other systems even if it means very few people to > work ! Morse might be cheap and simple, but that is it's only > advantage these days. CW may well be a skill, but not one I'm prepared > to practice at keeping up (Sits back and waits for even more flak !) > > Andy G4JNT > > -- From akestelo at bellatlantic.net Fri Apr 14 17:55:07 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:50 2003 Subject: [Lf] [Fwd: LF: Discussion of the Peter Bobek award, and TransAtlantic II] Message-ID: <38F785AA.B287CFA2@bellatlantic.net> Larry Kayser wrote: > Greetings All. > > Gentlemen: > > I would sincerely appreciate if discussions about the Peter Bobek award in > any terms of the activities of the TransAtlantic II project be avoided now > and until after TransAtlantic II results are known at the end of next > November. > > I am very sure that Peter Bobek was a person of honour, and some justly feel > that the award was conceived and now promoted as a recognition of a great > achievement in LF. > > The facts are, that the award requirements must and will have ZERO impact on > how TransAtlantic II will be undertaken from this side of the Atlantic. I > have only read the award requirements in a most cursory manner and will not > read them again until after we return from VO1 in November. I have nothing > against or for the award, but I do know my focus - have signals heard both > ways and if possible get a two way QSO across the North Atlantic in > November. > > The simple facts of the matter are, that what we have to do to get an LF QSO > in the amateur LF band across the North Atlantic the FIRST time will be many > dB in excess of what will be required to have the 200th or 2000th QSO across > the North Atlantic on LF. > > We can test the results achieved by TransAtlantic II, and wouldn't it be > wonderful if we could do it with 1W erp, after the test period is over. If > the award requirements have been met then well and good. If the award > requirements have not been meet this also is well and good. My personal > feelings are that I would really like to have a serious discussion later > this year about the qualification for the award, that would mean that some > signals were heard either way or a completed QSO was achieved over the North > Atlantic..... > > Summary, the award does not drive the project, the award is a byproduct of > the results of the project. > > Larry > VA3LK From akestelo at bellatlantic.net Fri Apr 14 18:12:54 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:51 2003 Subject: [Lf] LF: Decca mast and coils... Message-ID: <38F789D6.5F8D18D@bellatlantic.net> Walter Blanchard wrote: > There's a pic of the Decca mast the DMG are using this weekend > at: > http://www.blacksheep.org/lf/decmast.jpg > and a pic of the old Decca ATU coils at: > http://www.blacksheep.org/lf/coils.jpg > > There had to be five coils because Decca transmittted on five frequencies > simultaneously three times a minute. > Made the aerial current to go up to 60A!!!!! > > Walter G3JKV - the kid of the party - I'm only 69! -------------- next part -------------- An embedded message was scrubbed... From: Walter Blanchard Subject: LF: Decca mast Date: Fri, 14 Apr 2000 20:29:31 +0100 Size: 1805 Url: http://atanasoff.rf.org/pipermail/lf/attachments/20000414/9b716089/attachment.txt From akestelo at bellatlantic.net Fri Apr 14 18:14:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:51 2003 Subject: [Lf] Discussion, please, Coast location vs DCF39] Message-ID: <38F78A4C.FB3239CE@bellatlantic.net> "Holger 'Geri', DK8KW" wrote: > Larry, > > >A vigorous discussion on the path loss over land issues will be most > >appreciated. > >Larry > >VA3LK > > at least the pass loss over Germany seems not to be as serious as we > anticipated. If you have a look on my homepage (www.qru.de), you will see > that all theoretical calculations make the field strength curve bend > downwards after 80 or 100 km. What Gamal and me measured, showed a strict > logarithmic behaviour at least up to my door (120 km away from DCF39). So > there is hope for some dB ... > > But seriously: I think you saidpreviously that you was able to hear DCF39 > above the noise, so as G0MRF and ON7YD said in an earlier mail its only 26 > dB difference and that should hopefully do it (I can detect QRSS signals > approximately 15 to 20 dB below the weakest signal I just can detect by ear > ...). The difference between my signal and DCF39 is about 61 dB, that > sounds a little bit too difficult ... and I am sure it does not help that I > am 120 km closer to Canada compared to DCF39 ... so lets first try with the > Decca-Mast Gang! > > Best 73 > > Geri, DK8KW (W1KW) From DK8KW at compuserve.com Sat Apr 15 01:57:02 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:51 2003 Subject: [Lf] Field Strength G3WSC in DL Message-ID: <200004150057_MC2-A147-7F2A@compuserve.com> Hello YLs and OMs, I made some field strength measurements of the G3WSC operation as follows: Call ERP as Field Strenght said in QSO ============================================================= G3WSC/p 1 W ERP 19.1 dB microVolt/m G3WSC in QSO yesterday night 13 W ERP 24.1 dB microVolt/m G3WSC Beacon Saturday morning ? 34.1 dB microVolt/m at a distance of 697 km as comparison 7S6SAJ ? 41.6 dB microVolt/m at a distance of 737 km. (to compare with other signals on my homepage: add 108.1 dB to the dBu values shown in the table, I will update my table with dB microVolt values soon). The CCIR-propagation curves for ground-wave propagation roughly indicate a field strength of 45 dB microVolt/m for a 1 kW ERP signal at a distance of 700 km (depending on ground conductivity). As my measurments were just taken randomly, they include some variables such as varying propagation, day- and night difference, etc. and therefore are not completely consistent. However, the data at least give some indication about the radiated power. Keep on the work, its worth doing it! I will keep on observing and measuring, hopefully catch your signal on 73 kHz today, I am looking especially for my first 'normal CW' crossband QSO. What are your operarting frequencies and schedules for 73 kHz? Vy 73 Geri, DK8KW (W1KW) http://www.qru.de From DK8KW at compuserve.com Sat Apr 15 04:58:07 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:51 2003 Subject: [Lf] Slow CW Sensitivity Measurments Message-ID: <200004150358_MC2-A152-6777@compuserve.com> Hello friends, I made some laboratory tests this morning to get some indication about the ability to communicate with signals below noise level using Slow-CW. I used a calibrated frequency synthesizer (Adret 2230), an 0-120 dB attenuator in 1 dB steps (Schlumberger BMD500) and my Praecitronic MV61 Selective Level Meter. With a BNC t-connector I fed the normal band noise including loran lines on 137.500 kHz (+/- 50 Hz) to one side of the t-connector, and the output of the frequency synthesizer to the other side. With the attenuator I made sure that a 0 dBm (50 Ohm) signal with the synthesizer corresponds to a -80 dBu (75 Ohm) signal at the MV62 (plus/minus 1 dB). The band was quite this morning, with a background noise around -110 dBu (approx. S 4) and Loran lines clearly visible. Using the 100 Hz bandwidth of the MV62 and the cascaded 250 Hz/500 Hz CW filters of the IC-746 I checked the signal by ear as well as with the Spectrogram software with the normal parameters I use for "3-5 second-dot-length" Slow-CW (5.5k sample rate, 16bit mono, 16384 points FFT = 0.3 Hz resolution, 60 dB scale, 300 ms time scale, 10 x average) and obtained the following results: Injected Received Comment Signal Signal Strength Strength - 20 dBm - 100 dBu good audible CW signal (approx. S6) - 30 dBm - 110 dBu CW signal approx. equal to background noise (S4), just can be copied - 35 dBm - 115 dBu boundary for aural CW, signal just detectable by ear - 45 dBm - 125 dBu good "O" signal in Slow-CW, signal same level as Loran-lines - 50 dBm - 130 dBu still good readable Slow-CW signal "M" - 55 dBm - 135 dBu Slow-CW just detectable "T" - 60 dBm - 140 dBu Slow-CW signal not any more detectable with above listed parameters Conclusions: Slow-CW has a 20 dB signal level advantage over normal (aural CW), which means that the minimum detectable and/or readable Slow-CW signal that might just allow communication lies 20 dB below the signal, that can just be detected and/or decoded by a trained CW-operator's ear (yes, I consider myself to be a trained CW operator ...). If I consider the "CW-operator's ear/brain bandwidth" to be 30 Hz, this roughly corresponds to the bandwidths used (0.3 vs 30 Hz). I would be interested to get your comments or own measurements on this subject. I do not yet have sufficient experience with Spectran to make full advantage of this software, so I would like to hear about that software as well. Best 73 Geri, DK8KW (W1KW) From akestelo at bellatlantic.net Sat Apr 15 16:14:55 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:52 2003 Subject: [Lf] 20 dB Advantage for QRS Message-ID: <38F8BFAF.BEAEB12C@bellatlantic.net> "'Geri' Kinzel, DK8KW" wrote: > Hello friends, > > I made some laboratory tests this morning to get some indication about the > ability to communicate with signals below noise level using Slow-CW. > > I used a calibrated frequency synthesizer (Adret 2230), an 0-120 dB > attenuator in 1 dB steps (Schlumberger BMD500) and my Praecitronic MV61 > Selective Level Meter. With a BNC t-connector I fed the normal band noise > including loran lines on 137.500 kHz (+/- 50 Hz) to one side of the > t-connector, and the output of the frequency synthesizer to the other side. > > With the attenuator I made sure that a 0 dBm (50 Ohm) signal with the > synthesizer corresponds to a -80 dBu (75 Ohm) signal at the MV62 > (plus/minus 1 dB). > > The band was quite this morning, with a background noise around -110 dBu > (approx. S 4) and Loran lines clearly visible. > > Using the 100 Hz bandwidth of the MV62 and the cascaded 250 Hz/500 Hz CW > filters of the IC-746 I checked the signal by ear as well as with the > Spectrogram software with the normal parameters I use for "3-5 > second-dot-length" Slow-CW (5.5k sample rate, 16bit mono, 16384 points FFT > = 0.3 Hz resolution, 60 dB scale, 300 ms time scale, 10 x average) and > obtained the following results: > > Injected Received Comment > Signal Signal > Strength Strength > > - 20 dBm - 100 dBu good audible CW signal (approx. S6) > - 30 dBm - 110 dBu CW signal approx. equal to > background noise (S4), just can be copied > - 35 dBm - 115 dBu boundary for aural CW, signal just > detectable by ear > - 45 dBm - 125 dBu good "O" signal in Slow-CW, signal > same level as Loran-lines > - 50 dBm - 130 dBu still good readable Slow-CW signal > "M" > - 55 dBm - 135 dBu Slow-CW just detectable "T" > - 60 dBm - 140 dBu Slow-CW signal not any more > detectable with above listed parameters > > Conclusions: > > Slow-CW has a 20 dB signal level advantage over normal (aural CW), which > means that the minimum detectable and/or readable Slow-CW signal that might > just allow communication lies 20 dB below the signal, that can just be > detected and/or decoded by a trained CW-operator's ear (yes, I consider > myself to be a trained CW operator ...). If I consider the "CW-operator's > ear/brain bandwidth" to be 30 Hz, this roughly corresponds to the > bandwidths used (0.3 vs 30 Hz). > > I would be interested to get your comments or own measurements on this > subject. I do not yet have sufficient experience with Spectran to make full > advantage of this software, so I would like to hear about that software as > well. > > Best 73 > > Geri, DK8KW (W1KW) > Peter Dood replied: Hello Geri > I made some laboratory tests this morning to get some indication about the > ability to communicate with signals below noise level using Slow-CW. A most interesting set of measurements. Most of us who use this mode felt that an it gave an extra 15 to 20dBs but this is the first time I have seen objective measurements. While not giving the same noise improvement described in the pionering work of G3PLX and G4JNT described in the LF Experimenter's Book, Spectrogram and Spectran does provide a convenient compromise that can be managed by us non-techies. I have made some improvements to the antenna and although this gives me an extra 0.5Amps on transmit, the downside is that it has increased the level of the Loran sidebands. While the strength of each of these sidebands is not that high the effect of several hundred of them in a passband of 2.7kHz holds the S-meter at S9! While the fix would be to use a directional receiver antenna, such as that used by Laurie or Derek, with QRSS it is not necessary because of the ability of this mode to read signals between the Loran lines. > I would be interested to get your comments or own measurements on this > subject. I do not yet have sufficient experience with Spectran to make full > advantage of this software, so I would like to hear about that software as well. During the month of tests receiving the 20mW erp from I5TGC over an 1800km path (plus Alps) I found Spectran had a slight advantage (even at its Beta stage) mainly because it has a higher frequency resolution. I used the 0.125Hz setting which placed the Loran sidebands (on average) about 15mm apart, which gives plenty of space to see a signal. The best compromise dot period for 0.125Hz apears to be around 5 seconds. At this stage the Speed Control (integration time?) is not slow enough take advantage of the 0.064 and 0.032Hz settings of Spectran. It would be interesting test these narrower settings to find the limit of the soundcard. Geri, I would be most interested in any tests you may make on Spectran - I take it you have a copy. -- Regards, Peter, G3LDO _____________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf From akestelo at bellatlantic.net Sat Apr 15 19:31:00 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:52 2003 Subject: [Lf] Discussion of the Peter Bobek award, and TransAtlantic II] Message-ID: <38F8EDA4.28817B66@bellatlantic.net> John W Gould wrote: > As one of the prime movers to get the award in place I felt that I needed to > respond to Larry's comments. Firstly, I must make it clear that I totally > agree with Larry's approach. I also ought to say that my views here are my > own, rather than representing those of the RSGB HF Committee. I also > haven't discussed this reply with the other sponsors of the award - the DARC > or AMRAD, though I suspect that they would agree with my line. > > One of the purposes of the award was to remember a modest but determined > experimenter and excellent operator who amongst other significant amateur > achievements was one of the pioneers on 136kHz. The basic idea came from > another determined and successful experimenter who participates in this > list. The award was also put in place to act as a driver for those within > the hobby who use an award to sustain their interest in meeting a specific > goal. Clearly, it will be difficult to meet the terms of the challenge. > Larry is right to remind us that before anyone is successful we may need to > achieve the 2-way QSO at higher ERP. Maybe the guys in the Azores or > Iceland who, for the purposed of the award we decided to exclude, may be > able to add a valuable contribution by demonstrating a 1 watt ERP QSO over > part of the distance. Both steps will help calibrate what is needed to be > done in order to meet the challenge. > > We have to remember that the challenge is optional. I have some fun doing > DXCC on the HF Bands, but I don't do IOTA - that's my choice. My XYL can't > understand why I do amateur radio as the Internet or the 'phone is so much > easier and can be cheaper - but that's another debate! > > Through simple things like lists of records and firsts, awards, some amongst > us have been encouraged to improve their technical and operating knowledge. > Not all - some have drive to do that without the lists, awards, etc. Each > to his/her own. Over the last few years aerial and receiving capability has > improved significantly. Work on information coding and modulation, > developed for other reasons has been successfully applied, e.g. G3PLX, G4JNT > and VE2IQ.... to name but a few of the experimenters. > > It doesn't matter what drives us, but don't let's open up a debate about the > rules for the Transatlantic Challenge. > > I look forward to monitoring the TransAtlantic II activity - I hope that > others are inspired to set up other experiments, whether or not an award or > certificate follows the achievement. > > I probably need an award to transmit LF outside the boundary of my garden! > > 73 > John > > > -----Original Message----- > > From: majordom@post.thorcom.com [mailto:majordom@post.thorcom.com]On > > Behalf Of Larry Kayser > > Sent: Friday, April 14, 2000 10:54 > > To: rsgb_lf_group@blacksheep.org; Mike Dennison > > Subject: LF: Discussion of the Peter Bobek award, and TransAtlantic II > > > > > > Greetings All. > > > > Gentlemen: > > > > I would sincerely appreciate if discussions about the Peter Bobek award in > > any terms of the activities of the TransAtlantic II project be avoided now > > and until after TransAtlantic II results are known at the end of next > > November. > > > > I am very sure that Peter Bobek was a person of honour, and some > > justly feel > > that the award was conceived and now promoted as a recognition of a great > > achievement in LF. > > > > The facts are, that the award requirements must and will have > > ZERO impact on > > how TransAtlantic II will be undertaken from this side of the Atlantic. I > > have only read the award requirements in a most cursory manner > > and will not > > read them again until after we return from VO1 in November. I > > have nothing > > against or for the award, but I do know my focus - have signals heard both > > ways and if possible get a two way QSO across the North Atlantic in > > November. > > > > The simple facts of the matter are, that what we have to do to > > get an LF QSO > > in the amateur LF band across the North Atlantic the FIRST time > > will be many > > dB in excess of what will be required to have the 200th or 2000th > > QSO across > > the North Atlantic on LF. > > > > We can test the results achieved by TransAtlantic II, and wouldn't it be > > wonderful if we could do it with 1W erp, after the test period is > > over. If > > the award requirements have been met then well and good. If the award > > requirements have not been meet this also is well and good. My personal > > feelings are that I would really like to have a serious discussion later > > this year about the qualification for the award, that would mean that some > > signals were heard either way or a completed QSO was achieved > > over the North > > Atlantic..... > > > > Summary, the award does not drive the project, the award is a byproduct of > > the results of the project. > > > > Larry > > VA3LK > > > > > > > > > > From akestelo at bellatlantic.net Mon Apr 17 14:13:25 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:52 2003 Subject: [Lf] 2225 Km on LF ! Message-ID: <38FB4634.DE1EBA1B@bellatlantic.net> G0MRF@aol.com wrote: > Hello Andre' Larry, Mitch, and Jack VE1ZZ. > > Hi. > I've just arrived back home having spent a fair proportion of the weekend at > the Decca site at Puckeridge. > Although I have yet to download the weekends e-mail I guess that our attempt > to span the Atlantic was not successful. > I thought I would just drop you all a quick line to say thanks for your > efforts over the past two nights. Although unsuccessful from a transatlantic > perspective our weekend was a good learning experience. I'm sure Derek etc > will summarise the event on the reflector in due course. I hope listening to > summer static has not done too much damage to your ears! I wonder how Jack > found listening to 137.710 while in close proximity to CFH? > > >From my own perspective I was pleased to work a UB5 station crossband at > 2225km through a daylight path. - Something must be working. - I don't think > his antenna was even optimised for LF. > On a technical front I was surprised by the antenna efficiency and the extra > care needed in an operation of this type. When we first set up the beacon I > arranged for the keyer / drive to be on, but had the 1.2kW PSU wired to a > timer. With the FET driver (4426) powered by 12V but with zero Volts on the > FETs, the residual signal leaking through a 680R resistor and the FETs could > be detected nearly 100km away. I'll measure the power output accurately in > the morning, but I estimate that there was a maximum of 40 milliwatts being > applied to the antenna, which normally wouldn't be a problem, but in this > case about 4mW was radiated. > > An amazing mast, shame it's probably going to be demolished shortly. > > Vy 73 to all, and thank you once again for the time you have spent away from > better things. > > David G0MRF From akestelo at bellatlantic.net Mon Apr 17 14:35:29 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:52 2003 Subject: [Lf] LF: Radiated powers ...] Message-ID: <38FB4B61.BF553AF7@bellatlantic.net> V?in? Lehtoranta wrote: > For those interested on the history of LF/MF coverage planning: > > (An excerpt from a report of > EBU Working Party A, Hamburg, April 1971) > > DEFINITIONS OF RADIATED TRANSMITTER POWER > -- (5 proposals received) -- > > a) Effective radiated power (ERP) - by ORF (J. Burgstaller) > > It is proposed to apply the same definition as the one > used in the VHF and UHF bands. > > b) Equivalent monopole radiated power (EMRP) - BBC (Dr Phillips) > > This definition is based on a short vertical reference aerial, > giving horizontally the same radiation as the actual aerial, > both being assumed to be located on a perfectly-conducting > horizontal plane. The advantage would be that in the present > CCIR Report, the curves would correspond to 1 kW EMRP (!!!) > > c) Equivalent power at a distance of 10 km (EP) - RTE (Mr Curley) > > For MF propagation it would be reasonable to consider the > surrounding countryside up to a radial distance of approximately > 10 km as being part of the aerial system. A practical suggestion > to define the radiated power may be as follows: the equivalent > power required to produce the same field strength at 10 km when > applied at the base of a vertical aerial of one quarter wavelength > equipped with a perfect earth system and moderate conductivity > (3*10E-3 mhos/m) around that aerial up to a distance of 10 km. > > d) Cymomotive force (CMF) - ORTF > > The cymomotive force is defined at any point in the space around > an aerial, for which the fed-in energy is known, related to the > distance of that point from the aerial. The gain of the aerial > must be considered when the field strength is calculated at that > point. The product of the field strength and the distance > is defined as the cymomotive force. > > e) Operative radiated power (ORP) - ARD/ZDF > > This term is defined as follows: "The power supplied to the > antenna multiplied by the gain of the antenna in a given direction > when the reference antenna, placed on the surface of a perfectly > conducting plane earth, produces an unattenuated field strength > of 300 mV/m at a distance of 1 km at any angle of departure > above the plane earth. > ---------------------------------------------------------------- > Note by Vaino: ERP also was there but it was not supported... > > At 03:08 17.4.2000 -0400, Geri wrote:---------------------- > >Hello Dick, > > > >great that you also made your field strength measurements. > > > >>we find at Puckeridge 45W was fed to the aerial on 136kHz and 7.5W on > >73kHz. > > > >The difference between your findings and mine (16 W ERP on 73 kHz, measured > >at nearly twice the distance using a very basic and rough "rule of thump" > >measurment) is only about 3 dB. > > > >Dick, PA0SE wrote: > > > >>This is EIRP and not ERP of course. > > > >Well, kind of. What I thought was a silly question seems seems always to > >have been a point of discussion betwen the experts. Let me quote from an > >e-mail that Vaino, OH2LX has send me as an answer to my question: > > > >>We have not been using the "paper curves" for some time. > >>Many computer GW programmes have been developed but none of > >>them seem to serve us the way we all should expect them to do. > >> > >>Hardly no one was serious with either ERP or EIRP when the > >>"Conditions of validity" for the family of curves were being > >>formulated. There were some 6 or 7 candidates icluding CMF, > >>EMRP and some others. EIRP is rather "fuzzy" and ERP refers > >>to a dipole, so the choice was to be called EMRP: > >> > >>- The radiating element is a short vertical monopole > >> (The equivalent dipole moment is 5(lambda)/2(pii)). Assuming > >> such a vertical antenna to be on the surface of a perfectly > >> conducting plane earth and excited so as to radiate 1 kW, > >> the fiels at a distance of 1 km would be 300 mV/m; > >> this corresponds to a cymomotive force of 300 V. > >> > >>Personally I don't know anyone who wants to make practical > >>field work or reporting in terms of CMF. As you know from > >>practice, the problems are hiding elsewhere. Usually it is > >>most useful to discover a lump sigma value for a ground path > >>with potential adjustments according to seasonal etc conditions. > >>Without reliable looking long term measurements with supporting > >>occasional flight measurements there would be no brain twisting, > >>at least we could not explain all what happens on measurements. > > > >Best 73 Geri, DK8KW (W1KW) > > ---------------------------------------------------------- > V.K.Lehtoranta, OH2LX, POBox 50, FIN-05401 Jokela, Finland > ------ Tel: +358-9-4173965 ---- Fax: +358-9-4173961 ------ > E-mail: vaiski@dlc.fi - alias: oh2lx@dlc.fi & oh2lx@sral.fi From akestelo at bellatlantic.net Mon Apr 17 14:36:53 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:53 2003 Subject: [Lf] Spectran, Spectrogram and extreme QRS - a test ? Message-ID: <38FB4BB4.EA7FA118@bellatlantic.net> Talbot Andrew wrote: > I have not played with Spectran yet, but on the question of dot > length...... > The optimum dot will depend on the FFT and integration time of the > software. Ideally the dot length will be a multiple of the FFT period; > three periods will give perfect resolution unless the software uses too > excessive an interleave factor, two will be adequate but dots could get > masked by impulse noise (an impulse can be several seconds in this > mode). What does the 0.03 Hz refer to, is it the FFT bin size or the > minimum resolution which is usually two to three bins depending on the > window employed. I use either EVMSPEC for the faster rates, or the > Dopplergram software for the EVM for slower monitoring, both have rates > at binary submultiples of 8000Hz. > > 30s dots is still fast CW as far as I am concerned ! > > If your transmitter is REALLY stable, and I mean significantly better > than 0.1ppm / 0.01 Hz and with the frequency known to this accuracy, I > should be able to do an LF Dopplergram on your signal and see what day / > night ionospheric effects are visible. These effects do show up on the > DCF 77.5 kHz signal and 137 should show a lot more. Here the sampling > rate of the signal will be 8000 / (2^18) = 0.03 Hz and a 256 point FFT > allows signal monitoring in a 240uHz bandwidth. It won't take much > notice of the 30 second dot period ! > Andy G4JNT > > >Since we are used to 3 second dots with Spectrogram, it seems > appropriate > >to go to 30 sec with Spectran at maximum resolution. > > >Now, I want to arrange a test, if someone is interested, of course. I'm > >planning to beacon for some days at low power, sending a message with > QRS in DFCW > >mode on 137.790 / 137.792, at 30 sec/dot, with 20 sec interval. > >I will reduce RF power to 10 Watt, giving an approximative ERP of 10 > mW. With > >this power setting my 900W TX will run unattended for days (I hope...) > >, if you have a stable RX with a stable BFO ! From fgentges at mindspring.com Tue Apr 18 18:12:55 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:41:53 2003 Subject: [Lf] Protoype PC boards Message-ID: <38FCCFD7.4BDCD4CA@mindspring.com> LFers, I spotted a web page that looks interesting. Might be like flushing your money down the toilet but.... Look at . They are in Bulgaria. We could get some small PC boards for our LF work here at great prototyping prices. Shipping and funds transfer could be a real pain. Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From akestelo at bellatlantic.net Wed Apr 19 08:17:28 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:53 2003 Subject: [Lf] LF: extreme narrowband modes Message-ID: <38FD95C7.FB2DF5FB@bellatlantic.net> Rik Strobbe wrote: > I just uploaded the 'extreme narrowband modes' page on my website : > > http://www.qsl.net/on7yd/136narro.htm > > I tried to find a compromise between keeping things understandable (minimal > math) and being complete (and correct). > > Comments welcome. > > 73, Rik ON7YD From akestelo at bellatlantic.net Wed Apr 19 20:28:19 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:53 2003 Subject: [Lf] LF: Puckeridge expedition - Interim Report Message-ID: <38FE4113.5885EB9D@bellatlantic.net> DEREK ATTER wrote: > Re: The LF operation from the Decca station at Puckeridge 11th April and > 14/15/16 April - > > Having just about recovered from the weekend's activity and travelling up > to Puckeridge again yesterday (Tuesday18th) to recover the remaining bits > of gear including tables and chairs etc and the loading coil and variometer > used by all of the operating groups involved, I thought that I would post > an initial report of the activity pending a more detailed study of the logs > and incoming reports. > > Firstly, thanks to all those who participated and to all those sent in > signal reports and messages of encouragement. The exercise was arranged at > very short notice and word spead around the LF operators living within > reasonable reach of the site to invite one or two groups of operators to > take part. > Apart from the Decca mast and an RF thermo-couple ammeter , none of the > original equipment such as loading coils etc was used. For 136Khz > operation a relatively small variometer ( about 500uH max) and a tapped > toroidal auto transformer were connected to ground from the copper pipe > lead-in to the base of the mast which is supported on 4 massive ceramic > insulators. The exploratory visit earlier in the week (11th April) allowed > a purpose-built additional loading coil for 73Khz to be built by Lech G3KAU > back at base in time for the main excercise at the weekend. Three > transmitters were employed at various times, the G3GRO 300W much modified > BKE linear amplifier used for the 1W ERP tests on 73/136Khz earlier in the > week and on Friday and Saturday for running between 1 and 5W ERP plus the > well tried G0MRF 500W set-up and the G3YXM 1Kw class-D rig used previously > on many /P expeditions. During the overnight sessions on Friday in beacon > mode the ERP was 50W and 100W ERP overnight Saturday. We had a few > problems to start with in getting the variometer to handle the 500W RF and > we had a few splatts and sparks resulting in VSWR trips until we realised > that the capacitive voltage divider in the forward/reflected power meter in > the variometer was tracking over and by-passed it. Fortunately we had > another SWR meter in line. We also found that an RF sampler unit brought > along by Jim M0BMU very useful in setting up the matching and tuning in > conjunction with an oscilloscope very useful. We realised on Saturday that > the range of our RF ammeter was too small for the high power operation and > rescued the original very large 30A RF ammeter from the pile of redundant > scrap units outside in the rain and pressed it into service. During the > beacon sessions that was reading 14A into the base of the mast which looks > like 5ohms resistive in series with 3750pf ! That represents an RF power > of 1Kw into the antenna or 100W ERP allowing for an overall antenna > efficiency of 10% on 136Khz. > The receive system was a home brew up-converter with an input bandpass > filter of about 3khz bandwidth on both 73 and 136Khz followed by a > mini-circuits MAR6 preamp and MC1496 mixer IC to a 10Mhz IF feeding both a > FT990 and IC756 transceiver for most of the time. The FT990 and converter > stood up remarkably well to the very large antenna input with no sign of > cross-mod. We had a switched attenuator at the input to the converter but > for most of the time it was switched out. That attenuator was used later > for some comparative tests with a small "back-garden " type antenna nearby > which hopefully will be reported on later. We had two operator positions > side by side, one handling the 136 and 73 traffic and the second op also > monitoring 136/73Khz in parallel but also handling the HF cross-band input > mainly from 7.0Mhz. > > Summary of Results : We had about 65 QSOs in total including those during > the initial setting up period on Tuesday 11th of April > already reported. Two-way contacts were made on both bands and cross-band > contacts from136Khz to 73Khz and to 7.0Mhz > There have not been any reception reports from across the pond from VE or W > which was always going to be a long shot, but the longest contact was > cross-band to 7.0Mhz with Alex, UB5WF in Loc KN58JQ about 200Km north of > Odessa on the Black Sea who gave us RST429. normal CW at a distance of > 2225Km ! This was over a daylight path at 12-32 UTC on Sunday 16th. It is > not known yet what RX antenna Alex had for 136Khz but it is highly unlikely > that it was a dedicated LF antenna since there is as yet no LF activity in > Russia as far as is known. Other long distance QSOs were to Valerio, Ik5ZPV > 2-way on 136 who gave us RST589 IK7HSS cross band to 7.0Mhz, and Neils > OZ8NJ (2-way136) who QSPd to us that IK5ZPV was hearing us and would call > us shortly. We also got a RST 599 on 136Khz from Christer SM6PXJ , OZ5N > and Toni HB2ASB. Two QSOs were also made on both 136 and 73Khz to Finbar > EI0CF and Ray GI3PDN. Reports on 73Khz were about 2-S points down with Ray > and Finbar by comparison with 136Khz. We also worked GJ4CBQ and GU3SQX > cross band 136Khz/7.0 Mhz which was pleasing since due to Loran QRM from > Lessay they normally have difficulty in hearing stations on 136Khz. > Perhaps one of the most unusual QSOs was with Graham G3XTZ/M operating > mobile on 136Khz CW whilst driving to the site to have a spell of operating > ! I will post a full list of the QSOs made in the near future when I have > transposed the logs. We have also just had a report via E-mail from Marc > F5MAF in Toulouse, JN03PP who was hearing us at 599+ on a 2 meter diam loop > at a distance of 900Km and bemoaning the fact there is no LF activity in > his neck of the woods. > > Thanks to all those who took part despite the very wet and freezing cold > weather and also to those who took the trouble to give us reports which > have yet to be analysed. At one point on Saturday as the shifts changed > over there were 12 people in the ATU shack at the base of the mast which > much represent a large slice of the active UK LF operators! They were :- > > G3KAU, G3XDV , M0BMU, G0MRF, G3XYM, G3XTZ, G3YSX,, G4GVC, Kate,G4JHI, XYL > GVC, G4TSH, G3LHZ , G3GRO and not forgetting Peter G3LDO holding the fort > back home and Walter G3JKV who efforts made it all possible. > > 73 de Derek Atter , G3GRO ( Also licence holder of > the G3WSC Crawley Club callsign) From pstaupe at uswest.net Sat Apr 22 11:33:47 2000 From: pstaupe at uswest.net (Paul Staupe) Date: Thu Jul 3 13:41:53 2003 Subject: [Lf] Selective Level Meter Recommendations? Message-ID: <3901C65B.25E4AAAB@uswest.net> Hi, I'm planning on purchasing a selective level meter for LF work and am wondering who to contact regarding recommendations. I've been looking at the HP 3586C, and the HP 3746A. Can you point me in the right direction? Thanks, Paul W0AD Minneapolis From halfei at erols.com Sun Apr 23 00:13:59 2000 From: halfei at erols.com (hal) Date: Thu Jul 3 13:41:54 2003 Subject: [Lf] SAQ history from IEEE history society web page. Message-ID: <39026A77.AA929EA4@erols.com> In 1922, construction began in Grimeton, Sweden on a new radio station to establish superior communication links with the United States. At the heart of the Grimeton station was an Alexanderson alternator, the transmitter technology invented by Sweden's own Ernst F W Alexanderson in 1910. With the Alexanderson alternator, manufactured by General Electric and sold by RCA, the Grimeton station was able to begin transatlantic transmissions in1924. At the time of the official dedication, held in July 1925, King Gustaf V declared to Calvin Coolidge that the station would greatly strengthen the cultural and commercial bonds between Sweden and the United States. Seventy years later, the Grimeton station is still operational. Using what is claimed to be the last functioning Alexanderson alternator, the station last year broadcast a message to the IEE's "100 years of radio" conference held in London. In an age when satellite links makes intercontinental communication routine, the alternator provides a stirring reminder of how far transmission technology has come. The station facility is in impressive spectacle. The multiple tuned antenna, carried by six 125 meter masts, each with a 46 meter cross beam carrying the twelve wires that feed the six verticals at the top of each mast, is still preserved. The masts each weigh approximately 130 tons and the twelve antenna wires have a total length of 2,200 meters. All the buildings at the radio station are preserved, including a village for the workers that was built nearby. Can the last surviving Alexanderson alternator be preserved for future generations? The County Council of Halland is working to have the station listed as a Cultural Heritage, thereby giving it legal protection. But protected or not, conservation work is needed to prevent the site from deteriorating. The present owner of the station, Telia Mobitel AB is interesting in developing the site as a science museum, but intensive fundraising is required to realize these ambitions. For more information, please contact Hans Bergfast, L?nsstyrelsen Hallands l?n, Kulturmilj?enheten, S-301 86 Halmstad, Sweden, tel. no. 46 35 13 20 00. From halfei at erols.com Sun Apr 23 00:21:26 2000 From: halfei at erols.com (hal) Date: Thu Jul 3 13:41:54 2003 Subject: [Lf] A serious experiment Message-ID: <39026C36.4AD90318@erols.com> "In 1800 Volta reported placing an electrode in each of his ears and connecting the two electrodes to a series stack of electrochemical cells, whose potential was later estimated at 50 V. He reported hearing "a sound like a boiling viscid fluid" Volta didn't know it but he was within inches of inventing electroshock therapy. Instead, it would have to wait for slaughter house workers in the 1920's to notice their electric shocks, design to stun the animals sensless, sometimes had a calming effect. --H. From DK8KW at compuserve.com Sun Apr 23 05:50:55 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:54 2003 Subject: [Lf] Re: Selective Level Meter Recommendations? Message-ID: <200004230451_MC2-A239-1D87@compuserve.com> Helo Paul, >I'm planning on purchasing a selective level meter for LF work and am >wondering who to contact regarding recommendations. I've been looking >at the HP 3586C, and the HP 3746A. Can you point me in the right >direction? > >Thanks, > >Paul W0AD >Minneapolis I have been using Selective Level Meters for some tim now for LF reception. The ones I am familiar with are probably not available in the U.S., I am using old East German type Praecitronic MV61 and MV62 as well as a more modern Siemens D2108. You can find some information on my homepage http://www.qru.de. I have no experience with the HP level meters you mention. It is important, though, that if you want to use the level meter for listening and not only for signal strength measurments, that the filter bandwidth is wide enougjh. My Siemens only has 20 Hz (which is fine for measuring but not wide enough for listening) and 400 Hz (which is too wide), the MV61 and MV62 have a 100 Hz filter, which I believe is kind of optimum (may 80 Hz would do as well). There is a more detailed article on using level meters as receivers at http://members.home.net/rnewell/fsvm.htm. Best 73 Geri, DK8KW (W1KW) From prinaldo at mindspring.com Sun Apr 23 09:07:19 2000 From: prinaldo at mindspring.com (prinaldo@mindspring.com) Date: Thu Jul 3 13:41:54 2003 Subject: [Lf] Re: Selective Level Meter Recommendations? Message-ID: Gentlemen, I think that Elton Sanders or Frank Gentges might be able to give you a pointer. 73, Paul, W4RI "'Geri' Kinzel, DK8KW" wrote: > Helo Paul, >I'm planning on purchasing a selective level meter for LF work and am >wondering who to contact regarding recommendations. I've been looking >at the HP 3586C, and the HP 3746A. Can you point me in the right >direction? > >Thanks, > >Paul W0AD >Minneapolis I have been using Selective Level Meters for some tim now for LF reception. The ones I am familiar with are probably not available in the U.S., I am using old East German type Praecitronic MV61 and MV62 as well as a more modern Siemens D2108. You can find some information on my homepage http://www.qru.de. I have no experience with the HP level meters you mention. It is important, though, that if you want to use the level meter for listening and not only for signal strength measurments, that the filter bandwidth is wide enougjh. My Siemens only has 20 Hz (which is fine for measuring but not wide enough for listening) and 400 Hz (which is too wide), the MV61 and MV62 have a 100 Hz filter, which I believe is kind of optimum (may 80 Hz would do as well). There is a more detailed article on using level meters as receivers at http://members.home.net/rnewell/fsvm.htm. Best 73 Geri, DK8KW (W1KW) _______________________________________________ lf mailing list lf@amrad.org http://www.amrad.org/mailman/listinfo/lf From akestelo at bellatlantic.net Sun Apr 23 09:43:32 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:54 2003 Subject: [Lf] A serious experiment References: <39026C36.4AD90318@erols.com> Message-ID: <3902EFF4.4273FB7F@bellatlantic.net> hal wrote: > [...] > > Volta didn't know it but he was within inches of inventing > electroshock therapy. Instead, it would have to wait for slaughter > house workers in the 1920's to notice their electric shocks, design to > stun > the animals sensless, sometimes had a calming effect. And of course, we had before him another inveterate tinkerer, Benjamin Franklin, who used to kill chickens by electrocution (attaching them to his kites...) Andre' From fgentges at mindspring.com Sun Apr 23 11:51:01 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:41:55 2003 Subject: [Lf] LF Antenna Report Message-ID: <39030DD5.CA009195@mindspring.com> Hi, Last night I scanned the 1966 NEL "Low-Frequency Top-Loaded Antennas" report provided to us by Boynton Hagaman at the last meeting. This resulted in a series of Acrobat files. They total 4.8 megs in size but all can be put on a 1.4 meg floppy disk. I cleaned up some of the type mainly in the math formulas, cropped out the previous copying artifacts and margin notes from previous copying generations. All in all the scanning and editing turned out to not be all that bad to do. I would like for someone to work through a sample problem of a 60 foot tower at 136 kHz and 6 top hat wires. We could, with his permission, build it at Ted's afterwards and see how well this data scales and how well it really does. Any volunteers? Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From DK8KW at compuserve.com Sun Apr 23 14:21:52 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:55 2003 Subject: [Lf] LF Antenna Report Message-ID: <200004231322_MC2-A249-E2D8@compuserve.com> Hallo Frank, have not had a look at the files you mention (but would love to see a copy). However, exactly the sample you mention would interest me, too, because that is exactly the configuration I use currently on 136 kHz. >I would like for someone to work through a sample problem of a 60 foot >tower at 136 kHz and 6 top hat wires. We could, with his permission, >build it at Ted's afterwards and see how well this data scales and how >well it really does. Any volunteers? Well, not yet 6 top load radials but 5 only. But I plan to increase the number to 6. At 45 degrees inclination, what is the optimum length? Currently I have an efficiency of minus 35 to 37 dB (I measured my ERP to be 30 mW in up to 3 miles distance), does this match with the calculations? Best 73, happy Easter Holidays! Geri, DK8KW (W1KW) From fgentges at mindspring.com Sun Apr 23 23:25:22 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:41:55 2003 Subject: [Lf] LF antennas Message-ID: <3903B092.B3122B95@mindspring.com> Hi, Last night I scanned the 1966 NEL "Low-Frequency Top-Loaded Antennas" report provided to us by Boynton Hagaman at the last meeting. This resulted in a series of Acrobat files. They total 4.8 megs in size but each is small enough to put on a 1.4 meg floppy disk. I cleaned up some of the type mainly in the math formulas, cropped out the previous copying artifacts and margin notes from previous copying generations. All in all the scanning and editing turned out to not be all that bad to do. I also have an IRE article on short antennas which covers T's and L's along with top loaded monopoles. I would like for someone to work through a sample problem of a 60 foot tower at 136 kHz and 6 top hat wires from the NEL report and compare to a T or L. We could, with his permission, build it at Ted's afterwards and see how well this data scales and how well it really does. Any volunteers? Frank K0BRA -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From DK8KW at compuserve.com Mon Apr 24 08:28:22 2000 From: DK8KW at compuserve.com ('Geri' Kinzel, DK8KW) Date: Thu Jul 3 13:41:55 2003 Subject: [Lf] Re: Spectran Beta 2c Message-ID: <200004240728_MC2-A24E-FD6F@compuserve.com> Von: Alberto di Bene, INTERNET:dibene@usa.net An: "'Geri' Kinzel, DK8KW", DK8KW Datum: 24.04.100 12:55 BE: Re: Spectran Beta 2c Hello Geri, yes, there is an answer to your question about the 'fuzzyness' of the display. It all boils down to how Spectran works, and the 'hidden averaging' it does on the received signals. I enclose here following an explanation I gave to Rex Moncur about this subject. He was asking me if/how Spectran does perform an averaging on what it receives. What happens in your case is that when your CPU is more loaded, the overlapping factor (defined below) decreases, and with it the 'fuzzyness'. Feel free to post this message to the newsgroup you mention. 73s Alberto I2PHD ---------------------- ----------------------- attached message ---------------------------------------- Rex, I have been away for a few days, please excuse the delay in answering. In its present implementation, what Spectran does is the following : When you activate the 'Average' push button, a running average is computed on the last five samples, BUT it is applied only to the upper part of the display, i.e. the spectrum-analyser-like waveform. The waterfall is, presently, unaffected by the computed average. This for reasons too long to be explained here. This has already changed in the next beta (almost ready), where also the waterfall is subject to averaging, which is user-selectable, from 1 (no averaging) to 100. But the story doesn't end here. When computing spectra with high resolutions, you are faced with a dilemma : if you update the waterfall only when a completely new set of values are computed, then you might end up with a very slow refresh rate, one update every, let's say, 30 seconds or one minute, which not always is what is desired. To overcome this, the technique of overlapping is used, where you apply a sliding window to the data, reusing a portion of the old data together with some new ones. This permits a much frequent updating of the screen. However, a side effect of this technique is a sort of averaging applied to your displayed data. Spectran applies a variable overlapping factor, continously measuring the CPU load, to keep the CPU near to full utilisation. Hence, also the averaging effect is varying, depending on the instantaneous CPU burden. In the upcoming beta, this has changed, in the sense that you can choose whether continue to use this method, or set a fixed overlapping factor (which of course must be compatible with the cycles your CPU can deliver to the program). Setting this factor to 1 will eliminate altogether whatever averaging is done on the display (and will make your refresh rate slower). Hope this answers your question, 73, Alberto I2PHD -------------------------------- ----------------------- Internet Header -------------------------------- Sender: dibene@usa.net Received: from lmsfw1.emea.ibm.com (d06lmsgate-2.uk.ibm.com [195.212.29.2]) by sphmgaab.compuserve.com (8.9.3/8.9.3/SUN-1.9) with ESMTP id GAA02563 for ; Mon, 24 Apr 2000 06:55:06 -0400 (EDT) Received: from d06relay02.portsmouth.uk.ibm.com (d06relay02.portsmouth.uk.ibm.com [9.166.84.148]) by lmsfw1.emea.ibm.com (1.0.0) with ESMTP id LAA145210 for ; Mon, 24 Apr 2000 11:44:05 +0100 Received: from usa.net (lig32-239-128-97.emea.lig-dial.ibm.com [32.239.128.97]) by d06relay02.portsmouth.uk.ibm.com (8.8.8m3/NCO v2.07) with ESMTP id LAA43508 for ; Mon, 24 Apr 2000 11:55:04 +0100 Message-ID: <390427C6.E283D49A@usa.net> Date: Mon, 24 Apr 2000 12:53:58 +0200 From: Alberto di Bene Organization: Undisclosed X-Mailer: Mozilla 4.72 [en] (Win95; U) X-Accept-Language: en MIME-Version: 1.0 To: "'Geri' Kinzel, DK8KW" Subject: Re: Spectran Beta 2c References: <200004220216_MC2-A220-D2E0@compuserve.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From akestelo at bellatlantic.net Wed Apr 26 09:41:36 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:55 2003 Subject: [Lf] [Fwd: LF: loss resistance measurements] Message-ID: <3906E400.9FB57F90@bellatlantic.net> Rik Strobbe wrote: > >From august 99 to today I measured the enviromental loss resistance of my > antenna. The measurments were done by measuring the TX output power and the > antennacurrent. The known coil losses were subtracted. > Results (all values in Ohms) : > > 17 Aug 99 : 130 31 Aug 99 : 126 > 16 Sep 99 : 128 > 01 Oct 99 : 127 17 Oct 99 : 122 > 11 Nov 99 : 118 30 Nov 99 : 113 > 16 Dec 99 : 110 30 Dec 99 : 108 > 14 Jan 00 : 110 29 Jan 00 : 114 > 15 Feb 00 : 110 28 Feb 00 : 116 > 13 Mar 00 : 112 28 Mar 00 : 128 > 14 Apr 00 : 138 25 Apr 00 : 135 > > >From this data it seems that periods of dry / wet weather have a rather > limited effect on the loss (about 5 to 10 Ohms) while the seazonal effect > (summer / winter) seems to be in the order of 25 to 30 Ohms. > In the past I have measured values as high as 155 Ohms (dry period in > summer) and as low as 105 Ohms (wet period in winter). > The major summer / winter effect can be explained by the high ammount of > 'greenery' around the antenna. > > 73, Rik ON7YD From akestelo at bellatlantic.net Wed Apr 26 18:52:50 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] another approach to LF receivers Message-ID: <39076532.612852F3@bellatlantic.net> Talbot Andrew wrote: > I think most modern transceivers derive all their internal frequencies > from one master oscillator. The IC746 uses a 30 MHz device which at > extra cost can be replaced by a small 1-2ppm ovenned oscillator. This > has excellent stability in practice, and after about 30 minutes warm up > stays within 0.1ppm if room temperature does not change violently. > Exact frequency can be adjusted from a preset on the rear panel. I > haven't done it yet, but this could be easily phase locked to a > frequency standard. > > Alternatively, the conversion LO for an LF transverter can be derived > from this internal signal, thus cancelling out drift at the HF > intermediate freq. Net drift is then the 1ppm (or whatever) but now > only at the LF frequency. Getting respectable...... However, in > practice for LF I use a RA1792 Rx. Again all freqs are derived from one > master - an external 5 MHz source with 10^-10 stability. > > For the narrow bandwidth Rx, if you want to start from scratch what > about this as an outline scheme ? > > Start off with a DDS derived LO locked to a standard oscillator, and > downconvert the LF band directly to 32765 Hz. Make up a ladder filter > using watch crystals - I have a first cut design for a five crystal > device with a bandwidth of 1.1 Hz. Subsequently convert the output down > to 1 - 2 Hz 'baseband', again with a locked LO. A/D convert directly > at a sampling rate of, say, 10 Hz to 16 bit accuracy, again with the > sampling clock locked to the frequency standard and feed the output to a > PC via the serial port or even the parallel port. At this data rate > soundcards are irrelevant and any 16 bit language running in DOS can do > some very advanced signal processing. > If I hadn't got so many other projects and a perfectly good Rx I'd have > a go myself ! > > Andy G4JNT From akestelo at bellatlantic.net Thu Apr 27 00:32:07 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] [Fwd: LF: Re: Transatlantic QRSS] Message-ID: <3907B4B7.1D5A07FD@bellatlantic.net> Peter Dodd wrote: > Alan Melia > >....... If I can copy 10mW QRSS (40 sec dots) from Marco over the Alps and over France > > at 900kms.......... > > Alan seems to be having some success with receiving Marco. Up to now > I have seen nothing from Marco yet when I had a 73kHz/136kHz with > I5TGC Alan could not see Cesare. But what we are learning is the > effectiveness of the technique; and the variability of conditions. At > the we have not been able to correlate the reception of of a distant > QRP station with the magnetic activity from the sun, if there is an R > in the month or observations of QRO commercial stations. > > So, as Alan implies, the same QRSS techniques used with amateur QRO > (circa 1w erp) stations could be used to bridge the 'pond' at any > time provided conditions were reasonable. The obvious solution would > be to monitor a station running in beacon mode with QRSS keying. > >From our experience this requires a lot of very close liaison with > the those involved on both sides of the Atlantic and up to now I have > not seen much evidence of this, although I would be the first to > agree that absence of evidence is not evidence of absence. > > I don't think that you have to mount large 'DXpedition' stations to > succeed in bridging the pond - patience, liaison and application with > the equipment and knowhow we already possess should be enough. > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Thu Apr 27 17:58:15 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] [Fwd: LF: Re: Transatlantic beacon tests] Message-ID: <3908A9E7.4A8304F8@bellatlantic.net> Rik Strobbe wrote: > I think that Andy's (G4JNT) approach to go to milli-Hz bandwidth will be > very usefull in exploring the limits of what we can do with our small > antennas and 1 Watt ERP limit. It may also give us some interesting > information on propagation. > But due to the very narrow bandwidth the 'speed' will also be extremely low. > Practise has learned us that a basic QRSS QSO at 3 sec. dot length takes > about 30 minutes. As 1mHz bandwidth corresponds to a dot length of 1000 > seconds a minimal QSO (exchange of calls and 'TMO' report) will take about > 16 hours. The question is if we will have a 16 hours long period of > ionospheric propagation over a 4000km long path ? Otherwise we will need to > rely on the surface wave and the disadvantge of this is that it has a > 'coaxial cable like' attenuation of 2 to 3 dB per 100km. This means that > you need 40 to 60dB more power (or better SNR) to cover a 4000km path > compared to a 2000km path. > > My opinion is that we should try all possibilities, going from normal-speed > CW over QRSS and DFCW to the milli-Herz techniques that Andy is developing, > in our attempt to cross the pond. > Even within a small community as our 'LF world' there are different groups > of interest. But I see this as a benefit, not as a problem. > > 73, Rik ON7YD From akestelo at bellatlantic.net Fri Apr 28 09:37:35 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] about your "paose" Message-ID: <3909860F.36FC6602@bellatlantic.net> Dick Rollema PA0SE wrote: > E-mail can bring remarkable requests! > > Cheers, Dick, PA0SE > > ----- Oorspronkelijk bericht ----- > Van: azedine aziz > Aan: > Verzonden: donderdag 27 april 2000 23:25 > Onderwerp: about your "paose" > > dear sir, > > I 'm very interested in your paose ! > I like to have one mounted and ready to use . I can't made > it here ,because we dont have the related parts. > Can you sell us one ? (or exchange whith some moroccan > product) > Oualyouddine abdelaziz > 288 orida alia mohammedia > Morocco From crippel at erols.com Fri Apr 28 18:46:43 2000 From: crippel at erols.com (Chuck Rippel) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] European LF MW and WWW Site Message-ID: Here is a European LF/MW site to check out: http://www.mwcircle.org/ ----------------------------- Chuck Rippel, WA4HHG R390 List Co-Administrator Reply to: wa4hhg@amsat.org To learn more about R390A's visit: http://www.avslvb.com/R390A/index.html 1968 Contract Dittmore-Friemuth R390A #38 1967 Contract EAC R390A #2808 with outboard Sherwood SE-3 Sync. Detector 1967 Contract EAC R390A #5295 1967 Contract EAC R390A #5591 1967 Contract EAC R390A #1023 All in regular use as premier Shortwave Broadcast DX Receivers -and- Vintage AM Amateur use -------------------------------- From crippel at erols.com Fri Apr 28 18:51:16 2000 From: crippel at erols.com (Chuck Rippel) Date: Thu Jul 3 13:41:56 2003 Subject: [Lf] DSP-WEAK-SIGNAL list ! Message-ID: For those of you so interested in subscribing to another list: From: "K3PGP - John" To: Subject: DSP-WEAK-SIGNAL list ! Date sent: Sun, 19 Mar 2000 18:03:07 -0500 Those of you using or developing DSP techniques to extract weak signals buried in noise may like to know about the following: ===== >The DSP - Weak Signal list is now up and running! > >To s_u_b_s_c_r_i_b_e visit http://www.qth.net > >Scroll down to dsp-weak-signal > >Enter your Email adr. and click on s_u_b_s_c_r_i_b_e. If you have any problem send an Email direct to me and I'll try to help... John - K3PGP http://www.qsl.net/k3pgp http://www.alltel.net/~k3pgp -==- ------- End of forwarded message ------- ----------------------------- Chuck Rippel, WA4HHG R390 List Co-Administrator Reply to: wa4hhg@amsat.org To learn more about R390A's visit: http://www.avslvb.com/R390A/index.html 1968 Contract Dittmore-Friemuth R390A #38 1967 Contract EAC R390A #2808 with outboard Sherwood SE-3 Sync. Detector 1967 Contract EAC R390A #5295 1967 Contract EAC R390A #5591 1967 Contract EAC R390A #1023 All in regular use as premier Shortwave Broadcast DX Receivers -and- Vintage AM Amateur use -------------------------------- From vdetomasi at tiscalinet.it Sat Apr 29 23:41:42 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:41:57 2003 Subject: [Lf] visiting California Message-ID: <390B5716.41DAE2D2@tiscalinet.it> Hi, I will travel to California for business in the period 14-19 May. I will stay around Palo Alto and Lake Tahoe: is there anybody on the list living in the Bay Area ?!? It would be a nice occasion to talk together about DSP! vy 73 Vittorio IK2CZL -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "You dialed an imaginary number. Please rotate your telephone of 90 degrees and redial". From akestelo at bellatlantic.net Sun Apr 30 20:49:18 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:57 2003 Subject: [Lf] visiting California References: <390B5716.41DAE2D2@tiscalinet.it> Message-ID: <390CC67E.4773B588@bellatlantic.net> Hello Vittorio, I would imagine that the two most likely suspects in California would be Cliff and Bill, to whom I am sending a copy of this e-mail 73 Andre' N4ICK ************************* Vittorio De Tomasi wrote: > Hi, > I will travel to California for business in the period 14-19 May. I will > stay around Palo Alto and Lake Tahoe: is there anybody on the list > living in the Bay Area ?!? It would be a nice occasion to talk together > about DSP! > > vy 73 > > Vittorio IK2CZL > -- > ************************************************************************* > Vittorio De Tomasi ik2czl@amsat.org > Home page: http://space.tin.it/scienza/vdetomas > My DSP page: http://www.freeyellow.com/members/padan > > "You dialed an imaginary number. > Please rotate your telephone of 90 degrees and redial". > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf From dsp at hifidelity.com Mon May 1 16:04:47 2000 From: dsp at hifidelity.com (Steve Dove) Date: Thu Jul 3 13:41:57 2003 Subject: [Lf] BBC 198kHz information Message-ID: <390DD54E.7CFC777F@hifidelity.com> Greetings, I don't know if anyone else noticed how loud the Euro Longwave broadcasters were earlier this weekend. It provided this recovering Brit an opportunity to listen to BBC Radio 4 'armchair copy'; the World Service is nice but second-hand via Antigua or Sackville is no substitute for straight-in-the-vein domestic programming from those big sticks next to the M5 near Brum. Coincidentally, a few days ago I was indulging an office clean-up (done every decade or so, whether it needs it or not) and came across an ancient proceedings book of an IBC conference; one of the papers concerned the then recent (early eighties) refit of the Droitwich LW station by Marconi. In addition to some insights to the (again, then) revolutionary PWM-modulated transmitters and detail sketches of the valves-to-combiner-to antenna matching arrangements, there is a little drawing of the changes made to the antenna and a comparison graph of the R/X before and after. Ever sensitive to copyright issues, I nevertheless don't feel that anyone's interests are going to be dented or that Legs Luigi will be after my hide, or worse, if anyone on the list here is sufficiently interested in a copy. Macaroni have been out of the big transmitter business for a while now, anyway. Interestingly, given the Beeb's 25-year re-equip cycle, they're probably starting to figure out what to do next time round . . . Cheers, Steve W3EEE / G3YDV From akestelo at bellatlantic.net Mon May 1 22:58:58 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:57 2003 Subject: [Lf] GPS SA going away!] Message-ID: <390E3662.FBB299E@bellatlantic.net> Clifford Buttschardt wrote: > In the next few days, we should be getting an announcement that the > selective availability system will be either turned off or reduced in > some fashion. See http://www.igeb.gov/ > Cliff K7RR From akestelo at bellatlantic.net Mon May 1 23:08:03 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:58 2003 Subject: [Lf] The Covert Comic ? Message-ID: <390E3882.C6CFBA1C@bellatlantic.net> Additional material available at http://www.covertcomic.com/CovertComicUpdate.htm From akestelo at bellatlantic.net Tue May 2 08:24:25 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:58 2003 Subject: [Lf] Telsa Coils Message-ID: <390EBAE8.FDE6D286@bellatlantic.net> Peter Dodd wrote: > Yesterday, Monday, I operated from GB2CPM, not on LF but at the HF > permanent amateur station that forms part of the radio section of the museum. > At the Electricity Hall a group of Telso Coil builders had converged > for a Telsa coil session. This comprised two groups, an indoor > exibition using small coils ranging from 10cm long to 1m long; and > the second group with the big coils (up to 2m long) which had to be > done outside because of the very high voltages they produced. > The indoor goup had the advantage having a large room that could be > darkened allowing the spectacular display to bee seen to its best > advantage. The room had to be ventilated between sessions to clear > out all the ozone! > The outdoor group set up a test area in the afternoon, starting by > digging a cruciform shaped trench and laying down a lot of copper > tubing and soaking it in brine before filling it in. The components > of three large coils arrived in special vans and I was able to watch > and photograph these coils and the electrical control and power > systems being assembled. > > The length of the main coils of the larger Telsa machines ranged from > 1 to 2m with a length/diameter ratio of around 3:1. The inductance of > the main coils ranged from 400mH to 1.2H depending on the size of the > machine. All coils seemed to be close wound with 1mm enamelled copper > wire. The primary coils were made of 10mm copper tubing with clip > connections for 'tuning'. > > This main set of experiments had to be done after the museum had > closed to the public and when it was getting dark. The corona > discharge from 1meV machine was truely spectacular and made our hair > stand on end! > > I was much taken with the technology of these machines, particularly > the care with which the coils had been wound and the construction of > high capacity high voltage capacitors. Some members of the group were > interested in our activities in a similar technology. > > If you want to know more about the Telsa Builders activities see > > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Wed May 3 08:26:27 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:58 2003 Subject: [Lf] PKZIP Message-ID: <39100CE3.190D362C@bellatlantic.net> PKZIP AUTHOR DIES by Dave Murphy, member@itrain.org Phillip W. Katz, 37, died on April 14 from complications arising from a long-time illness. As a young man, Katz released the PKZip file compression program in 1986. The program revolutionized the world of Bulletin Board Systems (BBS) and the fledgling Internet. I remember getting my hands on the very first public version. I was able to compress copies of my dBASE, Lotus 1-2-3, and WordPerfect files on to a single diskette. All I had was an IBM PC-XT and an IBM PC Portable ... storage space was at a premium. As new versions were released, I'd eagerly download the updates and rezip my files just to get an extra five percent more compression. When transferring files online with my high-speed Hayes 1200Kbps modem, every bit of extra compression meant a few minutes saved. I even got to try the program before I paid for it. PKZip was the first shareware program I ever registered. Katz became famous for pioneering the shareware concept of software distribution. Users were invited to download and try new software. Only if they liked the program and decided to continue using it were they obligated to purchase the software. Phil, I never met you in person, but I'll miss you. From akestelo at bellatlantic.net Wed May 3 08:35:51 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:58 2003 Subject: [Lf] Earth contact resistance Message-ID: <39100F17.1996D9CA@bellatlantic.net> Alan Melia wrote: > Hi all, I have noted again from Peter's description of the Tesla experiments > at the Museum, and from John's Earth Wireless web site, that the addition of > several pounds (or kgms) of common salt (and water) seems to be a usual way > of improving the contact resistance beween earth rods and the surrounding > ground. It occurs to me that those with an enviromental approach or just > those who are keen gardeners (I note the reluctant pruning near the > aerials!) might not wish to blight their garden with large quantities of > sodium chloride. I have seen somewhere in radio literature that Gypsum is > almost as good in the electrical parameters and is actually beneficial > horticulturally. It is much less soluble than salt and for the same effect > will not need quite so many repeated treatments (It may not yield quite such > a low resistance). I suspect its worth a try as Gypsum ( Calcuim Sulphate) > is available from most Garden Centres. > > "I am just top dressing the lawn dear...." when decreasing the > resistance of the earth-mat you surreptitiously buried under > it.............. It could just be worth an extra helping of chocolate fudge! > > Cheers de Alan G3NYK > Alan.Melia@btinternet.com From akestelo at bellatlantic.net Wed May 3 08:41:50 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:59 2003 Subject: [Lf] Transatlantic 2 Message-ID: <3910107E.2B001A7D@bellatlantic.net> G0MRF@aol.com wrote: > Hello All > > In about 3 weeks I will be travelling from Dayton Ohio to meet Larry and > friends in Niagara to discuss LF and in particular his plans for this > Novembers attempt at crossing the Atlantic. > This is a useful opportunity to ensure that, come November 10th, we are all, > As a friend of mine from Londonderry once put it. -singing from the same hymn > book. > > During the last two periods of transatlantic testing we had the luxury of > switching the transmitters on and leaving the hard work to Andre' and friends > on a cold wet beach on the American East Coast or recently, to Larry Mitch > and Jack listening to static > > This time, with everyone eagerly anticipating a two way QSO, there is a much > greater potential for success and a much greater chance of complete chaos. > Hopefully we can jointly agree on appropriate operating standards and > practice. > > In the past few weeks there have been a number of views expressed on the > reflector and in private e-mails which suggest that there are a variety of > thoughts on operating procedures for the tests. Modes, times, frequencies, > schedules etc are all open for debate. I have been asked to arrive in > Niagara with some collective thoughts for Larry to consider. While I'm sure > that this discussion will eventually find it's way onto the reflector, it > would be advantageous to have an initial exchange of views and set some basic > guidelines prior to Autumn. > > Can I suggest that the following topics represent a starting point. If you > have any views please express them, - Even if it's just to confirm the > obvious. > Even a brief yes / no response will help. > > Modes. > We all know and appreciate the benefits of QRSS. Spectrogram is well known > and spectran is becoming tried and tested, albeit with a small question mark > over the jumps in the display which seem related to processor loading. Is > QRSS the only way? Presumably optimum dot speed will depend settings and > propagation. > It's easy for us, but it's also possible Larry may want to trade off > bandwidth for the ability to see more than one potential QSO on his monitor. > Or have >1 system running. > > Should we try a period of very slow techniques as pioneered by G4JNT and > G3PLX? > > Some stations seem determined to stick with normal CW. How / can we embrace > this diversity. > > Much praise has been voiced of Bill, VE2IQ's, BPSK software. It certainly has > the ability to operate with weak signals and the 'grab' facility means you > could leave the station on remote ( and get some sleep) Larry has expressed > the opinion that this can work with class D transmitters, but after the > Puckeridge key click saga and with no practical experience in the UK at high > power, this should be examined before any use is made of the mode. > > FREQUENCIES > > I suspect the numbers of stations participating will exceed previous levels. > > With CFH active, Larry will only have the top part of the band. - I'll try to > find the limits to this when we meet. > Larry's group will advise of specific frequencies that are clear, or > frequencies to be avoided. This may not happen until the VO1 receive team is > up and running. Hopefully we can devise a fair system of transmitting > frequency allocation within a short period of time. > > We will only have to receive on one frequency. - So no problem there (!?) > Should we select a frequency that's clear on the UK S.Coast as that seems to > be the area with most QRM? Suggestions pse. Although I guess this could wait > until the 'LF Convention' so the information is up to date. > > What is a minimum separation between Tx frequencies? It's important that we > all have sufficient frequency accuracy and stability to avoid drifting into > each other. Should we allocate frequencies so that geographically adjacent > stations are not allocated adjacent frequencies? Or do we plan scheduled > transmission periods. (see below) > Do OH1TN / Europeans wish to participate. - Any indications in QSOs / e-mails? > > SCHEDULES. > Some other weak signal modes run skeds that have prearranged transmission and > reception periods. e.g. Moonbounce and Meteor Scatter. > This has the advantage of totally avoiding QRM. You know when you switch to > receive, you will only hear DX > The periods used with EME and MS vary from 1minute to 5 minutes. Clearly > this is not suitable for QRSS. But what period would be? 2 callsigns etc? > The last time I monitored a transatlantic test it was impossible to receive a > truly weak signal at the same time as another station was transmitting. > Unless you are really lucky you will have someone running a lot of power > within 50 miles. Your receiver may have an AGC which you can switch off but > can you access the AGC in your sound card? > > MAKING THE QSO /S > I guess that as your call is seen in VO1, your phone will ring! OK? > If we take the independent approach this will not be a problem. - You just > carry on as normal. However, If we are running synchronised Tx/ Rx periods do > we break the receive period timing to complete the QSO? or wait for the next > scheduled transmission period? > > Please feel free to copy this to other individual members of the LF community > that you feel may be interested. > > Any additional thoughts? Any qustions for the VE's? > > Thanks for your time. I look forward to the replies. > > 73 > > David G0MRF From akestelo at bellatlantic.net Wed May 3 09:06:13 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:59 2003 Subject: [Lf] Improved QRS pgm ? Message-ID: <39101635.E3C004D@bellatlantic.net> Rik Strobbe wrote: > Hello Marco, > > I will see what I can do to adapt QRS, I will have to use the parallel port > for power switching as all 'output pins' off the serial port are alrteady > in use. > Alternative I could try to put some softawre in a PIC16F84 processor, I > already have some 'beacon software' for it, just have to change speed and > add the power switching. I am willing to send you a programmed PIC on a > ready-to-use PCB. This would have the advantage that you do not need your > PC for it. > > Regarding power switching and the WX-related detuning : > It should be possible to built a small class-D TX and adjust the > powersupply voltage to regulate output power. If we incorporate some > feedback from the amp-meter to the voltage regulation it should be possible > to have a TX that runs at constant antenna current (= constant ERP). > > The above are just some thoughts and a lot of work will be involved it we > want to realize it. So maybe we first have to check if there is enough > interest from the 'listeners side' and if we can share the work, it > wouldn't be fair if we expect you to do it all. > > 73, Rik ON7YD > > >>At the risk of being 'greedy' I would suggest following to Marco : would it > >>be possible to have a series a characters at reduced power after the call ? > >>eg. : 'IK1ODO X Y Z' where IK1ODO is tranmitted at 10mW ERP, X at 5mW ERP, > >>Y at 2.5mW ERP and Z at 1.25mW ERP (of course any other 3 characters can be > >>used). > >> > >>73, Rik ON7YD > >> > >Rik, I will take this seriously. What about writing a modified version of QRS > >to command an attenuator and step power levels? > >I may build a linear amplifier, of some 10W output, and reduce the power > >in four steps of 5 dB (3W, 1W, 300 mW, 100 mW for instance). > >The big problem is to have an automatic tuning. I started the beacon > >on Thursday evening, then left home Friday, and it was raining; so I had to > >raise the power, since the aerial current was down from the nominal. > >The rain stopped on Saturday, and the antenna current rose to (probably) > >+5 dB respect to Friday evening. I was not able to transmit a fixed power > >level; > >my station currently can't run unattended (in effect, my wife was attending > >and checking for smoke, HI). > > > >I returned home by Tuesday, and found the tuning of the variometer > >completely different from Friday. > > > >Thanks to all for the reports. I think we have to go on. > > > >Well, Rik, what signal may we use to change the power levels ? go to > >the parallel port, or use an UART on the serial ? > > > >73 - Marco IK1ODO > > > > > > From akestelo at bellatlantic.net Wed May 3 09:17:11 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:41:59 2003 Subject: [Lf] Re: LF: beacon power control References: <3.0.1.16.20000503100301.2e77a8b0@mail.cc.kuleuven.ac.be> <4.1.20000502224757.020c4040@mailer.inrete.it> <3.0.1.16.20000503132834.2d4fcc54@mail.cc.kuleuven.ac.be> Message-ID: <391018C6.7DEFD53B@bellatlantic.net> Rik Strobbe wrote: > [...] > As the beacon is meant to be low-power (10mW and less) a relative small TX > power can be used (50 Watts and less), so it can easily be overdimensioned > to provide extra safety. Maplin has a small class A amplifier using a LM 1875 that easily puts out 25 watts at 136 Khz. It is stable, has automatic current limiting and overheating protection Because it operates in class A, the output can be controlled simply by a step attenuator at the _input_ of the amplifier. Just a thought 73 Andre' N4ICK From Hansell.Bill at HQ.NAVY.MIL Wed May 3 17:52:16 2000 From: Hansell.Bill at HQ.NAVY.MIL (Hansell, William R.) Date: Thu Jul 3 13:41:59 2003 Subject: [Lf] GPS SA going away!] Message-ID: <101FD8F40D2BD311911000805FA766D904B14C80@pntmsg1.hq.navy.mil> The GPS desk here at OPNAV just told me SA was turned off on 1 May by order of the President. Bill KD1ET -----Original Message----- From: Andre' Kesteloot [mailto:akestelo@bellatlantic.net] Sent: Monday, May 01, 2000 9:59 PM To: AMRAD Tacos; lf-amrad Subject: [Lf] GPS SA going away!] Clifford Buttschardt wrote: > In the next few days, we should be getting an announcement that the > selective availability system will be either turned off or reduced in > some fashion. See http://www.igeb.gov/ > Cliff K7RR _______________________________________________ lf mailing list lf@amrad.org http://www.amrad.org/mailman/listinfo/lf From akestelo at bellatlantic.net Thu May 4 08:36:07 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:00 2003 Subject: [Lf] Beacon Power control.] Message-ID: <391160A7.11BA6727@bellatlantic.net> Johan Bodin wrote: > Hello, > > Compensating an off-resonance antenna with increased TX power > seems like a brute force method to me. Why not build a simple phase > measuring thing that outputs a +/- voltage that is proportional to the phase > relationship between voltage and current in the feeder? After all, the > theoretical definition of resonance is that the voltage and current are in > phase with each other. > > Assuming zero output at 0 degrees, the output from the "phase > sensor" can be used to control a servo motor on a variometer which > brings the system into perfect resonance whatever the wheather... > An op-amp in the servo loop, surrounded by suitable R's and C's, will > make the system slow and stable (dominant pole). It doesn't have to > be faster than the changes in wheather ;-) > > One of my ideas for a "phase sensor" is: > > The feeder voltage and current can be sampled with a resistive (or > capacitive, or both) divider and a current transformer, respectively. > These two signals are then amplified and clipped to square waves. > If these signals are fed into an XOR gate (74HC86 etc), the output > from the gate will be a PWM signal that is proportional to the absolute > value of the phase error. The PWM signal can be converted to a DC > error signal by a simple RC lowpass filter (136 kHz >> the servo loop > bandwidth). The sign of the error signal can be found by connecting > these two signals to a D-type flip-flop (74HC74, 4013 etc). > The current and voltage squarewave signals are connected to the > clock input and the D inputs respectively. The sign bit will appear on > the flip-flop Q output. This sign bit controls the direction of servo motor > travel and the filtered PWM from the XOR gate is the magnitude of the > error. > > Depending on actual implementation, some kind of "gating" may be > needed to prevent the servo loop from "run-away" during key-up periods.. > > Just an idea... > > 73 de Johan SM6LKM From akestelo at bellatlantic.net Thu May 4 14:41:17 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:00 2003 Subject: [Lf] LF: Spectran accuracy Message-ID: <3911B63D.B7E86B91@bellatlantic.net> Talbot Andrew wrote: > Another problem with soundcards is that of timebase accuracy, and in > some cases even stability. Many cases of severe errors were identified > by G3PLX during the development of PSK31 > > In the better cards (real Soundblaster compatibles) the frequencies are > derived from dedicated correct frequency crystals so the CD sampling > rates derived from 44100 Hz are exact (well, within crystal accuracy > anyway). The 8 kHz rate is a different matter though. This cannot be > derived exactly from the same xtal as the 44k1 rates, and an > approximation is often taken by selecting the nearest integer divide > ratio. Errors seen here amount to several Hz at 8 kHz depending on the > individual chip set in use. The best cards have a separate xtal for > this rate and the exact frequency is generated. > > Some SB hardware built onto PC motherboards uses whatever crystal is in > the PC (often the 14.318 MHz one) to generate the SB sampling rates. > Again with integer dividers errors of several Hz can be seen. > > The worst, according to Peter, is a CR controlled system. I have never > seen anything this bad and the story may be apocryphal, but he has had > errors of many 10s of Hz at 8kHz reported. > > I have checked the following : > 1) Older 16 bit true Soundblaster - all sampling rates exact > (meaning within about 10 parts per million of the true values) > > 2) Newer PCI bus compatible true Soundblaster - ditto. > > 3) Onboard SB hardware on a wide range of Dell pentiums (Pentia ? > :-) - 44k1 derivatives 'exact'. Errors from 0 to 6 Hz on the 8 kHz > rate depending on age / type of machine. > > 4) Toshiba satellite laptop - 44k1 derivatives 'exact' , 8 kHz > rate - 7 Hz error > > PSK31 has a calibration routine built in to take out this sampling rate > error and store the calibration constant. But with the temperature > ranges that PCs go through from turn on to several hours of operation, > the crude packaged oscillators they use can easily move a few 10s of > PPM. At 8 kHz this drift alone is several times the minimum Sprectran > resolution and a few Hz initial error is off the scale without > calibration ! > > Andy G4JNT > > > >>Further I noticed that launching another application while running > > Spectran > > >>caused a kind of 'frequency shift' (see screenshot at my webpage). > > >> > > >Alberto found this same problem, but he says that debugging will be > > difficult, > > >and will probably take some time. Incidentally, he is releasing a new > > "beta" > > >version (beta3). > > > > Just to straigthen things a bit up : we are talking of two different > > problems : > > > > 1) The frequency error Marco is talking about, is known to me since > > some time, > > and it is caused by a wrong initial design assumption of Spectran, > > i.e. that the > > frequency ruler scale must start at an integral multiple of 1 Hz. > > This because at > > that time Spectran was meant for EME use, where sub-Hertz > > resolutions are not > > needed. Now that with beta 3 we can do down to 21 milliHz, this > > must revised. > > > > 2) The frequency shift observed and reported by Rik and Alan, is a > > completely new > > thing, for which, at the moment, I have no explanation. I saw, one > > time only, a shift > > of 0.5 Hz, which I attributed to my RX. I wasn't launching or > > using any other > > application at the moment. As this shift has been signalled by > > more than one person, > > and on signals locked to some standards, then I must investigated > > into it. > > > > Thanks for those reports, and don't be shy to send others. The very > > first reason for > > putting out a beta before the final release was just to receive this > > kind of reports. > > > > 73s > > Alberto I2PHD > > ----------------- > > > > > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From akestelo at bellatlantic.net Mon May 8 20:47:51 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:00 2003 Subject: [Lf] surface mount stuff Message-ID: <39175227.97A55A85@bellatlantic.net> Dave wrote: > John. > > > What about telling us how to do it - I refer to 64 pin Surface Mount > > Devices? > > I had the advantage of a quick "course" on surface-mount installation by a > sales rep for a soldering-iron company! The secret to installing the things > is to use a flux-pen and coat all the legs and pads with flux. Excess solder > then just runs off and doesn't tend to "stick" between the legs. The final > trick is to use an iron with a concave bit, I think Weller now do one, this > draws solder into its dimple and, in conjunction with the flux, makes it > easy to clean away solder bridges. You just run the tinned iron along the > row of pins and Bob's yer uncle! Well... if your lucky! I still spent a long > time with a powerful magnifying glass, checking every pin. > > 73. Dave G3YXM. From akestelo at bellatlantic.net Thu May 4 18:39:08 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:00 2003 Subject: [Lf] Magellan GPS Message-ID: <3911EDFB.3EF7CD73@bellatlantic.net> Andy Talbot wrote: > Unfortunately Magellan appear to be the odd ones out on GPS receivers. I > have a Magellan Trailblazer, circa 1993-4 which is almost certainly similar > to yours, and there is no trace of a 1 PPS signal inside the unit; I > searched very hard for it ! In the end I gave up and bought a Garmin GPS25 > module from TAPR. That turned out to be a good move as the device is very > very much better at locking up (1 minute fom cold instead of up to 20 > minutes) with more info available in the NMEA sentences - and of course the > 1 PPS. > > Since SA was turned off, over the last two hours the mean position of my > house has drifted just 2 metres RMS with an absolute worst case shift of > 3.6m. I reckon that with a locking system like the Shera one and a good > stable ovened VCXO, a frequency standard to rival Rubidium and verging on > Caesium accuracy may now be possible. Getting a good enough VCXO will be > the difficult part. > > Andy G4JNT > > -----Original Message----- > From: Alberto di Bene > To: rsgb_lf_group@blacksheep.org > Date: 04 May 2000 16:53 > Subject: Re: LF: GPS Signals Accurate Now!!! > > >While we are discussing GPS, I have a question for all of you. > >I bought a few months ago an OEM 5000 GPS board, made > >circa 1993 by Magellan, because someone had told me that > >on the interface there were available the 1 pps signal derived > >from the received signals from the satellites, with the accuracy > >and stability of their Cesium clocks, +/- the SA. > > > >I was intending to homebrew something similar to the Shera > >project appeared in a past issue of QST. > > > >I have been unable to find that 1 pps signal, however. It just seems > >not to be present on the interface. But there is a hope. > >A few pins do not have signal on them, as seen on the 'scope, > >but they have traces on the PCB leading somewhere. My last hope > >is that the 1 pps signal must be enabled by some command to the > >GPS unit. > > > >Can anybody shed some light on this ? Anybody on this list that > >has experience with the Magellan OM 5000 ? Thanks for any advice. > > > >Alberto I2PHD > > > > > > From dlwilson at erols.com Wed May 10 08:26:04 2000 From: dlwilson at erols.com (David L. Wilson) Date: Thu Jul 3 13:42:00 2003 Subject: [Lf] Magellan GPS In-Reply-To: <3911EDFB.3EF7CD73@bellatlantic.net> Message-ID: <4.1.20000510072202.0091c450@127.0.0.1> At 05:39 PM 5/4/00 -0400, you wrote: ... >> Since SA was turned off, over the last two hours the mean position of my >> house has drifted just 2 metres RMS with an absolute worst case shift of >> 3.6m. Note that 2 hours is far too short to get an accurate error estimate and that long term errors make usiong the mean possition not an accurate way of estimating the true position. Doing either of those will cause the error to be under estimated. See http://www.erols.com/dlwilson/nosa.htm for the results using a Garmin 12XL for 3 days at a surveyed point. I From akestelo at bellatlantic.net Wed May 10 08:48:53 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:01 2003 Subject: [Lf] Re: Question References: <032701bfba42$3fdcb520$bc6daccf@win.net> Message-ID: <39194CA5.784989F@bellatlantic.net> Hello Randy, See QEX, May/June 2000, pp. 13-22 Also note that there is "bpsk" option in PSK31 that greatly enhances reliability 73 Andre' Randy Mays wrote: > Hi, Here is a question from a friend in Los Angeles... "I'll > bet you can answer me a 'technical question' re PSK31 that nobody > seems to know! Of all the digital modes, which is best for long-haul > DX > S/N performance? I'd bet that PSK31 falls apart after some fixed > distance > due to phase distortion in the propagation path, such as long-paths or > > paths over the poles, yes? For brute-force best S/N over such paths, > which digital mode would work best? I had liked PSK31 for its tiny BW, > > but the phase probably kills it. Whats preferrable when using HF or > 6-meters? Any advise you can give would be greatly appreciated!" > What's the answer?? Thanks. Randy > From akestelo at bellatlantic.net Thu May 11 10:02:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:01 2003 Subject: [Lf] New coil design program by G4FGQ Message-ID: <391AAF7C.2B186FE2@bellatlantic.net> > G4FGQ has written a new coil design program, solnoid2.exe. > > It seems to predict loss with better accuracy than solenoid.exe. > > http://www.btinternet.com/~g4fgq.regp/ > > http://www.btinternet.com/~g4fgq.regp/page2.html#S209 > > 73 > Johan SM6LKM From akestelo at bellatlantic.net Fri May 12 09:42:09 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:01 2003 Subject: [Lf] LF: QRSS and QRN] Message-ID: <391BFC20.378633AD@bellatlantic.net> Mike Dennison wrote: > > >From Dave G3YMC > > If Spectran and the other programs offer the capability to copy stations > > 20dB below noise, in these circumstances this would only take you to s9, > > which was certainly copyable with normal CW. I admit the static levels > > recently have been much higher than usual, and would not expect anyone to > > attempt to work transatlantic under such conditions (or to even ragchew!) > > I have two weakish carriers on the band, 136.7 and 137.8 which are > > normally just above the noise. I wonder how copy of these is on Spectran > > with 20dB over heavy static - I can just about copy traces here in the > > crashes. > > This misses the point. Spectrogram etc can copy CW up to 20db > below 'normal' noise. But the duty cycle of static is much lower > than noise, therefore there is a =much= greater advantage than > 20dB. Using Spectrogram and QRSS, I can receive signals 100% > in heavy static that would be impossible to read using normal CW > at whatever speed. > > But in any case it is really up to the individual operator to use > whatever technique he feels happiest with, and regardless of what > technique is used, S9+ QRN is going to degrade it. Also QRSS is > no good for ragchews, no matter how good the S/N is. > > I will try to demonstrate the advantage of QRSS in static by > providing a WAV recording and Spectrogram plot on my web site > (which make me the only LF operator hoping there's QRN tonight!). > > Mike, G3XDV (IO91VT) > http://www.dennison.demon.co.uk/activity.htm From akestelo at bellatlantic.net Fri May 12 09:49:10 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:01 2003 Subject: [Lf] [Fwd: LF: RE: QRSS and QRN] Message-ID: <391BFDC6.1D6D542C@bellatlantic.net> Talbot Andrew wrote: > The static crashes are only " 20dB over 9" for the few microseconds > while they are happening. When using Spectran etc. try turning off the > AGC completely and just allow the static crashes to overload the > receiver for their duration. The Rx will continue working normally > between the crashes and should allow through the signal for processing > at normal strength. Leaving the AGC operating just destroys receiver > gain during its hang period. I find that for almost any radio > monitoring activity manual gain control is better than AGC operation. > > Andy G4JNT From fgentges at mindspring.com Fri May 12 10:41:25 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:02 2003 Subject: [Lf] RE: QRSS and QRN References: <391BFDC6.1D6D542C@bellatlantic.net> Message-ID: <391C0A05.C3AD1BD6@mindspring.com> Hi, Andy is on the right track. A manual AGC with gain control adjusted to clip just a bit above the signal may be optimum in the presence of sferics. The US Navy Verdin VLF system had that feature. Perhaps better yet is a noise blanker with a wideband impulse detector adjusted to take out those few microseconds that trash the receiver so badly. We at AMRAD need to think about how we can make LF "all season" so we can work with and through all this. I was down at Nags Head last weekend and heard quite a bit because no storms were trashing the band so the propagation is there. Sferics is our new frontier. Frank K0BRA Andre' Kesteloot wrote: > > Talbot Andrew wrote: > > > The static crashes are only " 20dB over 9" for the few microseconds > > while they are happening. When using Spectran etc. try turning off the > > AGC completely and just allow the static crashes to overload the > > receiver for their duration. The Rx will continue working normally > > between the crashes and should allow through the signal for processing > > at normal strength. Leaving the AGC operating just destroys receiver > > gain during its hang period. I find that for almost any radio > > monitoring activity manual gain control is better than AGC operation. > > > > Andy G4JNT > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From akestelo at bellatlantic.net Sat May 13 21:02:29 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:02 2003 Subject: [Lf] [Fwd: LF: beacon power control] Message-ID: <391DED15.A53BD8A2@bellatlantic.net> Rik Strobbe wrote: > Hello Andr?, > > Apart from having the different powerlevels Marco has als the problem that > he has to retune his antenna when the WX changes. This is a problem when he > is running an unattended beacon. Therfore I suggested to have some feedback > from the amp-meter (antennacurrent) in order to have always antennacurrent > (= same ERP) at the different powerlevels, independent from WX. > Meanwhile I received mails from 2 other OM that are interested to install > low-power beacons, so it might be a good idea to develope a beacon > providing constant ERP (indepent from antenna detuning) levels. > Any interest for this project in the US ? > > 73, Rik ON7YD > > At 08:17 3/05/00 -0400, you wrote: > >Rik Strobbe wrote: > > > >> [...] > >> As the beacon is meant to be low-power (10mW and less) a relative small TX > >> power can be used (50 Watts and less), so it can easily be overdimensioned > >> to provide extra safety. > > > >Maplin has a small class A amplifier using a LM 1875 that easily puts out 25 > >watts at 136 Khz. It is stable, has automatic current limiting and > overheating > >protection > >Because it operates in class A, the output can be controlled simply by a > step > >attenuator at the _input_ of the amplifier. > >>Just a thought > >>73 > >Andre' N4ICK From akestelo at bellatlantic.net Sun May 14 13:35:23 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:02 2003 Subject: [Lf] LF: IK1ODO 3-level beacon Message-ID: <391ED5CB.F4D1AA0E@bellatlantic.net> Alberto di Bene wrote: > Hi all, > I have just put a couple of new images of the reception of the 3-level > Marco's beacon on my Web site, that show that perhaps the 30-second dot/dash > duration can be shortened. The URL is : http://www.weaksignals.com > > Comments welcome. > > 73, > Alberto I2PHD From crippel at erols.com Sun May 14 22:03:13 2000 From: crippel at erols.com (Chuck Rippel) Date: Thu Jul 3 13:42:02 2003 Subject: [Lf] Interesting Software Message-ID: Here is an interesting piece of software we may be able to use: http://www.brownbear.de/ ================================================== Chuck Rippel, WA4HHG Chesapeake, VA FM16uq Reply to: wa4hhg@amsat.org www Site: http://www.avslvb.com/R390A/index.html ================================================== From akestelo at bellatlantic.net Mon May 15 21:38:39 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] [Fwd: VLF signals on CDs] Message-ID: <3920988F.41B65400@bellatlantic.net> Nan and Sandy Sanders wrote: > Those who have cd and record collections check out > http://www.stormloader.com/gkircher/vlfcd/ > There may be more on the record than the group planed on. > Sandy > > _______________________________________________ > Tacos mailing list > Tacos@amrad.org > http://www.amrad.org/mailman/listinfo/tacos From dibene at usa.net Tue May 16 13:04:22 2000 From: dibene at usa.net (Alberto di Bene) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] Spectran beta 3, build 262 Message-ID: <39211D25.5A303FDE@usa.net> The version beta 3, build 262 of Spectran is now availbale at the URL : http://www.weaksignals.com It is a spectral analysis software, still in beta, expecially tailored for EME and VLF work. Freeware. Alberto I2PHD From akestelo at bellatlantic.net Tue May 16 09:25:54 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] [Fwd: LF: Spectran beta 3, build 262] Message-ID: <39213E52.AC242816@bellatlantic.net> Rik Strobbe wrote: > I tested the lastest version (built 262) last night on Marco's (IK1ODO) > signal. Results are amazing, while I had poor copy with Spectogram I could > get a perfect 'O' signal with Spectran. It just took some time to > experiment with the (many) parameters. > > After some 'playing' with Spectran I found that following parameters gave > best results on the IK1ODO beacon signal : > > Avg Factor = 4 + integration > Sample rate = 8000Hz (or 5512.5Hz) > Contrast = 125 > Res = 0.061Hz (or 0.042Hz at 5512.5Hz sample rate) > Speed = default (startup) value > Lvl = adjusted until the signal is at +/- 75% of the scale at the upper screen > Log = on > > Setting 'Lvl' high enough is very important, from Spectogram I was used to > have a rather low input level for best result but Spectran needs a much > higher input level. Also 'Log' must be active (red). Increasing Contrast > from 100 (default) to 125 improved things a lot. > Marco's signal was too strong to test higher averaging and/or higher Contrast. > > Question to Marco : what was your ERP last night (+/- 22 UT) ? > Would it be possible to decrease it with 3 to 6 dB, to allow to test > Spectran on a really weak signal. > > Finaly : congrats to Alberto and his friend, the lastest version of > Spectran is an excellent tool ! > > 73, Rik ON7YD > > At 12:05 16/05/00 +0200, you wrote: > >The version beta 3, build 262 of Spectran is now availbale at the URL : > > http://www.weaksignals.com > > > >It is a spectral analysis software, still in beta, expecially tailored for > >EME and VLF work. Freeware. > > > >Alberto I2PHD > > > > > > > > From akestelo at bellatlantic.net Tue May 16 21:20:47 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] ... why wait for winter? Message-ID: <3921E5DF.DCD80EFD@bellatlantic.net> MarkusVester@aol.com wrote: > Hello group, > > yesterday night, the qrn seemed to be fairly moderate, so I decided to start > spectrogram at 22:00 UT (5513 Hz, 512 pts, 30 s dwell, 128 averages, > resolution bandwidth with windowing appr. 14 Hz). In the morning, I was quite > surprised to see a fat trace of CFH 137.0 kHz beginning at 00:10. A first > maximum occured around 00:55 with about 11 dBuV/m/14Hz, then the signal dived > down for 15 minutes before it came back with similar strength. After staying > fairly constant for about 1.5 h, it peaked to 13 dBuV/m/14Hz from 02:55 to > 03:10, then decayed and became invisible around 04:10. > > SVX from Greece was strong all night until 02:40, with a pronounced > double-minimum at 03:00 and 03:14 around sunrise. Starting at 23:45, there > was another unidentified narrowband signal with dx-like fading on 136.3 kHz, > up to 10 dBuV/m. The noise between the statics was around -10 dBuV/m/14Hz > during the night, decreasing by 5 dB with daylight. > > For the calculation of signal strength, I have found a ratio of 7 dB between > CFH's observed power density in 14 Hz and its total power, corresponding to > an effective modulation bandwidth of 70 Hz. So the actual field-strength > would be 20 dBuV/m in the maximum. Reducing the noise density to 1 Hz, I > would see -10-11.5 = -21.5 dB/Hz, resultimg in an SNR of 41.5dB/Hz. The ERP > of CFH is said to be around 10 kW, 40 dB above an amateur station's limit. > That would leave us with 1.5 dB SNR in 1 Hz, or 11.5 dB with 10 s dots in 0.1 > Hz, even here in the middle of Europe. In other words: > > Had we tried last night, we would have made it across! > > BTW: Comparable observations in winter and early spring had shown a quite > similar field strength, it was only the time window of common darkness which > was much longer. > > Cheers > Markus, DF6NM From akestelo at bellatlantic.net Wed May 17 08:37:51 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] Voice over IP Message-ID: <3922848F.B3CF62E1@bellatlantic.net> HOUSE BILL BASED ON INTERNET HOAX by Dave Murphy, member@itrain.org For over a year a rumor circulated the net that a Congressman Tony Schnell had sponsored bill, H.B.602P, to impose per-minute access fees on Internet users. Both the congressman and bill number are fictitious. The hoax was accepted prima facie by so many constituents who created such a stir, lawmakers acted. The U.S. House of Representatives passed the Internet Access Charge Prohibition Act on Tuesday. This bill is intended to forestall a problem that doesn't even exist.. "Constituents from across the sixth congressional district wrote and called by the thousands expressing their outrage at such a concept," said Rep. Bob Goodlatte (R-Va.) "Today, the House of Representatives has taken the appropriate step to ensure that such access fees never materialize." The Internet Access Charge Prohibition Act, H.R. 1291, prohibits the Federal Communications Commission from imposing per-minute access fees on Internet users. Calls to ISPs are not subject to such fees. The FCC does not have plans to impose such fees, and called the legislation superfluous. But in a surprising twist, an amendment sponsored by Fred Upton (R-Mich) includes language that leaves the door open to the Federal Communications Commission to levy access charges on VOIP (Voice Over IP) technologies. VOIP supporters are, not surprisingly, upset with Upton's amendment. From akestelo at bellatlantic.net Wed May 17 08:39:53 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:03 2003 Subject: [Lf] - Big & small antennas Message-ID: <39228508.839DDC97@bellatlantic.net> James Moritz wrote: > Dear LF Group, > > This weekend, I am hoping to make another expedition to the > Puckeridge Decca station, which has been made available again > through the good offices of G3JKV and the Crawley club. > > The main motive for this expedition is to do some back-to-back > comparisons between a big antenna (the 100m Decca mast) and a > small, amateur-type antenna (an inverted L about 9m high and 50m > long). The idea is to set the antenna currents so that the same > effective radiated power should be obtained from both antennas, > and then see how signal strengths compare. > > There has been some vigorous debate lately about the advantages > and disadvantages of big and small antennas, with some holding > the view that big antennas have superior radiation patterns to small > ones, and some holding the opposite is true. The aim of the > experiment is to put this to a practical test. We did this before > during the previous trip to Puckeridge, but due to time pressures > and the dreadful weather, relatively little operating was done using > the two antenna setup. The results then were that the two > antennas gave roughly the same results, when transmitter power > was set for same ERP from each antenna (this meant feeding > about 500W into the small antenna, and less than 0.5W into the > main mast!). > > For this weekend, I have put together a tuner/attenuator circuit that > will hopefully allow changing between the antennas with a single > switch, making the comparison much quicker and more direct. I am > hoping this will enable lots more people to take part. The level of > ERP will be very roughly 100mW for both antennas. > > The plan for the weekend is roughly this: > Friday evening - Install gear > Saturday morning - get working, and obtain comparative reports. > Later on Saturday - run station at 1W ERP from main antenna > Sunday - open to suggestions; I have notified RA in case anyone > would like to try 73kHz QSO's. > Sunday afternoon - pack up and go home. > > Due to this being a small-scale expedition, I will probably stick to > normal CW, but might be prevailed upon to drag my PC across a > field if people are really keen to hear some QRSS....... > > Of course, nothing ever goes entirely according to plan, but it > should be fun. Any QSO's, listener reports or measurements would > be welcome. If you have any suggestions, please let me know. > > Cheers, Jim Moritz > 73 de M0BMU From akestelo at bellatlantic.net Thu May 18 22:48:33 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:04 2003 Subject: [Lf] [Fwd: LF: Puckeridge Experiments] Message-ID: <39249D70.FF2415AE@bellatlantic.net> James Moritz wrote: > Dear LF Group, > Glad to see my intended experiments are generating some > interest. At the moment, my main priority is to get everything up to > Puckeridge in working order, which is quite an effort, but here are > some further details of what I hope to do, and the point of doing it: > > The inverted L antenna will be located 130m from the main mast, > off the main ground system and with it's own ground spikes. The > coax feeder will run to the base of the mast, but will be decoupled > using a common-mode choke. The main antenna will be grounded > while the inverted L is transmitting. This should ensure the two > antennas have the least coupling possible whilst still being on the > same site. It will be possible to monitor RF current flowing in the > main mast while transmitting from the small antenna, so that the > degree of coupling can be assesed. It should be possible also to > try the main antenna 'floating', or resonated. > > ERP will be calculated on the basis of estimated radiation > resistance and measured antenna current for each antenna. For > the inv. L this should be about 20 milliohms and 2A, for the main > mast about 0.7 ohms and 0.34A, both giving about 80mW radiated > power in theory. Final adjustments will be done based on the actual > current that can be achieved on the day into the small antenna. > > By definition, two transmitters/antennas giving the same ERP will > yield the same signal strengths at equal distances. But a number of > things may modify the actual ERP obtained, in comparison with the > calculated figure: > i) The effects of the environment around the antenna - eg. houses, > trees, could absorb some of the radiated signal - is not taken into > account in simple calculations of ERP. > ii) Different sizes of antennas may have different radiation patterns > - some have suggested that small antennas have predominantly > high angle radiation, which does not propagate usefully for DX > communication. Theory says that this should not be a significant > factor unless the antenna is a large percentage of a wavelength > high, which even 100m isn't, at 136kHz. > iii)There are also other factors that may play a part, such as > penetration of the EM field into the ground, and radiation of > horizontaly polarised signals, which may affect field strength at a > distance. > > Having a large commercial antenna and a small amateur antenna > at the same location, in the same environment, gives a simple way > of testing whether the theory as applied to large, commercial > antennas is also valid for the 'wet string' antennas that amateurs > have to use. This is important both from the regulatory viewpoint > (are you exceeding the 1W limit?) and the communications > viewpoint (just how much signal are you putting out?). > Measurements by myself and others suggest that most of the time, > signal strengths are down on what would be expected from theory. > > Equipment details: > TX: 0-350W, VFO + Mosfet PA > RX: Homebrew superhet > Creaking 386 laptop for beacon and QRSS keying - no receive > software. > 2 Tuners - 1 with motorised tuning for remote control of small > antenna, one with power attenuator for main antenna. > Sundry test gear for setting up and checking purposes - frequency > counter, selective voltmeter, RF ammeters etc. > 1.5kW Generator > > Since it is a one-man effort, I expect to have my hands full, and am > not sure what it will be possible to accomplish. However, the main > thing will be to get plenty of comparative reports. Field strength > measurements would also be very useful. I hope to also put out > some beacon signals, probably during Saturday evening, with 3 > configurations, ie. inv. L antenna, 80mW ERP, main antenna, > 80mW ERP, main antenna 1W ERP, perhaps around 137.2 - > 137.3 kHz. I can't leave it on all night, mainly because the > generator will have to be re-fuelled, but I'll do what I can - let me > know if you have better ideas! > > Cheers, Jim Moritz > 73 de M0BMU From akestelo at bellatlantic.net Fri May 19 00:04:34 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:04 2003 Subject: [Lf] [Fwd: LF: News from Canada on 136KHz] Message-ID: <3924AF41.A1DC75EE@bellatlantic.net> Dave Goodwin VE2ZP/VE9CB wrote: > Canada is edging closer to a VLF Amateur allocation. > > To understand this bulletin, you should know that CARAB is the Canadian > Amateur Radio Advisory Board, composed of employees of the Canadian radio > regulatory agency (Industy Canada) and the national organisation > representing hams, the Radio Amateurs of Canada. > > RAC Bulletin 00-048E Semi Annual CARAB meeting in Ottawa > > >From: RAC Headquarters > > > >Date: May 18, 2000 > > > >Subject: Semi Annual CARAB meeting in Ottawa. > > > >On April 27, 2000, RAC President Ken Oelke, VE6AFO Co-Chaired > >the 14th Meeting of CARAB. In attendance were First Vice > >President Ralph Webb, VE7OM, Vice President of Government and > >International Affairs Ken Pulfer, VE3PU, Atlantic Director > >William Gillis, VE1WG, Quebec Director Daniel Lamoureux, > >VE2KA and Jim Dean, VE3IQ. Officials in attendance from > >Industry Canada were Darius Breau, Manager, Operational > >Policies, Radiocommunications and Broadcasting Regulatory > >Branch, Tom Jones, Chief, Authorization and Harold > >Carmichael, Program Manager, Certificates and Examinations, > >Quebec Region. > > > >The following were hightlights of the meeting. > > > > >- RAC's request for a . . . VLF > >allocation on 135.7 to 137.8 kHz, is still under review by > >Industry Canada. > > From akestelo at bellatlantic.net Fri May 19 09:20:12 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:04 2003 Subject: [Lf] ERP and ERP Message-ID: <3925317C.2B19931D@bellatlantic.net> WarmSpgs@aol.com wrote: > In a message dated 5/18/00 8:52:58 AM Eastern Daylight Time, > j.r.moritz@herts.ac.uk writes: > > << ERP will be calculated on the basis of estimated radiation > resistance and measured antenna current for each antenna. For > the inv. L this should be about 20 milliohms and 2A, for the main > mast about 0.7 ohms and 0.34A, both giving about 80mW radiated > power in theory. > > By definition, two transmitters/antennas giving the same ERP will > yield the same signal strengths at equal distances. But a number of > things may modify the actual ERP obtained ... >> > > Please don't misunderstand my earlier inquiry, Jim. I think this experiment > is worthwhile and may yield much useful experience. I'm just concerned about > the seemingly rather casual use of the term ERP, and the tendency to equate > it with power dispersed in radiation resistance. These are very different > things. > > ERP _is_ actual ERP, and can only be actual ERP. That is, ERP is determined > by actual field strength. It therefore already includes antenna and nearby > environmental losses; hence, equal field strength is the only way to actually > say the ERP of two systems are equal, not the power in the radiation > resistance. (Measuring the signal out of two different systems with equal > powers in the radiation resistance is instructive, of course, because it does > permit one to compare the interaction of two different radiators with their > environments. I take this to be your fundamental objective.) > > Someonce commented earlier--I was thinking it was Rik, although I can't find > the post now--that there were those who believe that one watt ERP from one > kind of antenna is better than one watt ERP from another kind. I got a good > chuckle from that, but actually there is a certain grain of truth to the > concept...particularly when the radio authorities set a maximum ERP limit on > transmissions. > > This means that the field strength in ANY direction or elevation cannot > exceed so many mv/m at so many km from the antenna. (Different > administrations may choose to define the distance differently for their own > regulatory purposes, and the corresponding field strength will vary inversely > with that part of the definition.) The key words in the definition of > maximum ERP, though, are usually "maximum field" in "any direction" from the > antenna. I supervise a number of FM broadcast stations, by way of showing > why this is significant. One has a maximum ERP of 100kw, yet covers less > than half the geographical area of another one that also has a maximum ERP of > 100kw, over similar terrain. Why? Because the former uses a directional > antenna. The _maximum_ ERP is indeed 100kw in the main lobe, but is less in > all other directions around the antenna than its omnidirectional counterpart. > > If any two given antennas have the same 1w ERP in the same direction, and it > happens to be the direction you need to reach, then all is well. You have > equal field strength...in that one direction. But, if that maximum 1w ERP > happens to be in a less useful direction from one antenna (say, straight up) > than the other, then yes, 1w ERP produced by one antenna can be different > from 1w ERP produced by another! > > Neither any theory nor practice that I can find indicates two electrically > short verticals (one roughly .004 wavelength and the other .04 wavelength, > for instance) would produce any different radiation pattern. If you can > force enough power through them to achieve the same ERP, it will be achieved > in all directions, barring local obstructions. > > Your experiment, however, is not so much about big versus small, but between > antennas of differing shapes. That's what I think is interesting: can > amateurs make up for terrible inefficiency by directing their energy with > other geometries? And if so, can it be done predictably, or will we always > be imprisoned by trial and error? I'll be watching with keen interest. Good > luck. > > 73, > John KD4IDY From akestelo at bellatlantic.net Sat May 20 10:21:33 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:04 2003 Subject: [Lf] More on Red X Corona Dope Message-ID: <3926915C.B325FDC@bellatlantic.net> les@highnoonfilm.com wrote: > Lyle responded to my earlier question about if this stuff could > actually improve the "Q" of a coil as stated in the QST article. > I thought his comments were worth sharing... > ---------------------------------------------------------------------------- > ----------- > > It's a little hard to believe that there is anything you can spray on a > coil that will actually *improve* the Q. Hard to beat air as an > insulator. I would expect the Q, as measured with a Boonton type of Q > meter, to *decrease* a tiny bit because the added dielectric between the > windings will cause a slight increase in distributed capacitance. > However, the coil dope should help to keep the Q from going to pot > because of moisture, insulation degradation, etc, so all in all it > sounds like a good idea. > > My present coil is wound with enamel insulated Litz wire, and even > though it is protected by the upside-down 5 gallon plastic bucket, it > seems to take several dry days after a very wet period for the antenna > current to recover fully. This could be due to moisture in any number of > things like nearby trees and the antenna support ropes, but I don't > remember it being that much of a problem with my old basket-wound coil. > By the way, when I first put up the #14 basket-wound coil, I covered it > with a plastic bag, which blew to shreds in the first wind storm. After > that, the coil hung out there in the weather for more than 5 years > before it was replaced with the Litz coil. I did spray the Litz coil > with some Krylon to stabilize the floppy windings, but the can was > almost empty, it was probably the last warm day in fall, and I didn't > feel like running to town for a new can of spray. Maybe it would be > worth hitting the coil with some of that Red X spray before the next > LowFER season. > > _______________________________________________________________ > > My own thought is that the dope might actually help to improve the > dielectric properties of lossy insulators such as PVC that are > often used as coil forms. Especially if they were carefully coated > by hand using the "brush" type dope. Allowing each coat to try > and building up a thick coating. > > Then after construction, as Lyle suggested, it would be worth > coating the actual coil itself, if just to reduce moisture problems, > such as "de-tuning". And to extend the life of the coil. > > Back to the PVC problem. I've heard it suggested that using > a sabre saw to cut away as much of the PVC from the coil > form as possible can improve "Q" (By exposing as much of > the coil as possible to an "air" insulator rather than PVC. > > Has anyone tested this? How much of an improvement could > this yield? > > Les Rayburn, KT4OZ > (XMGR) > > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From akestelo at bellatlantic.net Sat May 20 17:45:05 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:05 2003 Subject: [Lf] use of Liaison Message-ID: <3926F951.ECEBD9B3@bellatlantic.net> Peter Dodd wrote: > On the 10th of March I received an e-mail from Alan Melia saying that > Brian Rogerson, CT1DRP, was in a position to receive 73kHz signals; > although all he had heard to that date was Rugby. Brian was keen to > try to receive amateur signals on this band before it was withdrawn > (due for the end of June 2000 at the time). > > After an initial exchange of e-mails I agreed to transmit QRSS > signals on 71.8kHz but the results were negative. > > I then asked Brian to send me a .JPG of his Spectrogram screen. The > display was a mess with masses of electrical QRM. > > In a series of e-mail exchanges I passed to Brian the collective LF > group wisdom (G4GVC et al) for improving the receive system. This > included improving the antenna resonating and matching and extending > the ground system. The e-mails received from Brian showed intelligent > response to the advice and the .JPG images continuing improvement in results. > > On the 5th of April I received an e-mail from Brian, with an attached > .JPG, saying "was this you". > It certainly was, although only readability 'T'; more recognizable > from the frequency characteristics on keying than the data! > > On the 10th of April I received a further .JPG from Brian showing my > the 72kHz side of my cross-band QSO with I5TGC, this time readability 'O'. > > The reason for describing this saga in detail is to show the value of > liaison for propagating LF experience, particularly if you are > trying to achieve a long distance contact over over a path whose > characteristics are not well known. When you realise that Brian had > not received any amateur signal until the 5th of April, to receive a > 30mW signal over 1200km as his first received amateur signal was > quite an achievement. > > Could not such a similar procedure be used for the transatlantic path? > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Sat May 20 23:18:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:06 2003 Subject: [Lf] Different types of antennae] Message-ID: <3927478C.F5C6F0E5@bellatlantic.net> Cantrell Bill-QA0057 wrote: > Tim, > On a mobile BPSK reception experiment through Arkansas, I noticed that very > tall trees along the median of the Interstate Hiway would attenuate > weak-signal LF reception, even though the trees were ~40 to 50 feet away > from the roadway, but they were also ~50 to 80 feet tall] This made the > difference between E-field probe reception (using BPSK GRAB) and no signal. > That is, I could receive the signal only if there were none of these trees > in the median. So if you can get MORE THAN 100 feet away from trees that > are 100 feet tall, then that may be good enough. (I am assuming that the > effect of trees on reception would be reciprocal to transmission.) > > Regards, > Bill > "TEXAS" & WD5CVG > > -----Original Message----- > From: Tim Pauly [mailto:tpauly@twcny.rr.com] > Sent: Saturday, May 20, 2000 2:27 PM > To: lowfer@qth.net > Subject: Re: [Lowfer] Different types of antennae > > On Sat, 20 May 2000 14:10:24 -0500, Lyle Koehler wrote: > > >hat on your 40-foot tower and feed it the way Bruce, W0BK does for his > >BK beacon. In the winter the trees freeze and become fairly good > >insulators. More details on my web page at > >http://www.computerpro.com/~lyle under "Listening for LowFERs, Part 2" > >and the description of the BEAMHAT.ANT models under "Computer Modeling > > How 'close' to trees is too close? I could put a ground mounted vertical in > the front of the house which would be open > from trees for at least 80-100 feet in 3 directions. But it is also at the > base of the hill, and the top of the antenna would be > at house level (about 15 feet from the house). You'd have to see the way > this crazy place is laid out to know what I > mean. Our house is literally situated on the side of a very steep valley. > The house itself is about 40 feet above street > level (lots of steps to carry groceries up!). My tower is about 50-60 feet > behind the house, but the base of it is above the > second floor level (like I said, we're on the side of a very steep valley!) > Also, my tower is grounded and mounted with > threaded rod set in concrete. Unless I made a "folded unipole" out of it ;-) > I don't think it would work well. There is also > VHF transmit antenna already mounted on it, and a UHF relay antenna will be > going on it soon... > > Tim > > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net -------------- next part -------------- An embedded message was scrubbed... From: Cantrell Bill-QA0057 Subject: RE: [Lowfer] Different types of antennae Date: Sat, 20 May 2000 18:50:37 -0500 Size: 4167 Url: http://atanasoff.rf.org/pipermail/lf/attachments/20000520/64ef352d/attachment.txt From akestelo at bellatlantic.net Sun May 21 08:57:10 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:06 2003 Subject: [Lf] Best tone for aural copy] Message-ID: <3927CF16.20287E3F@bellatlantic.net> Dick Rollema wrote: > To All from PA0SE > > In an e-mail to Bob, ZL2CA. discussing the PA0LQ audio filters, I mentioned > a thesis > on the reading of morse code signals in noise. > As a result Bob asked: > > > Do you know a way of accessing the university and thesis details? > > > I gave the following reply which I also sent to the reflector because > others > may be interested in it. > > Bob, > > The thesis has the title "Signal detection in noise, with special reference > to telegraphy". > > The author is Peter Montn?mery, SM7CMY, who is employed at the Department > of Otorhinolaryngology [say that fast ten times :-)], Head and Neck > Surgery, University Hospital, Lund, Sweden. Code number is > ISRN LUMEDW/MERL -- 1038--SE. > > Some of the subjects treated are: > > 1. Recognition of telegraphy disturbed by noise at different S/N-ratios and > different telegraphy speeds. > > 2. Recognition of telegraphy signs at different listening levels and > frequencies. > > 3. Effect of dichotic presentation on the recognition of telegraphy > signals. > > 4. Recognition of telegraphy in hearing-impaired telegraph operators. > > 5. Performance of electronic morse decoders in decoding telegraphy masked > by > noise. > > 6. Detection of trains of tone pulses masked by noise. > > I learned about the thesis by a message from Peter Schnoor, DF2FL, via the > LF-Group reflector, considerable time ago. > > Via a friend at the Leyden University I managed to obtain a copy which took > many months to arrive. > After writing an article about it for our VERON magazine "Electron" (still > waiting to appear) I have passed it on to my good friend PA0CX/F2ZI who > will > or already has sent it to Pat Hawker, G3VA. > > > As a further aside, do you know why Harry picked 1000 Hz for his filter? > > I don't know. > > For my filter I had to use 1000Hz because my German LF-receiver of the > sixties has a fixed BFO that produces an audio note of 1000Hz when the > signal is centred in the IF filters. > > But when I am busy in my shack doing other jobs I often leave the receiver > on with a wide IF-filter selected, no audiofilter and such high volume > that the headphones function as speaker. > I have noted several times that I could detect a weak signal this way. > After putting on the headphones and switching on the 30Hz audio filter it > was often very difficult to read the signal! It again goes to show that > the ear-brain combination acts as tracking bandpass filter that should not > be "assisted" by too much pre-filtering. > > 73, Dick, PA0SE From akestelo at bellatlantic.net Sun May 21 09:01:54 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:06 2003 Subject: [Lf] Different types of antennae] Message-ID: <3927D032.C7532784@bellatlantic.net> Lyle Koehler wrote: > Michael Mideke published the results of a terrain experiment a number of > years ago. His experiment compared transmitting results with 3 antennas, > each consisting of a 32 to 36 foot vertical with a substantial top hat, > and with identical currents at the antenna bases. Site 1 was wooded and > in a valley, Site 2 was mostly brushy with scattered oak and pine trees, > on a small plateau halfway up a hill, and Site 3 was surrounded by brush > ranging in height from 2 to 8 feet but on the top of a hill. Mike's > brief article doesn't give the elevation differences between the three > sites but I would guess that it was in pretty mountainous terrain. > Relative ground wave signal levels at distances of 25 or more miles were > 0 dB for Site 1, +12 dB for site 2, and +20 dB for Site 3. Site 1 was > never heard at more than 50 miles; best DX for Site 2 was 220 miles, and > Site 3 was copied at 2000+ miles (apparently this was California LowFER > beacon "Z2", heard in Hawaii). > > As for feeding a grounded tower; BK's tower *is* grounded and has an HF > triband beam and a 2m vertical on top as described on my web site. The > hard part is isolating the ham antennas *and* their coax feeds from the > grounded tower. > > -- > Lyle, K0LR > > http://www.computerpro.com/~lyle > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From akestelo at bellatlantic.net Sun May 21 22:44:37 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:06 2003 Subject: [Lf] Different types of antennae] Message-ID: <39289104.520028C4@bellatlantic.net> Pierre Thomson wrote: > Hi Jim, > > While your logic is good in the case of a quarter wave vertical (with > 1/100 wavelength metal trees around it), the picture is quite different > when the radiator is an "infinitesimal monopole" such as the average > Lowfer installation. Here the antenna and ground system act as a > big capacitor, and the bit of radiation that does get out results from > the current on the vertical conductor between the plates. Any poor > dielectric (and moist trees are pretty bad) close to the capacitor > will degrade the Q to some extent. This is why trees closer than > about 100 feet are bad. And resistive trees are actually WORSE > than metal in this respect. > > Another factor is that the E-field around such an antenna is primarily > vertically polarized, and any vertical conductors nearby will absorb > a portion of the energy. This also applies to reception; you can notice > the effect with your car radio tuned to a distant AM station. It fades > noticeably when you drive through dense forest, as compared to open > fields. > > Based on a few years of LF work and a few decades of HF, I would > contend that trees have more effect on Lowfer transmitting antennas > than, say, on horizontal dipoles. The latter can be strung through a > tree with great results; a Lowfer antenna suspended in a tree is > doomed from the start. > > Just my observations... > > 73 Pierre Thomson KA2QPG / RI > > > -----Original Message----- > > From: WB9UWA Jim Shaffer [SMTP:wb9uwa@gte.net] > > Sent: Sunday, May 21, 2000 7:59 PM > > To: Pierre Thomson > > Subject: Re: [Lowfer] Different types of antennae > > > > Has anyone modeled trees on antenna software on these frequencies? > > It would seem to me that if you model the trees in a worst case > > conditions (no resistance) then you have metal poles near by that > > are a very very very very very small fraction of a quarter wavelength > > high working against ground. These near by metal poles as such > > should have very little effect on an antenna that would be over a 1000 > > foot tall if it were a quarter wave length. When these metal trees are > > modeled, the effect should be to modify the pattern of the LF > > antenna. Of course a real tree might absorb the signal rather > > then reflect it. Hams have been stringing wire antennas in and around > > trees for years with good results. Certainly the effect on the signal is > > going to be greater on HF then on LF. > > > > It would be my guess that this study shows more the effect of signal > > blockage by land then by trees although I have not seen the study first > > hand. > ... > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From lemaster at pressroom.com Mon May 22 08:10:10 2000 From: lemaster at pressroom.com (George Lemaster) Date: Thu Jul 3 13:42:07 2003 Subject: [Lf] AMRAD final call for papers Message-ID: <00e101bfc3de$4c697940$1f9508d1@anyone> FINAL CALL FOR PAPERS AMRAD Technical Symposium June 17, 2000 The Quality Inn Governor 6650 Arlington Boulevard (Near 7 Corners) Falls Church, Virginia 22042 Papers are sought for the all-day, June 17, 2000 AMRAD Technical Symposium on current, future, and retrospective Amateur Radio and telecommunications technology. Subjects of interest include: a.. Low frequencies (transmitting, receiving, lessons from experiments) b.. Digital signal processing/software defined radios c.. Multimedia (convergence of digital voice, image, data) d.. Packet radio/higher speeds/Internet connection e.. Spread spectrum (where do we go with the new FCC Rules?) f.. Small amateur satellites (AMRAD-OSCAR-27 and beyond) g.. Amateur Packet Reporting System (APRS) h.. Telecommunications for the disabled i.. Microwaves and millimeter waves (terrestrial/satellite) Paper deadline: May 27, 2000 in Microsoft Word or WordPerfect to lemaster@pressroom.com. Proceedings will be published. For information please contact: George Lemaster, WB5OYP lemaster@pressroom.com or Paul Rinaldo, W4RI w4ri@amrad.org -------------- next part -------------- An HTML attachment was scrubbed... URL: http://atanasoff.rf.org/pipermail/lf/attachments/20000522/bd2bcd4d/attachment.html From akestelo at bellatlantic.net Mon May 22 22:09:30 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:07 2003 Subject: [Lf] Lightning map of the US Message-ID: <3929DA4A.2641C90E@bellatlantic.net> Lyle Koehler wrote: > Want to know where all that QRN is coming from? Go to > http://www.lightningstorm.com/lightningstorm/gpg/lex1/mapdisplay_free.jsp > -- > Lyle, K0LR > > http://www.computerpro.com/~lyle > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From fgentges at mindspring.com Tue May 23 01:13:15 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:07 2003 Subject: [Lf] Complex Impedance Analyzer Message-ID: <392A055B.C9774CF0@mindspring.com> Hi, While at Dayton I stopped by the booth and talked to the technical gurus that make the CIA box we have used from time to time. They said the HF version would go down to 100 kHz with limited errors as is. They modified a few to improve the small residual errors but do not like to do that because it introduces larger errors at the top end at 50 mHz. We had observed that at 136 kHz the 1 kHz steps were a bit course and we needed .1 kHz steps to resolve the antenna tuning. They have a newer version with more bells and whistles (and more money) but it tuned .1 kHz steps. They picked it up and demonstrated that. They called it the "VIA" rather than the "CIA". Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From lemaster at pressroom.com Tue May 23 05:38:41 2000 From: lemaster at pressroom.com (George Lemaster) Date: Thu Jul 3 13:42:07 2003 Subject: [Lf] AMRAD Technical Symposium Message-ID: <016601bfc492$4d04e920$655008d1@anyone> I'm sure most of you are aware of the upcoming AMRAD Technical Symposium and 25th Anniversary Dinner on June 17. Full information will be posted on the AMRAD website www.amrad.org. Just to get an initial attendance count, please reply to lemaster@pressroom.com if you plan to attend. Please do not reply to tacos or lf reflector. Thanks. George Lemaster WB5OYP The AMRAD Technical Symposium will be held Saturday, June 17th. 8:30 - 5:00 The Technical Sessions will be in the Governor Room at: The Quality Inn Governor, 6650 Arlington Boulevard, Falls Church, Virginia, 22042 (about 6 mi. west of DC on Rt.50) The AMRAD 25th Anniversary Dinner will be held at 6 PM, Saturday, June 17 at McGuil's Cafe, 6633 Arlington Blvd (across the street from the technical symposium). The main speaker will be Dale Hatfield, W0IFO, Chief, Office of Engineering and Technology, FCC. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://atanasoff.rf.org/pipermail/lf/attachments/20000523/da2ce28c/attachment.html From akestelo at bellatlantic.net Wed May 24 09:08:51 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:08 2003 Subject: [Lf] Excellent free DSP Book] Message-ID: <392BC653.D724B69C@bellatlantic.net> Talbot Andrew wrote: > For a very good book on DSP look at WWW.DSPGUIDE.COM > Title "The Scientist and Engineer's Guide to Digital Signal Processing" > by Steven W Smith > > To quote from the preface : > > "This book was written for Scientists and Engineers........ The goal is > to present practical techniques while avoiding the barriers of detailed > mathematics and abstract theory" > > Just what I like, and based the few bits I've read so far appears to be > true. Charles, G4GUO, described it as the best intro book for DSP he > had ever seen. > > Unusually, it can be downloaded FREE in .PDF format, as well as > purchased online for $64 plus P&P. Each chapter (35 files in total) is > a separate file and has to be downloaded one at a time. I suggest > downloading and reading FRONTMAT.PDF first which contains the index, and > means you only need to download interesting chapters as and when. > > I intensely dislike reading from the computer screen, printing out each > page on a Laserprinter costs considerably more than buying the book and > takes ages from Acrobat reader, so an order has been sent............ > > Andy G4JNT From akestelo at bellatlantic.net Thu May 25 08:18:14 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:08 2003 Subject: [Lf] [Fwd: LF: DDS Board - Anyone interested ?] Message-ID: <392D0BF6.5A91BF6@bellatlantic.net> Talbot Andrew wrote: > I am considering bulk manufacture of a Printed Circuit Board for the > AD9850 DDS chip. The design has already been tested and includes the > DDS, output filter, voltage regulator and a 16F84 PIC. Resident > software allows the DDS source to be controlled over an RS232 link from > a PC with ASCII commands. This allows for control from a simple > terminal programme as well as custom software for PSK/ FSK etc. There > is no reason why different PIC software can't be used for keyboard / > rotary encoder etc. Mostly surface mount (large 1206 components > though) but conventional PIC in a socket for easy firmware changes. > > If there is enough interest I will go ahead with a PCB order. It is > possible a company (see WWW.HF-INST.CO.UK ) may take the design on > board and market as a complete signal source, but for now I will just > get PCBs made if enough interest is shown. Not sure of the price, it > depends on such things as quantity, how many plated through holes, > delivery timescales and probably the phase of the Moon ! > > The DDS can be clocked with any frequency source desired. For LF I use > a 5MHz input derived from a master reference which allows outputs up to > 1.7 MHz with 0.001 Hz resolution, but any clock up to 120MHz (40 MHz > maximum output) is useable. > > Anyone interested, please let me know so I can get an idea of whether it > is worth going ahead with a commercial run. > > Andy G4JNT > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From kayser at sympatico.ca Thu May 25 09:38:27 2000 From: kayser at sympatico.ca (Larry Kayser) Date: Thu Jul 3 13:42:08 2003 Subject: [Lf] DDS board availability Message-ID: <000501bfc646$248bb810$0a00a8c0@server1.ThreeLakes.ca> Finally, maybe a DDS board available soon. Andy, G4JNT is considering producing a PC board that has a PIC controller IC controlling one of the Analog Devices AD9850 chips. This gives one a DDS of the highest quality. The Reference oscillator can be anything available, from atomic standards to simple reasonable quality oscillator modules up to 100 MHz or so. The OUTPUT from the DDS is up to 1/2 of the reference frequency, a 5 MHz oscillator will allow steps as small as a few milliHz from a few kHz to 2500 kHz. These devices are excellent for making LF transmitters that can easily do FSK, PSK etc. They can also be used as Local Oscillators and BFO's for a super stable receiver as well. If you might be interested read Andy's email that follows and you can email to Andy at Talbot Andrew and let him know. PLEASE REMEMBER EMAIL ANDY AND NOT ME HI......... I am considering bulk manufacture of a Printed Circuit Board for the AD9850 DDS chip. The design has already been tested and includes the DDS, output filter, voltage regulator and a 16F84 PIC. Resident software allows the DDS source to be controlled over an RS232 link from a PC with ASCII commands. This allows for control from a simple terminal programme as well as custom software for PSK/ FSK etc. There is no reason why different PIC software can't be used for keyboard / rotary encoder etc. Mostly surface mount (large 1206 components though) but conventional PIC in a socket for easy firmware changes. If there is enough interest I will go ahead with a PCB order. It is possible a company (see WWW.HF-INST.CO.UK ) may take the design on board and market as a complete signal source, but for now I will just get PCBs made if enough interest is shown. Not sure of the price, it depends on such things as quantity, how many plated through holes, delivery timescales and probably the phase of the Moon ! The DDS can be clocked with any frequency source desired. For LF I use a 5MHz input derived from a master reference which allows outputs up to 1.7 MHz with 0.001 Hz resolution, but any clock up to 120MHz (40 MHz maximum output) is useable. Anyone interested, please let me know so I can get an idea of whether it is worth going ahead with a commercial run. Andy G4JNT From akestelo at bellatlantic.net Fri May 26 10:59:29 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:08 2003 Subject: [Lf] LF: Diversity reception] Message-ID: <392E8341.59D53BA3@bellatlantic.net> Tom Boucher wrote: > Mike, Alan, Larry and all, > > Surely the AR88s would be used with an external combiner? I would guess > that the D suffix probably indicates the receivers had the necessary > interface to an external combiner. Todays aerospace telemetry systems > employ space, frequency and polarisation diversity, sometimes > simultaneously which involves banks of receivers and combiners. > > Space diversity, using two physically seperate receive antennas, is used > to overcome signal fades due to multi-path phase cancellation. Frequency > diversity uses two seperate RF links on different frequencies to > overcome radiation pattern nulls on larger vehicles. Polarisation > diversity is used to overcome polarisation twisting of the received > signal due to vehicle rolling or other factors. > > A fourth system is time diversity where the data is delayed and > transmitted again to overcome short term signal attenuation such as on > re-entry vehicles. > > Multiple receivers are necessary with a combiner which takes each > receiver output and sums it in an optimal ratio depending on the S/N > from each. > > A better system, known as Pre-Detection Combining, phase locks the two > IF signals together and combines at IF frequency. > > Maximum theoretical improvement with two similar signals is 3dB but of > course if one signal has a good S/N and the other is lousy, then the > improvement can be much greater. Could be worth exploring some of these > techniques for scraping LF signals out of the noise. > > Larry did you say you junked an AR88? What a terrible admission! I'm > sure someone could have put it to good use, if only at the end of a long > chain by a yachtsman. > > 73, Tom G3OLB. From tfox at erols.com Fri May 26 19:35:38 2000 From: tfox at erols.com (Terry Fox) Date: Thu Jul 3 13:42:08 2003 Subject: [Lf] Re: [Fwd: LF: DDS Board - Anyone interested ?] References: <392D0BF6.5A91BF6@bellatlantic.net> Message-ID: <392EFC3A.56A64872@erols.com> There are already a couple boards out there using the 9850. I think there was one in QEX a couple years ago, complete with software. It used a 9850, PIC, shaft encoder, etc., and looked a lot like the kit from the guy in Gaithursburg, MD. I'm not suggesting another design wouldn't be a good idea, and am all for more experimentation. Terry Andre' Kesteloot wrote: > Talbot Andrew wrote: > > > I am considering bulk manufacture of a Printed Circuit Board for the > > AD9850 DDS chip. The design has already been tested and includes the > > DDS, output filter, voltage regulator and a 16F84 PIC. Resident > > software allows the DDS source to be controlled over an RS232 link from > > a PC with ASCII commands. This allows for control from a simple > > terminal programme as well as custom software for PSK/ FSK etc. There > > is no reason why different PIC software can't be used for keyboard / > > rotary encoder etc. Mostly surface mount (large 1206 components > > though) but conventional PIC in a socket for easy firmware changes. > > > > If there is enough interest I will go ahead with a PCB order. It is > > possible a company (see WWW.HF-INST.CO.UK ) may take the design on > > board and market as a complete signal source, but for now I will just > > get PCBs made if enough interest is shown. Not sure of the price, it > > depends on such things as quantity, how many plated through holes, > > delivery timescales and probably the phase of the Moon ! > > > > The DDS can be clocked with any frequency source desired. For LF I use > > a 5MHz input derived from a master reference which allows outputs up to > > 1.7 MHz with 0.001 Hz resolution, but any clock up to 120MHz (40 MHz > > maximum output) is useable. > > > > Anyone interested, please let me know so I can get an idea of whether it > > is worth going ahead with a commercial run. > > > > Andy G4JNT > > > > -- > > The Information contained in this E-Mail and any subsequent correspondence > > is private and is intended solely for the intended recipient(s). > > For those other than the recipient any disclosure, copying, distribution, > > or any action taken or omitted to be taken in reliance on such information is > > prohibited and may be unlawful. > > _______________________________________________ > Tacos mailing list > Tacos@amrad.org > http://www.amrad.org/mailman/listinfo/tacos From akestelo at bellatlantic.net Sat May 27 09:10:41 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:09 2003 Subject: [Lf] LORAN sidebands] Message-ID: <392FBB41.27667666@bellatlantic.net> Walter Blanchard wrote: > At 04:18 25/05/00 +0100, you wrote: > >Can anyone provide a formula or graph showing the relative strength of > >sidebands down to 80 kHz, please? > >73 de John Rabson G3PAI > > John, > Official US Loran-C spec. states : > "Specification for energy distribution outside the 90-110 kHz band will be > achieved > if the spectral density of the radiated signal at 90 kHz and 110 kHz is > down at least 20 dB relative to its value at 100 kHz" > "Total spectral energy below and above the 90-110 kHz band shall be less > than 0.5% each". > It is specified this way because the designers are only interested in > shaping the rising > edge of the pulse properly and don't much care how it decays. So the > spectrum > differs between transmitters and is not necessarily a smooth exponential decay. > That's why we have trouble at 136 kHz. > Walter G3JKV. From akestelo at bellatlantic.net Sat May 27 23:22:48 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:09 2003 Subject: [Lf] comments Big and Small Antennas at Puckeridge] Message-ID: <393082F8.415D569E@bellatlantic.net> vernall wrote: > To all reflector readers: > > Thanks to James M0BMU for carrying out the practical experiments at > Puckeridge and writing a report on the results. Well done. > > Consideration of why the "small" antenna was better by some 4 dB (using > the normalised information) is a challenge. It may be speculation, but > a suggestion is that the effective height of the "small" antenna may > have been more than the physical height. Noting from the report: > > > .... a small, amateur-style inverted 'L' antenna. > > > > The vertical part of the L was 9m high and about 130m to the south of > > the main mast. The single 24/0.2 top wire (about 1mm diameter) ran > > directly away from the main mast, and was 42m long. The whole of the > > small antenna was off the main ground system, which extended over a > > circular area for about 120m from the base of the mast. The small > > antenna ground system had 4 ground rods, 1m long, spaced a couple of > > meters around the antenna tuner. The fencing wires that ran under the > > antenna, about 50m long, were also bonded to the small antenna ground, > > and were not connected to any other fences. > > The ground system of the "big" antenna would have many long radials and > establishes "reference RF ground" for the wider environment. If I read > the report correctly, the "ground" from the small antenna was separate, > and at LF the skin depth in soil can be many metres, so there exists a > possibility that the small antenna system has a greater effective height > (relative to the big antenna ground) than physical height (9 m). > Radiation resistance is a function of effective height squared, so only > a few "extra metres" would be worth a few dB. As the radiation > resistance figure used in the experiment was estimated on physical > height, then it could have a lower value than actual and possibly > explain some of the observed discrepancy? > > Testing the small antenna in a "backyard" may have some reverse issues > for effective height, where houses, sheds and trees raise the height of > the ground plane. Testing on a genuinely clear site would give less > uncertainty to an experiment. > > 73, Bob ZL2CA From akestelo at bellatlantic.net Sat May 27 23:22:00 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:09 2003 Subject: [Lf] Big and Small Antennas at Puckeridge] Message-ID: <393082C8.F8F282A2@bellatlantic.net> James Moritz wrote: > Dear LF Group, > > Here is the report on the "Big and Small" antenna experiments I did at Puckeridge last weekend, and which several subscribers to the reflector contributed signal reports to. Briefly, it appears that the small antenna was more efficient than was predicted from theory. Any constructive comments would be welcome. > > Cheers, Jim Moritz > 73 de M0BMU > > _______________________________________________ > Big and Small Antenna Experiments at Puckeridge Decca Site > > The main objective of the experiments was to compare the received signals from two very different antennas, each radiating the same power, as calculated with the usual techniques used by LF amateurs. The Puckeridge site offered a unique opportunity to do this, since as well as the existing big 99m (325ft) beacon antenna, which has been described before, it was > possible to put up a small, amateur-style inverted 'L' antenna. > > The vertical part of the L was 9m high and about 130m to the south of the main mast. The single 24/0.2 top wire (about 1mm diameter) ran directly away from the main mast, and was 42m long. The whole of the small antenna was off the main ground system, which extended over a circular area for about 120m from the base of the mast. The small antenna ground system had 4 ground rods, 1m long, spaced a couple of meters around the antenna tuner. The fencing wires that ran under the antenna, about 50m long, were also bonded to the small antenna ground, and were not connected to any other fences. > > Both antennas shared a near-ideal location on top of a small hill, surrounded by quite flat agricultural land with open fields. At the same time, the antennas were far enough apart to have only loose coupling. > > The small antenna was remotely tuned by a motor-driven variometer. the big antenna's matching circuit was fed through what was effectively a power attenuator, which could be adjusted for the same radiated power as the small antenna. Either antenna could be selected using a change-over switch. To minimise coupling, the big antenna was grounded by another contact on the switch when the small antenna was selected. Also, the long leads to the small antenna had common-mode ferrite chokes, to prevent earth currents flowing through them to the main antenna ground. > > I set up the system by monitoring the current (Iant) in both antennas. This eliminated the need to take into account losses in the matching networks and cables, which were significant. To calculate the radiated power (=Iant^2*Rrad), the following antenna currents and radiation resistances (Rrad) were used: > > Inverted L - Rrad = 0.020 ohms, > Iant = 2.1A, > Radiated power = 88mW > > 99m Vertical - Rrad = 0.65ohms, > Iant = 0.36A, > Radiated power = 84mW > > The radiation resistance estimates were based on the simple formulae (see, for example, ON7YD's web pages), EZNEC simulations, and for the big antenna, calculations based on the quoted efficiency figures. These were all roughly in agreement. Exactly equal radiated power was not possible, because the attenuation could only be varied in steps, but the difference is only 0.2dB. Generating these currents required about 240W into the small antenna, but only 0.7W into the big antenna. > > The radiated powers are "EMRP", ie. effective monopole radiated power, assuming that both antennas have the radiation pattern of a theoretical short, vertical monopole. The ERP (ie. effective radiated power relative to an ideal dipole antenna) can be calculated by adding 2.6dB to the EMRP or multiplying by 1.8. The apparent increase in power is because of the presence of a ground plane, resulting in the monopole having greater directive gain. ERP appears to be the quantity specified by the BR68 booklet, containing the regulations for UK amateurs. The corresponding ERP's are 159 and 151mW respectively > > Using this set-up, I received 12 comparative reports during QSO's, plus 2 listenter reports, and I also did 2 sets of short range field strength measurements. Out of the total of 16 results, one report was that the big antenna was 4dB up on the small antenna, one indicated no difference. The remaining 14 indicated that the signal from the small antenna was on average 4dB stronger (between 3dB and 6dB or 1 's' point). The most likely cause of the 2 divergent results is, in my view, operator error - for example, I might have sent 'big' when I meant 'small', or forgotten to operate the switch. Of course, other sources of error also exist. The reports were received over a wide range of distance and direction, so the 4dB advantage of the small antenna under these conditions seems clear. > > With a couple of stations, I also tried the effect of having the big antenna in a resonant condition while transmitting from the small antenna. They reported the difference was no more than 1dB. The antenna current flowing in the big antenna under these conditions was less than 0.1A, so the re- radiated power must have been only a few mW. With the big antenna grounded, there was no visible deflection of it's ammeter due to power from the small antenna. This indicates that coupling between the antennas was not a significant factor. > > On the receive side, There was little to choose between the antennas. With the transmit attenuator in place, signals from the big antenna were aproximately 3dB down on the small antenna. The signal-to-noise ratio was practically the same. Flicking between one antenna and the other, it was hard to tell the difference. If anything, the small antenna was a very slight improvement on some signals. > > How might the 4dB difference in radiated power between the two antennas arise? It could be put down to a relative error in current measurement of about 60%, but since I used the same instrumentation to calibrate both ammeters, this is extremely unlikely. I believe this source of error is not likely to be more than 1dB. The other possibility is that the values of radiation resistance are incorrect, either the inverted L having greater than 0.02 ohms, or the vertical having less than 0.65 ohms, or some combination of both these changes. > > In order to experimentally check the values of ERP and radiation resistance, field strength measurements are required. Knowing the field strength and distance enables the actual ERP to be calculated. I measured the field strength using a Rycom 3136 selective voltmeter and home-brew ferrite rod antenna, which had previously been calibrated against commercial field strength measuring equipment. Two sets of measurements were made at two sites, one 4.1km north of the main antenna, the other 2.5km to the south. ERP was calculated using the formula: > > P = (E*r/7)^2, where E is field strength in mV/m, > r is distance in km > > The two results for each antenna were within 1dB of each other. The average result for the big antenna was 85mW ERP. This is 2.6dB below the calculated value. The average result for the small antenna was 230mW ERP, 1.5dB greater than the calculated value. The measurements give an ERP not very far from the theoretical value for both antennas; however, the field strength measurements confirm the small antenna generates about 4dB greater radiated signal. > > The conclusions from these experiments are: > > -The 99m Decca mast is a much more efficient antenna than the 9m inverted L (about 13% as against 0.08%) at 136kHz. > > -The comparative reports on the whole show that the small antenna gave a signal about 4dB stronger than the big antenna, irrespective of distance or direction. No noticeable directional effects occured. This agrees with the theory, which says both antennas should have the same radiation pattern. > > -The field strength measurements showed that the 9m inverted L generated 1.6dB more radiated power as predicted by theory, and the 99m vertical 2.5dB less. It should be remembered that +/-2dB would be considered 'good' accuracy for field strength measurements, and so both these results are in reasonable agreement with theory. However, the field strength measurements confirm that the small antenna radiated about 4dB more power than the big one. > > The implication for LF amateurs are that: > > -Provided you maintain ERP at the same level, there is no advantage or disadvantage to a small vertical antenna over a big one for LF transmitting - both antennas have the same radiation pattern. Of course, this requires greatly increased transmitter power for the small antenna to acheive the same result, which might well be considered a disadvantage. > > -There is no disadvantage in using a small antenna for receive - assuming the local noise level is acceptable, and the receiver sensitivity is adequate. At Puckeridge, the limiting factor on receive sensitivity was the Loran sidebands or QRN, depending on the time of day, which is the same as the situation at my home QTH. > > Finally, two interesting issues arise: > 1) Why does the small antenna apparently radiate more efficiently than it should? > 2) Why do similar small antennas (eg. the one at my home QTH, and G3XDV's antenna) radiate fields several decibels lower than expected from theory? (The "missing decibels" detected in previous field strength experiments). > > The 9m high, 42m long inverted L will just about fit in my garden - over the next couple of weeks, I plan to put it up there, and do some more field strength measurements. This will give a comparison between the same antenna in different environments. Watch this space... > > ________________________________________________ From akestelo at bellatlantic.net Sun May 28 10:26:36 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:09 2003 Subject: [Lf] LF receiver for sale Message-ID: <39311E8C.C6316E3F@bellatlantic.net> Bob Roehrig wrote: > I have a National RBL that needs a new home. It is a navy WW2 era regen > set that tunes 15 to 600 kHz. WOrks great - just no room for it here. > $20.00 takes it. The catch is you have to come get it. It is 75 lbs so no > way will I ship it. I am 40 miles west of Chicago. > > "Nostalgia is a thing of the past" > E-mail: broehrig@admin.aurora.edu or k9eui@arrl.net 73 de Bob, K9EUI > CIS: Data / Telecom Aurora University, Aurora, IL > 630-844-4898 Fax 630-844-4222 > PLEASE PUT ALL REPLIES IN ASCII TEXT ONLY > > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From akestelo at bellatlantic.net Mon May 29 10:08:12 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:10 2003 Subject: [Lf] Little and Large antennas] Message-ID: <39326BBC.CC2ED944@bellatlantic.net> vernall wrote: > g3kev wrote: > > > > Avoid large antennas if possible because to date I have blown the front > > ends of two TS850'S, one TS50 and one FT890. The static collected and > > discharged by large vertical antennas must be seen to be believed. The > > normal precautions like gas discharge devices do not always work. I have > > seen the sparks jump some inches across from the antenna to the nearest > > ground/earth. Maybe an auto spark plug suitably adjusted would be > > better. > > Many commercial stations use a "static drain" in the form of a large > value RF choke, from the base of the antenna to ground. Of course, the > choke has to be a high impedance at the band of transmission, with no > self-resonances, etc. If there is a direct lightning strike then it is > goodbye choke, and probably more, but for other times an RF choke drains > off incidental static. > > Experience in New Zealand is that receiving off a large antenna can > invite local QRM from near fields, making received S/(QRM+QRN+N) worse > than using a smaller antenna such as an active whip. Usually the > receiver noise figure is not the limiting condition, and a small > receiving antenna can perform very well. > > If a big antenna is used for receive, an external 20 dB attenuator could > save a blow up inside a TS-850 or equivalent receiver, and still not > miss a QSO in terms of system sensitivity? > > Bob ZL2CA From akestelo at bellatlantic.net Mon May 29 17:08:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:10 2003 Subject: [Lf] Lightning map of North America Message-ID: <3932CE54.8A485E99@bellatlantic.net> "Haase,Kent [Wpg]" wrote: > For a map of most of NA, go to > > http://www.weatheroffice.com/default.asp?page=LightningNews/default.htm > > although this one is not updated as often as the map below. > > Kent E. Haase > Environment Canada > Data Acquisition Specialist > Technical Services - Winnipeg > > -----Original Message----- > From: Lyle Koehler [mailto:lyle@mlecmn.net] > Sent: Monday, May 22, 2000 22:40 > To: LowFER reflector; Longwave Message Board > Subject: [Lowfer] Lightning map of the US > > Want to know where all that QRN is coming from? Go to > http://www.lightningstorm.com/lightningstorm/gpg/lex1/mapdisplay_free.jsp > -- > Lyle, K0LR From akestelo at bellatlantic.net Mon May 29 22:34:11 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:10 2003 Subject: [Lf] Antennas: Surge arrestors and lightning] Message-ID: <39331A92.B84817E5@bellatlantic.net> Alan Melia wrote: > I am no expert on lightening protection but I did work about 30 years ago on > high voltage protection of (the pre-optical) submerged repeater amplifiers. > These are power-fed in series and when your friendly Trawlerman gets snagged > and puts his axe through the cable, it is in effect shorting 7 miles of coax > (100pf per foot or so) charged up to anything up to 15kV. We used gas > discharge tubes to protect the power supply together with BIG Zeners. The > gas tubes have to be specially made (I have never quite understood what the > little neons on the old wartime BC348 and command sets were supposed to do) > The problen with discharge tubes in the dark is that eventually all the odd > ions recombine, then when you want the tube to strike it has to reach very > high voltages before it will take current. Purpose built (gas) surge > arrestors have a small amount of radioactive material in them to ensure that > there are always a few ions floating around to start the breakdown avalanche > off. I think that gas tubes took somewhere in the order of a few hundred > microseconds to fire, but they took the brunt of the power. > > The amplifier input was a 3:1 step up transformer feeding the base of a > bipolar transistor. Having found some diodes that would absorb 10kV for > 5usecs we put a pair across the the transformer input. We found that whilst > they protected the transformer from fusing, in this position they did not > protect the transistor. We found the transformer 'rang' and produced a surge > in the secondary that destroyed the transistor. So a second pair of back to > back diodes was connected directly across the base and ground. As these > where wideband amps, intermod was inportant so we actually used a pair of > diodes in series in parallel with another pair with reversed polarity. The > reason for this is that the capacity of a junction diode varies with the > square of the voltage applied, so if you half the voltage swing you reduce > the capacity variation by a factor of 4, and a resultant improvement in the > intercept points.The diodes used were a standard in the 1N3595 range from > Fairchild. The secret being a large 'S' shaped spring with a reasonable > thermal inertia that made contact to the top of the diode chip, and absorbed > the rapid rise in temperature at the junction. The output stage was > protected by a zener and small diode in series, the zener providing a > 'hold-off' voltage. > > I noted that my old FT101ZD had a small 'lamp-fuse' in series with the > aerial feed to the receiver section. Induced voltages took that out but it > obviously protected the rx front-end. > > I would suggest a spark gap might be the best safety device ....2 sharp > points about half a cm apart (it probably depends on the rf voltages around > but air breaks down at about 10kV per cm gap , I think) What you must watch > is that if the static causes a flashover whilst you are transmitting the > spark will be maintained by the RF even though the voltages are not enough > to initiate a discharge. The safest way is Mal's....ground it all and go and > make a cup of tea until the storm passes. > > Cheers de Alan G3NYK > Alan.Melia@btinternet.com From akestelo at bellatlantic.net Tue May 30 00:26:45 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:10 2003 Subject: [Lf] [Fwd: LF: Surge arrestors and lightning] Message-ID: <393334F4.4D852B78@bellatlantic.net> Doc Gruis wrote: > Thank you for these interesting posts. > > I have had minimal lightning problems over the years I have been doing > radio type things. I have high hopes of a new antenna this summer for > the next season. On the last 45 foot mast, I had a small gas engine > spark plug between the bottom of the antenna and ground / earth. It > showed some pits on its points so it must have done something! The > little neons across the inputs on WW-II type gear were used for several > years. Perhaps they helped with some slight noise reduction or were > talismans of sorts, but the fact that they were used for several years > indicates they must have had some marginal utility. A direct strike is, > of course, devastating, but the field around it is more easily > dissipated. Confession: I still use them from time to time. And, then > again, maybe they would just dissipate local static. I have noticed a > slight noise reduction in putting a NE-2 in parallel with a high > resistance static drain resistor. > > Regarding the gas tubes sparked (pun unintentional - but not deleted) a > memory about the "keep alive voltage" in radar T-R switches... > > 73, > > Doc, K0HTF and Long Wave "D" > Iowa, USA, EN31 > ______________________ > > Alan Melia wrote: > > > > I am no expert on lightening protection but I did work about 30 years ago on > > high voltage protection of (the pre-optical) submerged repeater amplifiers. > > These are power-fed in series and when your friendly Trawlerman gets snagged > > and puts his axe through the cable, it is in effect shorting 7 miles of coax > > (100pf per foot or so) charged up to anything up to 15kV. We used gas > > discharge tubes to protect the power supply together with BIG Zeners. The > > gas tubes have to be specially made (I have never quite understood what the > > little neons on the old wartime BC348 and command sets were supposed to do) > > The problen with discharge tubes in the dark is that eventually all the odd > > ions recombine, then when you want the tube to strike it has to reach very > > high voltages before it will take current. Purpose built (gas) surge > > arrestors have a small amount of radioactive material in them to ensure that > > there are always a few ions floating around to start the breakdown avalanche > > off. I think that gas tubes took somewhere in the order of a few hundred > > microseconds to fire, but they took the brunt of the power. > > > > The amplifier input was a 3:1 step up transformer feeding the base of a > > bipolar transistor. Having found some diodes that would absorb 10kV for > > 5usecs we put a pair across the the transformer input. We found that whilst > > they protected the transformer from fusing, in this position they did not > > protect the transistor. We found the transformer 'rang' and produced a surge > > in the secondary that destroyed the transistor. So a second pair of back to > > back diodes was connected directly across the base and ground. As these > > where wideband amps, intermod was inportant so we actually used a pair of > > diodes in series in parallel with another pair with reversed polarity. The > > reason for this is that the capacity of a junction diode varies with the > > square of the voltage applied, so if you half the voltage swing you reduce > > the capacity variation by a factor of 4, and a resultant improvement in the > > intercept points.The diodes used were a standard in the 1N3595 range from > > Fairchild. The secret being a large 'S' shaped spring with a reasonable > > thermal inertia that made contact to the top of the diode chip, and absorbed > > the rapid rise in temperature at the junction. The output stage was > > protected by a zener and small diode in series, the zener providing a > > 'hold-off' voltage. > > > > I noted that my old FT101ZD had a small 'lamp-fuse' in series with the > > aerial feed to the receiver section. Induced voltages took that out but it > > obviously protected the rx front-end. > > > > I would suggest a spark gap might be the best safety device ....2 sharp > > points about half a cm apart (it probably depends on the rf voltages around > > but air breaks down at about 10kV per cm gap , I think) What you must watch > > is that if the static causes a flashover whilst you are transmitting the > > spark will be maintained by the RF even though the voltages are not enough > > to initiate a discharge. The safest way is Mal's....ground it all and go and > > make a cup of tea until the storm passes. > > > > Cheers de Alan G3NYK > > Alan.Melia@btinternet.com From akestelo at bellatlantic.net Tue May 30 21:55:46 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:11 2003 Subject: [Lf] SAQ qrv on 17,2 kHz July 02] Message-ID: <39346312.40CCCDE5@bellatlantic.net> C Andersson wrote: > New transmissions scheduled from SAQ 17,2 kHz: > > http://www.telemuseum.se/grimeton/jubilee.html > > /Christer > sm6pxj From akestelo at bellatlantic.net Tue May 30 21:53:11 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:11 2003 Subject: [Lf] [Fwd: LF: DDS Board "Engineering model" works perfectly.] Message-ID: <39346277.33F08D4C@bellatlantic.net> Andy Talbot wrote: > To all interested in the DDS module. > (Larry could you pass on to others who don't monitor the LF reflector > please) > > I've had a proper artwork made and produced a couple of PCBs at home for the > AD9850 DDS module. Results with the home produced board aren't perfect as > my PCB material is quite old now, and UV exposure is a bit uncertain, but > one board is quite acceptable and the other just had to have a few whiskers > cleaned off with a hot iron. > > Today I've just assembled one board with a spare AD9850, and it works > perfectly as expected. What's more, that is after having to remove the IC > and replace it as I had carelessly trapped a tiny bit of solder which was > shorting two tracks under the chip (fortunately non fatal) and probably due > to the home produced PCB. Certainly don't recommend that procedure !!! > > I'll get in touch with the PCB manufacturer we've used before and get a > quote for 100 off. Should be reasonable if we don't put a tight timescale > on the job - say 3 - 4 weeks so the company can batch them with other jobs. > Meanwhile I'll do an initial write up and send that to all who have > contacted me directly so far (about 20). > > To those who aren't familiar with the story so far : > > This DDS module is a small PCB containing an AD9850 Direct Digital > Synthesizer with output filter and PIC controller chip. It is intended as a > drop in module for other projects rather than a stand alone pice of > equipment as are the QEX and G0MRF etc designs. For simple single > frequency programming an ASCII terminal is all that is required, but the > real aim was to provide a straightforward command set so that anyone can > write their own driver programmes without having to worry about the > intricacies of addressing the 9850 itself. > > It requires a clock source (0 - 5V level) at any frequency from DC to 120MHz > and interfaces with a PC via the serial RS232 link. The PC is used to set > frequency information and phase key the output using commands based on > simple text characters, frequency is stored in non volatile memory for > instant single frequency start up. The PIC software is written, but there > may still be a bit of fine tuning (no pun) that can be done on it yet while > waiting for the proper PCBs. One option that I'm not sure whether to add or > not, is the option of using the one PIC to control a second DDS as well, > with an additional set of commands. This would be mounted on a second PCB, > but without its own PIC, and interface to the controller using some of the > spare control lines. > > We haven't fully decided what to supply just yet - the PCB alone, with the > 9850 chip, a programmed PIC etc etc. Price is still to be fixed depending > on interest shown (and projected) and how much money we decide to put up > front in bulk purchasing. At some later time - a fully assembled module MAY > be available, but that depends on demand. Looking at replies received so > far, whilst a few would like a fully assembled unit, many would be happy > with just a PCB. > > Andy G4JNT > > mailto:ACTALBOT@DERA.GOV.UK During the working day or G4JNT@ARRL.NET > at other times From akestelo at bellatlantic.net Wed May 31 09:20:27 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:11 2003 Subject: [Lf] [Fwd: LF: Static discharge] Message-ID: <3935038B.A6C6C426@bellatlantic.net> Tom Boucher wrote: > In message <2000053009081868199@zetnet.co.uk>, Peter Dodd > writes > >Most of the istallations used by the LF group (and including the one > >at G3LDO) use a loading coil/tuning variometer/matching transformer > >arrangement that provides a DC path to ground so a large static build > >up does not occur. > > Peter, > > I am not sure that this is so. I used to use a tapped loading coil > arrangement with the bottom end grounded but after a discussion with > David G0MRF at Windsor last October, changed this to a simple series > loading coil which works just as well. > > David's theory was that in the case of the grounded coil, should the > antenna go off resonance for any reason, the impedance presented to the > transmitter will go very low and probably blow up the Tx. With a simple > series coil, if the antenna goes off tune, the impedance will rise and > not overload the Tx. However, there is no static discharge path. > > Another subject - I had a nice 136 KHz QSO yesterday with Howard G3RXH > in Skipton who was receiving me on an AR88-LF. One more for your list of > LF receivers! > > 73, Tom G3OLB. From akestelo at bellatlantic.net Wed May 31 09:28:52 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:11 2003 Subject: [Lf] Slow CW Vs. BPSK Message-ID: <39350583.7E60BD1B@bellatlantic.net> John Davis wrote: > Les Rayburn writes: > >The most obvious "pro" for Slow CW to me would seem to be that both the > >transmission and reception of these signals can be accomplished > >without major changes to anyone's Lowfer set up. > > > > Correct. That is its major advantage. > > BPSK has certain advantages in difficult conditions due to its ability to > make decisions based on accumulated data (frame grabbing), but this also > means the message must be repetitive and its duration must be known in order > to receive successfully under those conditions. In addition, if the > receiver isn't extemely close to the transmitted frequency, time and data > can be wasted while the software acquires the signal. > > QRSS has the advantage of not requiring you to know the frequency to the > nearest Hertz or wasting > time continuously sending redundant information, though it may take longer > to get the message in the first place under a given set of circumstances. > > >Also, would someone like to fill me in on the latest advances to > >the Slow CW program? It seems to make it possible to send > >a given amount of information in a shorter time frame. But it seems to > >me that would ultimately hurt the S/N ratio, right? > > Not necessarily. The dual frequency mode partially removes an inefficiency > that is inherent in Morse code; namely, that the symbols transmitted consist > of elements which are distinguished from each other by their durations, > which are integer multiples of the dot length, and by whether carrier is on > or off during those intervals. The bandwidth of a Morse transmission is > determined by the dot length, but the "bit rate" is a lot slower than the > bandwidth would suggest because of this need to distinguish between > elements. That's a pretty wasteful encoding scheme, but was necessary to > ensuring that the ear could discriminate between the elements of the symbols > reliably. > > The original QRSS retained this limitation. However, the dual frequency > mode substitutes a second frequency for the extra time used in sending a > dash. (In real-world conditions, some people apparently had trouble > distinguishing a string of dits or dahs from a single longer element, so > Rick also included a one second break between elements to provide a sort of > clock reference. That's why I say it partially removes the inherent > inefficiency.) > > For the default QRSS mode of three seconds per dot, one assumes a sub-Hertz > bandwidth. The frequency shift is typically 4 or 5Hz. One might therefore > suppose that the frequency shift imposes a substantial increase in > bandwidth, and thereby a large decrease in S/N. But this is not so. > > Bear in mind that the detection method is a visual display of a large number > of immediately adjacent channels, each filtered to milliHertz bandwidths. > The S/N ratio of each displayed spectrum line is independent of its > neighbors and is a function of its own bandwidth. So if you have enough > computing power, you can resolve hundreds of Hertz of receiver output into > several hundred of these skinny frequency slots with pretty amazing S/N. > Now...the frequency differential QRSS mode doesn't require you to include > the frequency slots between its high and low conditions (provided the > transmitter and receiver are reasonably stable, hi). It only requires you > to be able to distinguish the on/off states of two of those slots. > > That _is_ equivalent to an S/N reduction of 3db because you may indeed have > to decide which of the two lines you see on screen is valid at a given > moment in time, rather than only determining the validity of one. If you > have to take into account the power present in two channels of equal width, > that is a 3db difference. However, by eliminating waste in the coding > method, you have gained a nearly 5db increase in speed! Not a bad tradeoff. > > You could, of course, slow down the transmission to achieve something near > the original data throughput, and actually come out ahead on S/N due to the > reduction of coding waste. > > >Since time is not that critical in a one way transmission, I would think > >that slower was better. But perhaps a faster version would allow us > >to take advantage of short term enhancements in propagation? > > Perhaps, but such enhancements are relatively rare at LF. A whopping lot of > slow transmissions can take place while a faster station is spinning its > wheels waiting for propagation to cooperate...and with relatively low > chances of anyone randomly monitoring at just the right time, the odds of > the faster transmission ever being copied at all are pretty low. > > (That's based on random monitoring, as is applicable to conventional LowFER > activity. Coordinated monitoring, such as applies to the Transatlantic and > Transpacific efforts, would be a slightly different matter. I'd think one > would want to cover all bases in those projects: slow, not so slow, CW, > BPSK.) > > 73, > John > > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From akestelo at bellatlantic.net Wed May 31 17:17:45 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:12 2003 Subject: [Lf] Radiostation Grimeton] Message-ID: <39357369.1E9BA7E3@bellatlantic.net> An HTML attachment was scrubbed... URL: http://atanasoff.rf.org/pipermail/lf/attachments/20000531/9dac5224/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... 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Name: C:\TEMP\nsmailGF.gif Type: image/gif Size: 260 bytes Desc: not available Url : http://atanasoff.rf.org/pipermail/lf/attachments/20000531/9dac5224/nsmailGF.gif From akestelo at bellatlantic.net Wed May 31 18:41:47 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:12 2003 Subject: [Lf] Re: Radiostation Grimeton, radio times?] Message-ID: <3935871B.ACD1A5C0@bellatlantic.net> C Andersson wrote: > >>The transmitter will go on air at 8.30 and 8.45am. 0.30 and 0.45pm (GMT) > > According to the Swedish text the times are: 8.30, 8.45, 12.30 and 12.45 am (GMT) > Probably some language confusion is involved. > > Earlier this year, when I talked to one of the guys behind the "SAQ scene", he mentioned > the possibility to work cross band 17,2 kHz / 136 kHz. Nothing is said about this in > the official texts so I have asked the question again and I'm now waiting for answer. > > 73 > Christer > sm6pxj From akestelo at bellatlantic.net Wed May 31 18:43:39 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:12 2003 Subject: [Lf] Radiostation Grimeton, revised radio times Message-ID: <3935878B.1654BE59@bellatlantic.net> C Andersson wrote: > "According to the Swedish text the times are: 8.30, 8.45, 12.30 and 12.45 am (GMT)" > > Sorry, that didn't make much sense either ;-) > Too fast hitting the send button. > > Now, another try: > 8.30, 8.45 am. > 12.30, 12.45 pm. > > Four hours between the transmissions. > /Christer From akestelo at bellatlantic.net Fri Jun 2 09:36:18 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:12 2003 Subject: [Lf] Slow CW vs. BPSK. & Computer modes] Message-ID: <3937AA41.E3A381F2@bellatlantic.net> Talbot Andrew wrote: > >This is all-important. Extremely weak stations require considerable > >additional work by the 'computer between the ears' to decipher > >what is signal and what is noise on the screen - just like aural > >Morse, but visual. This accounts for several extra dB of gain, and > >however slow you send the Morse, this advantage is still available. > >It would take a very sophisticated computer to be as good. > > NO ! With these modes the computer is not doing anything to aid > extraction of the signal that could not be done with conventional > hardware. The 'several extra dB gain' is just there because more > noise has been filtered out. The brain is just looking at amplitude > changes in this narrow bandwidth and integrating over the signalling > period (looking at brightness over the length of a dot). > > All Spect.... is, is a bank of narrow filters. There is nothing in > theory to stop you making a crystal filter, or a whole bank of them this > narrow. For a display mechanism, a chart recorder - multiple pen ones > are available. All this technology was available in the 1950s as I'm > sure those who were around in that era will remember. > > All the computer does is make this much simpler and cheaper and > available to everyone, it is only a filter and display mechanism so > please can we stop referring to Spect... as computer modes. It can > be done in other ways. > > Coherent etc and PSK31 are computer modes, SPECT..... is not, it is > only a filter bank and display. > > Real computer / DSP modes mean making use of coherent detection and > error correction - and have nothing to do with the speed of the > signalling. > > There seems to be no appreciation on this newsgroup of the real value of > coherent detection - that is, having phase information available when > the signal is decoded and coherently locking to the signal carrier and > bit timing. Simple theory, as I covered in a previous email, shows > mathematically the considerable theoretical advantage of coherent > detection over non coherent, there is no dispute about this. > > SO unless your ears / eyes can respond to signal phase, is doesn't > matter how much personal pride says that the brain is a marvelous > computer, is will never compete against PSK : > > Given the same TOTAL overall signalling speed and comparing like with > like on the end to end link. > > Repeating CW characters time and time again has to be compared with true > error correction and low data rate signalling. > > Computer error correction does the same job as the eye interpreting > between the dots on Spect..., and with well chosen codes can do an > awful lot better. These optimum codes are only just beginning to appear > thanks primarily to the huge research effort funded by the mobile phone > industry, but hopefully Coherent etc will soon make use of them - the > equations are public information. The maths is similar, just the > implementation different. > > Coherent etc and PSK31 are computer modes, Spect... is not. > > Andy G4JNT > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution, > or any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From fgentges at mindspring.com Fri Jun 2 16:20:34 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:13 2003 Subject: [Lf] AMRAD LF Handbook project References: <393802E9.AC8D16A8@qwestinternet.net> Message-ID: <39380902.D05FA956@mindspring.com> Doug, We are glad to get your message. At AMRAD the current emphasis by many of us is on LF communications as you may have seen on our web page. We are currently working on projects leading to an LF handbook that would be published by ARRL for radio amateurs. ARRL has petitioned the FCC for LF allocations to be added to the amateur frequencies. This handbook would contribute to this direction. Based on your background you may be able to contribute to this effort. We have been looking at computer technology for several things: 1. Weak Signal spectral analysis and detection. We have some good stuff now with Spectran. We could use someone to work on an MSK weak signal program. Maximum Likelihood detection would fit in here very nicely. 2. Antenna design based on 1960's reports. We could use a computer model based on these old reports. (We have the reports) 3. LF Sky wave propagation based on curves etc. We could use a computer model based on this. We have some pretty good non computer data on this. 4. Electrostatic and Magnetostatic Field plots. We have been using QuickField (www.quickfield.com) which is a finite element analysis model. We could use some help in using this and would be ecstatic to find a model that would model 3 dimensional fields. This looks pretty hard to do and you will have to break out your Physics 101 and 102 books. 5. A general purpose LF calculating program for complex impedances etc. that will take care of complex math and decimal points for the DIYer at home. ARRL Radio Designer does this but we need a simpler, less expensive program we could include with the CD ROM in the book. Some of these may be more suitable for a school class or club group to look into. We have several other odds and ends. You may have some thoughts and we would like to hear them. Any help on these from you or anyone else reading the mail reflectors can be used. Frank Gentges K0BRA "D. Hansen" wrote: > > Dear AMRAD, > > I'm an electrical engineer and work in the data storage industry. For > years I've wanted to apply the technology I use at work to an amateur > radio application. I was wondering if possibly contributing to one of > your projects would be a good way to accomplish that goal. > > Here are my areas of expertise: > > 1) Design of analog ASIC (and discrete) circuits, > 2) Development of new read channel architectures, and > 3) Development of software models for simulating and evaluating read > channels. > > I've been interested in finding a way to adapt the "maximum likelihood" > detection methods used in disk and tape drives to binary radio > communication (such as code). What do you think? How do you think I > could best contribute to AMRAD's projects? > > Doug Hansen > WB6RGC > > _______________________________________________ > Tacos mailing list > Tacos@amrad.org > http://www.amrad.org/mailman/listinfo/tacos -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From akestelo at bellatlantic.net Fri Jun 2 09:46:34 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:13 2003 Subject: [Lf] Another Litz wire stripping method] Message-ID: <3937ACA9.C767E4A0@bellatlantic.net> James Moritz wrote: > Dear LF Group, > I recently salvaged some thick litz wire, and have been trying to > find a workable method of stripping the insulation. The enamel is of > the older, dark coloured type, which cannot be removed by dipping > in molten solder. The overall conductor thickness is about 4mm > with 729 strands, and a spirit burner as previously suggested on > this reflector just does not make any impression. A blowtorch does, > but also burns away the outer strands and the plastic sheathing. I > believe chemical strippers are available, but have to be melted at > high temperature, and then neutralised afterwards. > > However, the following seems to work quite well - strip about 50mm > of the plastic sheathing, and wrap the end 25mm of wire strands > tightly in a piece of copper foil (such as can be peeled off some > PCB laminate, or the type used for EMC shielding). Wrap a smaller > piece of foil around the 12mm of wire strands nearest the stripped > back sheathing, and grip with a pair of pliers - this acts as a > heatsink to protect the sheathing. Heat the foil covered end red hot > with a blowtorch. The enamel burns off with a small flame at the > end of the foil, while the foil protects the copper strands from the > blowtorch flame. When the flame goes out, leave to cool and > unwrap the foil. The wire strands are coated in black, shiny > residue, which can be cleaned off by rubbing the end of the wire > against the bottom of a shallow dish full of water, as if cleaning a > paint brush. Somewhat suprisingly, this leaves clean, shiny strands > of copper that can be soldered in the usual way. > > Just thought this might be useful to know, > Cheers, Jim Moritz > 73 de M0BMU From akestelo at bellatlantic.net Fri Jun 2 17:54:06 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:13 2003 Subject: [Lf] Slow CW vs. BPSK etc.] Message-ID: <39381EEE.2BFBAC49@bellatlantic.net> IMHO, a well written message, Andre' N4ICK ********************* WarmSpgs@aol.com wrote: > >There's a lot of discussion going on at the moment on the US "LowFER" > >mailing list about the relative merits of slow CW versus BPSK > > Indeed there has been. Some of it has gotten rather silly and occasionally a > bit abusive, in fact. I'm glad to see the discussion has been more civilized > here, although there are still evident tendencies to compare apples with > oranges and to draw too many conclusions from accepted premises. > > Some of the rather extreme arguments in favor of BPSK and similar modes tend > to count the same chickens twice; perhaps more often, for those claiming 23db > advantages . > > The most credible proponents say that, for a given bit rate, coherent methods > have a 9db advantage. Andy Talbot's post yesterday argues this case well. > Six decibels are the result of the effective doubling of detected signal > output by one state of the received signal adding in-phase and the other > adding out of phase in the detector. Integration of voltage over the symbol > period accounts for the other three. The latter effect is a direct > consequence of coherence (one might call it the definition of coherent > detection), and the former requires coherence to exist before it can be > true...or for any detection to exist at all. With coherence, a BPSK-based > mode has a 9db advantage over on-off keying detected non-coherently, or 6db > over coherent CW. > > Does this mean, therefore, that BPSK is inherently "better" than Slow CW? > Andy was careful to preface his comments with the qualification, "To compare > theoretically, firstly we need to make the assumption that data rates are > similar for the two modes." However, there is an additional qualifier that > follows from all this: we must also assume that coherence _can_ in fact be > achieved and maintained over the duration of enough symbols for the message > to be reconstructed. > > If this latter condition cannot be met, then PSK-based modes have no > advantage. They simply don't work at all. > > The traditional technique of reducing data rates and narrowing communication > bandwidth only work for coherent methods to the extent that the path between > the transmitter and receiver is stable enough to accomodate the slower bit > rate. It doesn't matter if the sender and receiver are using perfectly > synchronized atomic clock frequency standards: if propagation effects distort > the all-crucial phase information enough during each individual symbol, the > symbol will not be recovered. > > Hence, for a given propagation mode--and, where the ionosphere is involved, > this is also a function of carrier frequency, path length, launch angle, > geomagnetic conditions, and so on--there will be some _minimum_ data rate > below which a given coherent method will not work. Weak-signal reception > techniques based on power integration over extremely narrow bandwidths (i.e., > spectral analysis techniques) do not suffer nearly as strongly from the same > effects. > > Let's re-evaluate the numbers in this light. Suppose, over a given long > path, we find that BPSK will let us receive an acceptable percentage of a > transmission at 10 bits per second, but faster rates are limited by noise and > slower rates are limited by phase errors in the propagating medium. To > achieve the same result, we would have to slow down our on-off keying by 9db, > to roughly one dot per second. > > Now, however, let's suppose that either the noise levels increase, or we > attempt to receive the same signal over a greater distance. We can't slow > the speed of the BPSK transmission any further without losing the ability to > recover it coherently; which is to say, at all. Yet, we can slow down the CW > transmission and tighten the resolution of our receiving software and > continue the exchange of information. > > (This can't be done without limit, of course. At some point, propagation > phase shifts will spread the spectrum of the on-off carrier enough to > disperse it across multiple channels, considering how narrow the detected > channels have become at that point, and the analog signal-to-noise ratio will > then rapidly collapse too.) > > I don't follow the BPSK e-mail group, so this may not be the most current > information, but as far as I am aware, the best LF DX results with BPSK over > here have been at 100 and 200 milliseconds per bit. Some have tried 500 and > 1000 milliseconds, but have not done as well; whereas on HF, rates of 50 > milliseconds per bit or faster seem most effective. > > If 200 milliseconds per bit turns out to be the lowest practical speed for > longwave DX, then we already know that Slow CW at 3 seconds per bit should be > able to match its data recovery performance if the time penalty is > acceptable. We also know that 10 seconds per dot, or longer, is entirely > feasible with the available receiving software. The only thing we don't know > is how Slow CW performs under conditions of very long paths at LF, on the > order of 1600km or more at 5mw radiated power, for which we do have some > experience with BPSK. > > The essential point is that there are conditions below which coherent methods > cannot work at all, but in which other (slow) weak-signal methods may provide > at least a chance of getting signal through. There's room for a lot of > experimentation with these "different horses!" > > 73, > John KD4IDY From akestelo at bellatlantic.net Sun Jun 4 08:54:35 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:13 2003 Subject: [Lf] Photons again... Message-ID: <393A437B.2E4ADDAA@bellatlantic.net> If verified, an interesting development, Andre' N4ICK > http://www.sunday-times.co.uk/news/pages/sti/2000/06/04/stifgnusa01007.html From akestelo at bellatlantic.net Tue Jun 6 21:08:26 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:14 2003 Subject: [Lf] [Fwd: LF: Re: Antenna Z measurements at LF] Message-ID: <393D927A.AEC7C830@bellatlantic.net> Peter Dodd wrote: > Measurement of Antenna System Impedance at LF > > Although a suitable matching transformer can be arrived at > empirically the design can be simplified if the antenna feed > impedance is known. An impedance value will also give you some idea > of how good your ground system is, once you have estimated the coil > loss. There may be other uses. > > The method of measuring impedance I use is called the 3 Meter > Impedance Measuring Method (3m Z Bridge) and I have used it for the > last 20 years on HF. It is described in more detail in 'The Antenna > Experimenter's Guide' (from RSGB Bookshop). > The 3-meter impedance measurement technique is very simple. It > compares the unknown impedance with a fixed standard impedance, (a 50 > ohm resistor and a .01uF capacitor). An excitation source (signal > generator) applies an RF voltage to the standards and diode > voltmeters, selected by a switch allow digital voltmeter readings to > be made at various points. Impedance is indicated by the ratio of > three voltmeter readings. One additional reading allows in-place > calibration of the reference capacitor and the second permits several > solutions for the unknown impedance, thus giving an indication of the > random errors that may be present in the data. > Impedance values are derived from the voltage data by calculation. > However, this may be simplified by using a graphic method (using > graph paper and a pair of compasses and a ruler) or a computer. The > BASIC (do you remember that stuff?) source code is available at the > RSGB Web site If you download it as a text file it > will run in Q-Basic - I dont know about Visual Basic. > If you are using the standard Marconi antenna measure the feedpoint > impedance from the bottom of the loading coil and earth. > > The following measured impedances in the range 136.4 to 138kHz > indicate some errors just below 137kHz, which I have not yet identified. > > G3LDO_LF_Antenna > > Results +/-Errors > Freq MHz Res jX Res jX > ---------------------------------------- > .1364 37.9 - 29.4 2 2.1 > .1366 37.4 - 22.8 4.6 5.3 > .1368 33.5 - 22.2 5.1 5.7 > .1370 33.4 - 17.3 5.8 7.4 > .1372 35.6 - 8.8 2.8 3.5 > .1374 36.4 -0 1 1.7 2 > .1376 36.9 +0 5 1.1 1.3 > .1378 36.5 + 13.3 1 1.3 > .1380 38.1 + 21 1.1 1.8 > > The above measurements were made in the late afternoon when the > ground was relatively dry. In the morning the resistance was above > 40ohms and resonance was around 136.8kHz. > > A full description will appear in the forthcoming LF Book. > > -- > Regards, Peter, G3LDO > > From akestelo at bellatlantic.net Wed Jun 7 17:11:38 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:14 2003 Subject: [Lf] [Fwd: LF: DDS Board Progress] Message-ID: <393EAC7A.C0B512EB@bellatlantic.net> Talbot Andrew wrote: > The AD9850 DDS Board is now with the PCB manufacturers. I went there > yesterday to check the solder mask, and had a fascinating trip round the > factory looking at PCB manufacture and SMT component pick and place > mounting. Delivery is still quoted as 30 days so we have about 3 - 4 > weeks left as these are being batched with other PCBs. > > Price of the PCB will probably be ?8.00, plus p&p whatever that will > come out at. HF Instruments will also coordinate a bulk purchase of > AD9850 chips and some AD9851 devices too (see below), prices still to be > fixed. I have also been told that it will be possible to supply chips > mounted on the PCB for those frightened by the thought of soldering 28 > 0.65mm spaced pins - although its not as difficult as you might think > especially with a solder mask there to help avoid shorts underneath. > > The AD9851 DDS chip is pin compatible with the AD9850 device and has an > internal x6 clock multiplier allowing it to be used with up to a 30 MHz > oscillator to give a clock freqeuncy to 180 MHz - output range can then > go from DC to 70 MHz in steps of 0.04 Hz. For LF use however, I would > still recommend the AD9850 device with a drive frequency of 4 - 5 MHz > giving mHz steps. > One interesting aspect that comes out of the 9851 data sheet is the use > of the aliassed DDS products, after bandPASS filtering, to generate > frequencies in the VHF range up to 100s of MHz. Very useful to > microwavers. > > Andy G4JNT > > -- > The Information contained in this E-Mail and any subsequent correspondence > is private and is intended solely for the intended recipient(s). > For those other than the recipient any disclosure, copying, distribution,o > r any action taken or omitted to be taken in reliance on such information is > prohibited and may be unlawful. From fxfarmer at erols.com Thu Jun 8 11:17:43 2000 From: fxfarmer at erols.com (Bill) Date: Thu Jul 3 13:42:14 2003 Subject: [Lf] Activity on 168.125 kHz Message-ID: <393FAB07.3BE64DB@erols.com> I've been hearing an ON/OFF keyed carrier on 168.125 kHz. The ON time is on the order of 16 seconds and OFF time is about 24 seconds. The first 8 seconds of the ON time appears at full power (received here at -83 dBm), then the level shifts down 10 dB and remains ON for another 8 seconds (-93 dBm), before going off the air for 24 seconds. Have been hearing it since about 5AM this morning, and it doesn't appear to be getting any weaker as the day progresses. I'm using a 180' coax loop antenna and making the measurements on a RYCOM Model 6041. Wonder if any others are hearing this signal or can shed any light on it's origin or function ?? Bill Farmer W3CSW Rockville, Maryland From akestelo at bellatlantic.net Thu Jun 8 17:53:09 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:14 2003 Subject: [Lf] New software available for copying weak QRS-CW] Message-ID: <394007B4.825CD562@bellatlantic.net> Bill de Carle wrote: > CRUNCH Version 1.0 from VE2IQ > ----------------------------- > > Hams have been experimenting recently with ultra-slow speed CW (QRS-CW). > One standard is sending at around 0.4 words per minute, or 3 seconds > per dit. It takes a very long time to send a message and it cannot be > decoded by ear. Up to this point the technique for recovering the message > has been to display the spectral output from a FFT program on the computer > screen graphically, and try to pick out the dots and dashes with the > human eye. There are some advantages to this method - you don't have to > know the frequency very exactly and the eye can recognize patterns in > noise quite easily. There are also some disadvantages, mainly that the > eye doesn't work very well at discriminating subtle differences in > brightness or color and sometimes it is very difficult to determine > whether the key was down or up when all you have to go on is a display > full of background noise and a very faint trace that may or may not be > there. Even if we have 16-bits of precision in our processed data, > the eye can't use it. But how about the ear? High-fidelity buffs > will tell you they can "hear" the difference between 8-bit audio and > 16-bit audio. > > It occurred to me that hams have been copying CW by ear for a long time > and we seem to have developed a knack for digging weak signals out of > the noise by using the processing power between our ears, hi! Some CW > people are amazing in their ability to "hear" signals way down in the > noise. The human ear is very good at detecting coherent but very faint > audio signals in white noise and reading the CW under those conditions. > I also know that if we compress a slow-CW signal in time about 35 times > we can effectively reduce the bandwidth by 35 times and increase the > SNR correspondingly. > > I was trying for a day or so to copy VA3LK's ultra-slow CW signal and > not having much success. My FFTZZ program, when set for a long integration > period (15 minutes) was able to *detect* the signal and show its frequency > but I was not able to decode the message by any conventional means. > So I recorded about 10 minutes of the receiver's output and tried a few > tricks to process the resulting audio off-line. Eventually I was just > able to copy the message. I decided to write a program that would do > all the off-line steps in real-time, so we wouldn't have to tie up huge > amounts of disk space to store an overnight monitoring session. > > The first draft of this program is available on my web page. It's called > "CRUNCH" - why not download it and try it for yourselves? > > Go to http://www.ietc.ca/home/bill/bbs.htm > > The basic idea of this program is to time-compress very slow-speed CW > received off the air so that it can be played back about 35 times faster > and "heard" with the human ear. > > You will need a relatively fast computer (Pentium will certainly work, > maybe a fast 486?) - and one of my Sigma-Delta interface boards. You > do *not* need a sound card for recording, only for playback. So you > may be able to press an old laptop into service. CRUNCH runs under > DOS. You don't need Windows. It can use any serial port. You can > specify which port as a command-line parameter when you invoke the > program. (E.g. "CRUNCH COM=2"). > > The Sigma-Delta board samples received audio at 7,200 samples per second, > converts it to 8-bit digitized format, then sends it into the computer > via a standard serial port. The circuit is described on my web page and > also in my article "A Receiver Spectral Display Using DSP" which appeared > in Jan '92 QST. I still have parts kits available: contact me for > details if you're interested. > > DSP software running in the computer performs the following steps: > > 1. (optionally) passes the incoming audio through a narrow bandpass > filter centered on 800 Hz. This is a good idea when receiving slow-speed > CW because the signal bandwidth is minimal. The filter has a Butterworth > shape and a width (at the -3dB points) of 50 Hz. > > 2. Mixes the signal down to a target frequency of 22.5 Hz. > > 3. Lowpasses the output from the above mixer stage, then reduces the > sampling rate by some 32 times. Since there are no high frequency > components left at this point, we can completely capture the processed > audio tone with 225 samples per second, well over the Nyquist rate. > > 4. Saves the new sampled waveform into a 16-bit PCM (.wav) file, > stating in the .wav header the sample rate was 8000 samples per second. > > Saying that the sample rate was 8000 samples per second when in fact > it was only 225 results in two things: 1) a 35.55 x time compression, > and 2) multiplies the nominal 22.5 Hz derived carrier frequency back up > to 800 Hz, where it can easily be heard with the human ear. > > Even though the Sigma-Delta board is only an 8-bit ADC we still generate > a 16-bit .wav file because the 32x time compression plus the DSP filtering > makes 16 bits of useful resolution available at the lower sampling rate. > Sometimes a QRS-CW is so weak it can only be heard with 16-bit audio. > > The program may optionally capture data from the SD board in real time > (without compression) - but it will produce an 8-bit .wav file only in > this mode. Users are cautioned that leaving it running all night will > use up gobs of megabytes of hard disk space. > > How to set up an overnight monitoring run... > -------------------------------------------- > > The most usual operation will be to leave it running with the time > compression mode enabled. That way if you record 8-hours worth of > slow CW you will be able to play it back in the morning in just 13.5 > minutes! And you can be sure that if there's any CW in there you won't > miss a single word. You will of course have to be able to copy CW at > around 14 wpm by ear but that shouldn't be any real problem. Right? > > Since we *mix* the incoming audio down to 22.5 Hz (a frequency trans- > lation process) then *multiply* it back up to 800 Hz, it is relatively > important to know the exact frequency of the QRS-CW signal we're trying > to copy, even though it won't be audible in most cases. I strongly > recommend running FFTZZ for a few minutes to detect the presence of the > signal. If FFTZZ can't detect it after 15 minutes of integration > you're not going to be able to copy it anyway. You should set up FFTZZ > in its 8192-point FFT mode, with a frequency range of 700 - 900 Hz, and > integrate with the software AGC enabled. Any narrow audio filtering > you can do in the radio before the signal gets to the Sigma-Delta board > will only help - the bandwidth of the QRS-CW signal is essentially > nothing. After a while you will see a single spectral line making its > way up out of the background noise. That's the slow CW carrier. You > can now position the mouse cursor on that spectral line and read out > its frequency to the nearest Hz. Write the frequency down, you will > need it as an input to CRUNCH. The freq will have to be as close to > 800.0 Hz as possible - a few Hz either side is OK as long as you know > what the value actually is. You can adjust the audio level while > running FFTZZ - set it as high as you can without getting any of the > red "CLIPPING" messages. > > Bring up CRUNCH - and ask for the 800-Hz bandpass filter (default) and > the time-compression (also default). The program will ask you to enter > the exact frequency you wish to monitor (nominal 800.0 Hz). > > When it runs it will tell you each time it writes a 32K block of filtered > data to the output file. Each 32K block has 16384 16-bit audio samples > obtained at a rate of 225 samples per second, so it will write a new > block about every 73 seconds. > > You can let it run all night and stop it in the morning. > The resulting .wav file can be played back through any computer with > a sound card and the necessary software. And you can play around with > the audio - use your own noise reduction techniques or do additional > filtering. The Cool Edit program is real neat for that sort of thing. > > My own experience has been that the .wav file generated by CRUNCH is > just fine - and is easy to copy by ear. I have been able to get solid > copy on VA3LK's QRS-CW signal that I could not copy by any other means. > > Try it, you'll like it! > > Bill VE2IQ > > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From akestelo at bellatlantic.net Mon Jun 12 22:15:14 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:15 2003 Subject: [Lf] 1mW ERP, 600 miles... Message-ID: <39458B22.1F50D89E@bellatlantic.net> Alan Melia wrote: > [...] > Several of us have recently copied a QRS beacon from Marco running an > estimated 1mW ERP south of the Alps (900kms from me) I think this is well > into the area of powers being radiated by the Lowfer beacons allowing for > their frequency 50% higher, so their aerials are twice as efficient. From akestelo at bellatlantic.net Thu Jun 15 17:48:00 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:15 2003 Subject: [Lf] [Fwd: [Lowfer] Lowfer TV Documentary] Message-ID: <39494100.1152D8A5@bellatlantic.net> les@highnoonfilm.com wrote: > In a posting yesterday, I offered to edit a "lowfer documentary" that > would allow operators to showcase their beacons and allow > all of us to better share information with each other. > > It was suggested that each lowfer use a camcorder to tape this > and then send them to me for editing. I would then sell VHS > copies of the tape for cost (approximately $5). > > We've already gotten a lot of folks who seem to be interested in > this idea, with firm commitments from at least five beacon operators! > > Here's exactly what we're looking for: > > Any format (virtually) is fine. We can handle DV, Mini-DV, > VHS, High 8, and 8mm camcorder formats. What I am suggesting is > that folks take nice, long steady shots of each area of their > station (using a tripod if possible) and then record > themselves discussing the station in detail. > > Focus on the main areas, including antenna, tophat, grounding, > beacon keying, any measuring devices (RF Current meters, > final amp current, final amp voltage, etc.) > > Also, feel free to send me audio recordings of your beacon or > of other beacons. These can come to me on cassette or > via e-mail if there are .wav files or the like. I can handle virtually > any audio format and do have a ZIP drive as one person asked. > > Diagrams or digital stills are fine too. We have Photoshop 5.5 so > almost any format will work. Images need to be sized for 640 X 480 > pixels to fit on a TV monitor. > > A few folks suggested that we ask for people to show us their > receiving set up as well, including loops, pre-amps, beverages, > etc. I think this is a great suggestion. > > WA is in, and I'm very interested in his set-up, as he's running > those loops instead of a vertical... > > You can ship tapes to me at: > > Les Rayburn, KT4OZ > 4919 Cox Cove > Helena, AL 35080 > (205) 620-3473 > To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not > send to list!!) Send on list submissions to lowfer@qth.net From crippel at erols.com Thu Jun 22 11:56:29 2000 From: crippel at erols.com (Chuck Rippel) Date: Thu Jul 3 13:42:15 2003 Subject: [Lf] Excellent idea! Lowfer TV Documentary] In-Reply-To: <39494100.1152D8A5@bellatlantic.net> Message-ID: <3951F0DD.17398.26F3F2@localhost> What an excellent idea. I encourage you to proceed. > > > les@highnoonfilm.com wrote: > > > In a posting yesterday, I offered to edit a "lowfer documentary" that > > would allow operators to showcase their beacons and allow > > all of us to better share information with each other. ----------------------------- Chuck Rippel, WA4HHG R390 List Co-Administrator Reply to: wa4hhg@amsat.org To learn more about R390A's visit: http://www.avslvb.com/R390A/index.html 1968 Contract Dittmore-Friemuth R390A #38 1967 Contract EAC R390A #2808 with outboard Sherwood SE-3 Sync. Detector 1967 Contract EAC R390A #5295 1967 Contract EAC R390A #5591 1967 Contract EAC R390A #1023 All in regular use as premier Shortwave Broadcast DX Receivers -and- Vintage AM Amateur use -------------------------------- From fgentges at mindspring.com Sat Jun 24 21:02:20 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:15 2003 Subject: [Lf] Digitized Audio Message-ID: <39554C0C.5801133C@mindspring.com> Hi, At tacos today I mentioned that I was looking for a good method to digitize the 300 Hz bandwidth CW output of the RX320 to transmit remotely at something around 16 kilobits per second. I have looked at a few available options in WIN98 and at Xing's MP3 encoder. I would like to find the best option that will provide a good spectrogram with Spectran at the remote end. If I were to set the RX320 BFO for a 250 Hz, then the band should extend from 100 Hz to 100 + 300 = 400 Hz. But, the RX320 at 300 Hz bandwidth has quite a bit of energy beyond 500 Hz and you can hear the beat note come through zero which means significant artifacts could creep into the spectrogram. Simply put, the 300 Hz bandwidth has quite a bit of transition band beyond the 300 Hz edges before the signal is far enough down to ignore. One option would be to set the BFO for a 1 kHz center frequency like we do now for driving Spectran. The signal could be digitized and further filtered digitally in real-time yielding a 16 kilobit per second stream. A reverse process could then be used on the remote end. If this could have limited processing load it could be done in the PC. While we are at it we need to multiplex into the stream the RX320 signal strength data, but lets not get ahead of ourselves. Another option would be to use a streaming audio process like MP3 or the like to encode the audio. MP3 is an open specification and we should be able to use it freely. RealAudio might be an option but it is proprietary and does not seem to have a low rate option. Neither do we know the impact on Spectran of its artifacts. It would be nice to know how much we might be missing here. In the end, I would like to be able to put a remote RX320 and computer anywhere in the world and with a modem based internet (or modem direct) connection, be able to listen to the LF band. Any thoughts? Even better, any volunteers to work on this problem so we can put your solution in our handbook? Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From fgentges at mindspring.com Sun Jun 25 14:10:18 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:15 2003 Subject: [Lf] Re: Digitized Audio References: Message-ID: <39563CFA.266F5798@mindspring.com> Dave, Thank for the good comments. I tried a little MP3 encoding last night and by the time I got the data rate down low enough to be interesting the audio sounded reverberant. It indeed, encodes in strange ways on our signals. I have not had a chance to set up the notebook next to the desktop so I can try Spectran on it to see what it looks like. Your comments tend to lead me where I was thinking about going. We need our own compression/digitizing algorithm. Perhaps based on some existing algorithm like MPEG1 or MPEG2 with different clocking speeds. Perhaps better yet is a sharp skirted digital bandpass filter centered on 1 kHz followed by some sort of digitizer. If the digitizer is too adaptive it might choose to adapt to enhance the "noise" and suppress the "signal". MPEG 1 and 2 are public and available in Linux source code as I recall. If you want to try some stuff out I can make some typically poor s/n .wav files to test it out on. George brought by a couple of interesting pictures, one of you receiving the AMRAD award, the other a building where you work. Congrats David. Frank "David W. Borden" wrote: > > Frank, > > I wanted to do this last year but Shawn pointed out that MP3 encodes in > strange ways. It picks the loudest frequency and declares it dominant and > trashes everything else. For example if you are recording a room full of > people and they are all talking quietly and then some one starts shouting, > MP3 will encode the shouter at the expense of all others. > > My idea was to have a number of remote receivers all sending their stuff > by internet streaming audio to a central point where the audio was combined > and then sent to the DSP for recovery of stuff below the noise. Jim > Broyles (KA9GCS) produced me a combiner circuit (a bunch of op amps) that > combined all the streams to send to the DSP. It sounds like a neat idea > (the old space diversity) but MP3 won't do it as it will trash the very > good stuff I want to recover with the DSP. So maybe Real Audio. You have > to pay money to get the Real Audio encoder. My professor at UM did it last > year for his classes, he sent us his lecture in Real Audio. It sounded > super, but then there was not any super quiet signal in the background to > recover.......david > > At 20:02 6/24/2000 -0400, you wrote: > >Hi, > > > >At tacos today I mentioned that I was looking for a good method to > >digitize the 300 Hz bandwidth CW output of the RX320 to transmit > >remotely at something around 16 kilobits per second. I have looked at a > >few available options in WIN98 and at Xing's MP3 encoder. > > > >I would like to find the best option that will provide a good > >spectrogram with Spectran at the remote end. > > > >If I were to set the RX320 BFO for a 250 Hz, then the band should extend > >from 100 Hz to 100 + 300 = 400 Hz. But, the RX320 at 300 Hz bandwidth > >has quite a bit of energy beyond 500 Hz and you can hear the beat note > >come through zero which means significant artifacts could creep into the > >spectrogram. Simply put, the 300 Hz bandwidth has quite a bit of > >transition band beyond the 300 Hz edges before the signal is far enough > >down to ignore. > > > >One option would be to set the BFO for a 1 kHz center frequency like we > >do now for driving Spectran. The signal could be digitized and further > >filtered digitally in real-time yielding a 16 kilobit per second > >stream. A reverse process could then be used on the remote end. If > >this could have limited processing load it could be done in the PC. > >While we are at it we need to multiplex into the stream the RX320 signal > >strength data, but lets not get ahead of ourselves. > > > >Another option would be to use a streaming audio process like MP3 or the > >like to encode the audio. MP3 is an open specification and we should be > >able to use it freely. > > > >RealAudio might be an option but it is proprietary and does not seem to > >have a low rate option. Neither do we know the impact on Spectran of > >its artifacts. It would be nice to know how much we might be missing > >here. > > > >In the end, I would like to be able to put a remote RX320 and computer > >anywhere in the world and with a modem based internet (or modem direct) > >connection, be able to listen to the LF band. > > > > >Any thoughts? Even better, any volunteers to work on this problem so we > >can put your solution in our handbook? > > > >Frank > >-- > >Frank Gentges > >K0BRA, ex AK4R, W3FGL > >Check out our LF web page at > > > >_______________________________________________ > >Tacos mailing list > >Tacos@amrad.org > >http://www.amrad.org/mailman/listinfo/tacos > > -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From vdetomasi at tiscalinet.it Sun Jun 25 23:43:41 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:42:16 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> Message-ID: <39567D0C.7007FB45@tiscalinet.it> Hi Frank and the list, here are my opinions on your problem: if you want to digitize a receiver outbut and still be able to detect very faint signals buried under the noise, forget about audio compression, like MP3, RA, GSM, and so on! The reason is quite simple: compression (as well as denoising!) is done designing a suitable mathematical model that is fitted to the signal. Best fit is obtained by minimizing the energy of the difference signal (input minus modeled signal): computationally efficient methods exist to compute the signal model that fits at its best the incoming data. The difference between input signal and the model is simply discarded, and the transmitted information is the one needed to build up the model. MP3 adds to the best fitting process a psychoacoustic model: suppose that you listen to a 1000 Hz signal. Now add a 1500 Hz signal, and increase its amplitude until you hear it. Turn it off, and do the same for a tone at 1010 Hz: you will need quite a larger amount of signal to become aware that the tone at 1010 Hz is played with the steady 1000 Hz tone. MP3 encoders recognize the presence of tone pairs, and apply dynamic compression, i.e. they use a coarser signal quantization when a weak tone is close to a strong one. Imagine this kind of processing applied to VLF signals.... The best compression to do is Nyquist compression: if you have B Hz of bandwidth, sample them at a rate equal to 2B (maybe a little more, just to avoid aliasing), and use a suitable number of bits to get the needed dynamic range. So for a data stream of 16 kbit/s, you can transmit 500 Hz of bandwidth with 16 bit (i.e. about 96 dB of dynamic range, not bad...). Amplitude data can be encoded into the data stream replacing say a sample every 16k, so getting an amplitude measurement every second. The "lost" sample will be silently ignored also by the most sophisticated DSP engine. However there is a more efficient method: why don't you simply transmit the frequency spectrum ?!? I suppose you have a two way data channel, so you can think of sending commands to the "DSP server" in order to transmit you the desired frequency slice. What do you think about this ?!? vy 73 Vittorio IK2CZL > Today's Topics: > > 1. Digitized Audio (Frank Gentges) > > ------------------------------------------------------------------------ > > Subject: [Lf] Digitized Audio > Date: Sat, 24 Jun 2000 20:02:20 -0400 > From: Frank Gentges > Organization: K0BRA > To: LF@AMRAD.org, tacos@AMRAD.org > > Hi, > > At tacos today I mentioned that I was looking for a good method to > digitize the 300 Hz bandwidth CW output of the RX320 to transmit > remotely at something around 16 kilobits per second. I have looked at a > few available options in WIN98 and at Xing's MP3 encoder. > > I would like to find the best option that will provide a good > spectrogram with Spectran at the remote end. > > If I were to set the RX320 BFO for a 250 Hz, then the band should extend > from 100 Hz to 100 + 300 = 400 Hz. But, the RX320 at 300 Hz bandwidth > has quite a bit of energy beyond 500 Hz and you can hear the beat note > come through zero which means significant artifacts could creep into the > spectrogram. Simply put, the 300 Hz bandwidth has quite a bit of > transition band beyond the 300 Hz edges before the signal is far enough > down to ignore. > > One option would be to set the BFO for a 1 kHz center frequency like we > do now for driving Spectran. The signal could be digitized and further > filtered digitally in real-time yielding a 16 kilobit per second > stream. A reverse process could then be used on the remote end. If > this could have limited processing load it could be done in the PC. > While we are at it we need to multiplex into the stream the RX320 signal > strength data, but lets not get ahead of ourselves. > > Another option would be to use a streaming audio process like MP3 or the > like to encode the audio. MP3 is an open specification and we should be > able to use it freely. > > RealAudio might be an option but it is proprietary and does not seem to > have a low rate option. Neither do we know the impact on Spectran of > its artifacts. It would be nice to know how much we might be missing > here. > > In the end, I would like to be able to put a remote RX320 and computer > anywhere in the world and with a modem based internet (or modem direct) > connection, be able to listen to the LF band. > > Any thoughts? Even better, any volunteers to work on this problem so we > can put your solution in our handbook? > > Frank > -- > Frank Gentges > K0BRA, ex AK4R, W3FGL > Check out our LF web page at > > ------------------------------------------------------------------------ > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "Wir muessen wissen; wir werden wissen" (David Hilbert) From fgentges at mindspring.com Sun Jun 25 22:07:51 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:16 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> <39567D0C.7007FB45@tiscalinet.it> Message-ID: <3956ACE7.E7BB82CD@mindspring.com> Vittorio et al, I am hoping there is a free lunch out there in the compression schemes that are becoming so common. Your reply, another reply from David Borden (AMRAD Texas), and my own experimentation lead me to believe that MP3 is too speech specific and it does "strange things" to weak LF signals. I suspect the others to a lesser degree will also introduce bad artifacts into the signal but also compress less. "Less tasty and less nutrition." Doing a strong job of getting down to nyquist on a band narrowed signal seems the most likely way to get there now. Your suggestion of remotely computing the spectrogram and then transmitting the "spectrum picture" had occurred to me. For now I think even reducing bandwidth to 200 Hz to meet our goals would give more flexibility at the local site without losing the signal. My current thinking is to use a 750 Hz BFO frequency. Then filter the audio data through a 600-900 Hz FIR bandpass filter to cut energy way down, (60 db?) below 500 and above 1000 Hz. Initially sample this audio at 2000 samples per second to go into the digital FIR filter. This is based on there being no energy above 1000 Hz to avoid that alias. Then we have a 2000 samples per second rate of the output data stream of the FIR. We take every other FIR output sample to achieve a 1000 sample per second rate and throw the rest on the floor as they have no new information. We would have a mirror image alias on the other side of 500 Hz that would just be ignored or filtered out with a high pass filter. That gets us 16000 bits per second if we transmit 16 bit samples. The FIR filter may be a bit too much computation for a PC but I don't have experience with that yet. Any thoughts anyone? Does this work? Can we do it in background on a 486 "Dumpster Grade" Linux PC or should we build a dedicated filter? Can the sound card be run at 2000 samples per second under Linux or do we take every nth sample? Thanks Vittorio for helping us kick the ball forward on this. Frank Vittorio De Tomasi wrote: > > Hi Frank and the list, > > here are my opinions on your problem: > > if you want to digitize a receiver outbut and still be able to detect > very faint signals buried under the noise, forget about audio > compression, like MP3, RA, GSM, and so on! > > The reason is quite simple: compression (as well as denoising!) is done > designing a suitable mathematical model that is fitted to the signal. > Best fit is obtained by minimizing the energy of the difference signal > (input minus modeled signal): computationally efficient methods exist to > compute the signal model that fits at its best the incoming data. The > difference between input signal and the model is simply discarded, and > the transmitted information is the one needed to build up the model. > > MP3 adds to the best fitting process a psychoacoustic model: suppose > that you listen to a 1000 Hz signal. Now add a 1500 Hz signal, and > increase its amplitude until you hear it. Turn it off, and do the same > for a tone at 1010 Hz: you will need quite a larger amount of signal to > become aware that the tone at 1010 Hz is played with the steady 1000 Hz > tone. MP3 encoders recognize the presence of tone pairs, and apply > dynamic compression, i.e. they use a coarser signal quantization when a > weak tone is close to a strong one. Imagine this kind of processing > applied to VLF signals.... > > The best compression to do is Nyquist compression: if you have B Hz of > bandwidth, sample them at a rate equal to 2B (maybe a little more, just > to avoid aliasing), and use a suitable number of bits to get the needed > dynamic range. So for a data stream of 16 kbit/s, you can transmit 500 > Hz of bandwidth with 16 bit (i.e. about 96 dB of dynamic range, not > bad...). > > Amplitude data can be encoded into the data stream replacing say a > sample every 16k, so getting an amplitude measurement every second. The > "lost" sample will be silently ignored also by the most sophisticated > DSP engine. > > However there is a more efficient method: why don't you simply transmit > the frequency spectrum ?!? I suppose you have a two way data channel, so > you can think of sending commands to the "DSP server" in order to > transmit you the desired frequency slice. What do you think about this > ?!? > > vy 73 > > Vittorio IK2CZL > > > Today's Topics: > > > > 1. Digitized Audio (Frank Gentges) > > > > ------------------------------------------------------------------------ > > > > Subject: [Lf] Digitized Audio > > Date: Sat, 24 Jun 2000 20:02:20 -0400 > > From: Frank Gentges > > Organization: K0BRA > > To: LF@AMRAD.org, tacos@AMRAD.org > > > > Hi, > > > > At tacos today I mentioned that I was looking for a good method to > > digitize the 300 Hz bandwidth CW output of the RX320 to transmit > > remotely at something around 16 kilobits per second. I have looked at a > > few available options in WIN98 and at Xing's MP3 encoder. > > > > I would like to find the best option that will provide a good > > spectrogram with Spectran at the remote end. > > > > If I were to set the RX320 BFO for a 250 Hz, then the band should extend > > from 100 Hz to 100 + 300 = 400 Hz. But, the RX320 at 300 Hz bandwidth > > has quite a bit of energy beyond 500 Hz and you can hear the beat note > > come through zero which means significant artifacts could creep into the > > spectrogram. Simply put, the 300 Hz bandwidth has quite a bit of > > transition band beyond the 300 Hz edges before the signal is far enough > > down to ignore. > > > > One option would be to set the BFO for a 1 kHz center frequency like we > > do now for driving Spectran. The signal could be digitized and further > > filtered digitally in real-time yielding a 16 kilobit per second > > stream. A reverse process could then be used on the remote end. If > > this could have limited processing load it could be done in the PC. > > While we are at it we need to multiplex into the stream the RX320 signal > > strength data, but lets not get ahead of ourselves. > > > > Another option would be to use a streaming audio process like MP3 or the > > like to encode the audio. MP3 is an open specification and we should be > > able to use it freely. > > > > RealAudio might be an option but it is proprietary and does not seem to > > have a low rate option. Neither do we know the impact on Spectran of > > its artifacts. It would be nice to know how much we might be missing > > here. > > > > In the end, I would like to be able to put a remote RX320 and computer > > anywhere in the world and with a modem based internet (or modem direct) > > connection, be able to listen to the LF band. > > > > Any thoughts? Even better, any volunteers to work on this problem so we > > can put your solution in our handbook? > > > > Frank > > -- > > Frank Gentges > > K0BRA, ex AK4R, W3FGL > > Check out our LF web page at > > > > ------------------------------------------------------------------------ > > _______________________________________________ > > lf mailing list > > lf@amrad.org > > http://www.amrad.org/mailman/listinfo/lf > > -- > ************************************************************************* > Vittorio De Tomasi ik2czl@amsat.org > Home page: http://space.tin.it/scienza/vdetomas > My DSP page: http://www.freeyellow.com/members/padan > > "Wir muessen wissen; wir werden wissen" (David Hilbert) > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From dibene at usa.net Mon Jun 26 11:22:54 2000 From: dibene at usa.net (Alberto di Bene) Date: Thu Jul 3 13:42:17 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> <39567D0C.7007FB45@tiscalinet.it> <3956ACE7.E7BB82CD@mindspring.com> Message-ID: <395712DE.EA35CCC9@usa.net> Frank Gentges wrote: > [snip] > Any thoughts anyone? Does this work? Can we do it in background on a > 486 "Dumpster Grade" Linux PC or should we build a dedicated filter? > Can the sound card be run at 2000 samples per second under Linux or do > we take every nth sample? > [snip] Frank, for longish FIR filter, a better solution is to implement them with the FFT. In Hamview the bandpass filtering was done with a couple of FFT / IFFT, with out-of-band rejection up to 60 dB, and it could also run on a '486. And Hamview used 16-bit code for the FFT routines. Today it is possible to find 32-bit FFT routines much more speedy than those. As for the sampling rate, I'm afraid the lowest speed modern sound cards can use is 5512.5 samples/sec. But decimation is always an option. 73, Alberto I2PHD From fgentges at mindspring.com Mon Jun 26 09:24:26 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:17 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> <39567D0C.7007FB45@tiscalinet.it> <3956ACE7.E7BB82CD@mindspring.com> Message-ID: <39574B7A.ABAAD4D2@mindspring.com> Frank Gentges wrote: > > Vittorio et al, > > I am hoping there is a free lunch out there in the compression schemes Snip snip > > My current thinking is to use a 750 Hz BFO frequency. Then filter the > audio data through a 600-900 Hz FIR bandpass filter to cut energy way > down, (60 db?) below 500 and above 1000 Hz. > > Initially sample this audio at 2000 samples per second to go into the > digital FIR filter. This is based on there being no energy above 1000 > Hz to avoid that alias. > > Then we have a 2000 samples per second rate of the output data stream of > the FIR. We take every other FIR output sample to achieve a 1000 sample > per second rate and throw the rest on the floor as they have no new > information. We would have a mirror image alias on the other side of > 500 Hz that would just be ignored or filtered out with a high pass > filter. > > That gets us 16000 bits per second if we transmit 16 bit samples. The > FIR filter may be a bit too much computation for a PC but I don't have > experience with that yet. > Snip Snip. Sorry to follow up on my previous post but a good nights sleep and some analog filter analysis.... Instead, use an analog active bandpass filter with a 600-900 passband and a 0-500 and a 1000-up 60 db stopband. Put the 300 Hz bandwidth CW output of the RX320 through this filter and use the 750 Hz BFO frequency. Sample the filter output at 1 kHz. This will probably require us to use a higher rate that is a multiple of 1 kHz and only select nth samples to make up 1 kHz. The analog active filter can be a 6 pole butterworth which is pretty simple. Given the relative simplicity of this filter, a switched capacitor filter may not make sense given that the clock will be in the low end of the LF band. We may want to try it just to see how bad the problem is. Enough for now, still looking for comments. Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From vdetomasi at tiscalinet.it Tue Jun 27 01:15:35 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:42:17 2003 Subject: [Lf] Re: lf digest, Vol 1 #147 - 3 msgs References: <200006261149.GAA22956@atanasoff.rf.org> Message-ID: <3957E416.BD0982E6@tiscalinet.it> Hi to all, I follow up the discussion about how to digitize and compress audio data on a narrow bandwidth. Frank is right when he says that one could sample at high frequency, and keep only one sample out of four (just to make an example). In this case you have no aliasing, because you are operating on a narrow band signal. There is however another way to do this. Let us say, as you described in your example, that you want only 200 Hz of bandwidth, say [800-1000] Hz. Instead of placing a bfo and a mixer between the filter and the ADC, simply use an ADC sampling at 400 Hz. You must check that the sample-and-hold before ADC can pass the desired bandwidth (I bet it will at such low frequency: this is probably not true on HF!), and that no anti-aliasing filters exist after the narrow band filter: in other words, leave the ADC free to generate plenty of aliasing! Now what happens is that the ADC samples correctly the frequency interval [0-200], wrap arounds [200-400] into [200-0] interval, aliases without wrap-around [400-600], then again wraps around [600-800] into [200-0], and eventually correctly aliases [800-1000] into [0-200]. Since the signal is bandpass, the aliased subbands give no contribution to the ADC conversion... The problem is how to implement this on a PC. I do not recommend using a modified sound blaster, because you cannot easily assure that this could be done on other cards (if you really want to experiment, and want to modify a sound card, either look for cards using AD1845 or similar, whose data sheets are easily available on Analog Devices web site, or use an external ADC connected to SPDIF input if available). Be careful also when specifying the sound card sampling rate. Infact Microsoft-Intel specifications about multimedia PC prescribe that *official* sampling frequencies for a so called "Multimedia level 2" sound card are 11,025 22,050 and 44,100 Hz with 16 bit of resolution. Other frequencies could be available on some cards, but you never know what happens with another card... If you want to use the sound card, sample at 11,025 Hz and put some DSP code in the PC. You have to band-pass the data with a FIR filter (40-60 taps will do a brick-wall filter), then resample using an appropriate method. As an alternative use the fast wavelet transform (AKA subband filtering) on input data, so you can easily extract the subband [689-1378] Hz readily undersampled by the fast wavelet transform. An alternative is building a dedicated ADC connected to the PC using serial (not recommended, UARTs have small buffers), parallel (used as EPP port, so you can take advantage of DMA transfer mode!), or USB ports. This solution has the advantage that it allows placing ADC close to the audio source, and leaving the PC far from the radio. I know that Cypress and Microchips recently released some microcontrollers with USB support, they could be a good platform to develop a dedicated ADC. As an alternative, I have somewhere a reference to an ADC that can be directly interconnected to USB bus: I'll look for the URL tomorrow. Abut data compression, one could consider A-law encoding (or maybe u-law encoding for people living in Europe :-) ) applied to each sample. Basically, you digitize data with 12 bits, then amplitude is compressed using an appropriate function into 8 bit. Dedicated ADCs exist (there is one in each ISDN telephone!), but A-law compression is easily done also with DSP methods. The small distorsion introduced by compression is probably negligible for our purposes. I suggest however not to waste time with audio compression methods, other than dynamic compression: I think that we cannot do better than the industries in this field (and I am not thinking about media industry, with MP3, MPEG2, and so on... oil industry for example spent a lot of money and efforts to develop sophisticated methods for data compression of noisy seismic data, with less than marginal results). vy 73 Vittorio IK2CZL > Today's Topics: > > 1. Re: Digitized Audio (Frank Gentges) > 2. Re: lf digest, Vol 1 #146 - 1 msg (Vittorio De Tomasi) > 3. Re: Re: lf digest, Vol 1 #146 - 1 msg (Frank Gentges) > > ------------------------------------------------------------------------ > < following text compressed to zero bytes lenght > -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "Wir muessen wissen; wir werden wissen" (David Hilbert) From fgentges at mindspring.com Mon Jun 26 22:13:49 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:18 2003 Subject: [Lf] Re: lf digest, Vol 1 #147 - 3 msgs References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> Message-ID: <3957FFCD.52318A91@mindspring.com> Vittorio and all, I have done some more analysis and conclude a six pole butterworth bandpass won't make the grade. A fine filter analysis program from Linear Technology called Filter CAD does a nice job on bandpass filters. That program indicates a 14 pole Elliptic bandpass will give a passband of 600-900 Hz and a 70 dB stopband below 500 Hz and above 1 kHz. The program suggests a switched capacitor Linear Technology filter chip type LTC-1068-200CG. If we conform to the multimedia level 2 and use use the 11025 Hz sample rate, we can take every 11th sample to yield a 1002.2 Hz sample rate. We probably cannot trust this rate to be too precise but it may be close enough. The Linear Technology filter chip only comes in surface mount, it needs two of these chips and they cost around $14 each from Digikey. It will require a handful of 1% resistors to tune it. I am concerned about the switching rate creating QRM but if we set it at 100 Khz I am not sure the Loran-C will be missed. We might also get some trash at 200, 300 and 400. The good part is once we build this filter, everything else should be simple off the shelf parts. If we stay with Multimedia level 2 we should not be too sensitive to different brands of sound cards, should we? Vittorio, you and Antonio have done wonders at using the standard Windows soundcard interface on Spectran. How does this sound to you? We can reduce this filter to a PC board so we can build some up without too much trouble if it looks like we can make this thing work with a dumpster grade computer, a dumpster grade 28.8 modem and an RX320, We also can explore the use of an active bandpass filter to implement a 14 pole Chebychev that might be cheaper to build. I want to look at that. Frank Vittorio De Tomasi wrote: > > Hi to all, > I follow up the discussion about how to digitize and compress audio data > on a narrow bandwidth. > > Frank is right when he says that one could sample at high frequency, and > keep only one sample out of four (just to make an example). In this case > you have no aliasing, because you are operating on a narrow band signal. > There is however another way to do this. > > Let us say, as you described in your example, that you want only 200 Hz > of bandwidth, say [800-1000] Hz. Instead of placing a bfo and a mixer > between the filter and the ADC, simply use an ADC sampling at 400 Hz. > You must check that the sample-and-hold before ADC can pass the desired > bandwidth (I bet it will at such low frequency: this is probably not > true on HF!), and that no anti-aliasing filters exist after the narrow > band filter: in other words, leave the ADC free to generate plenty of > aliasing! > > Now what happens is that the ADC samples correctly the frequency > interval [0-200], wrap arounds [200-400] into [200-0] interval, aliases > without wrap-around [400-600], then again wraps around [600-800] into > [200-0], and eventually correctly aliases [800-1000] into [0-200]. Since > the signal is bandpass, the aliased subbands give no contribution to the > ADC conversion... > > The problem is how to implement this on a PC. I do not recommend using a > modified sound blaster, because you cannot easily assure that this could > be done on other cards (if you really want to experiment, and want to > modify a sound card, either look for cards using AD1845 or similar, > whose data sheets are easily available on Analog Devices web site, or > use an external ADC connected to SPDIF input if available). Be careful > also when specifying the sound card sampling rate. Infact > Microsoft-Intel specifications about multimedia PC prescribe that > *official* sampling frequencies for a so called "Multimedia level 2" > sound card are 11,025 22,050 and 44,100 Hz with 16 bit of resolution. > Other frequencies could be available on some cards, but you never know > what happens with another card... > > If you want to use the sound card, sample at 11,025 Hz and put some DSP > code in the PC. You have to band-pass the data with a FIR filter (40-60 > taps will do a brick-wall filter), then resample using an appropriate > method. As an alternative use the fast wavelet transform (AKA subband > filtering) on input data, so you can easily extract the subband > [689-1378] Hz readily undersampled by the fast wavelet transform. > > An alternative is building a dedicated ADC connected to the PC using > serial (not recommended, UARTs have small buffers), parallel (used as > EPP port, so you can take advantage of DMA transfer mode!), or USB > ports. This solution has the advantage that it allows placing ADC close > to the audio source, and leaving the PC far from the radio. > > I know that Cypress and Microchips recently released some > microcontrollers with USB support, they could be a good platform to > develop a dedicated ADC. As an alternative, I have somewhere a reference > to an ADC that can be directly interconnected to USB bus: I'll look for > the URL tomorrow. > > Abut data compression, one could consider A-law encoding (or maybe u-law > encoding for people living in Europe :-) ) applied to each sample. > Basically, you digitize data with 12 bits, then amplitude is compressed > using an appropriate function into 8 bit. Dedicated ADCs exist (there is > one in each ISDN telephone!), but A-law compression is easily done also > with DSP methods. The small distorsion introduced by compression is > probably negligible for our purposes. > > I suggest however not to waste time with audio compression methods, > other than dynamic compression: I think that we cannot do better than > the industries in this field (and I am not thinking about media > industry, with MP3, MPEG2, and so on... oil industry for example spent a > lot of money and efforts to develop sophisticated methods for data > compression of noisy seismic data, with less than marginal results). > > vy 73 > > Vittorio IK2CZL > > > Today's Topics: > > > > 1. Re: Digitized Audio (Frank Gentges) > > 2. Re: lf digest, Vol 1 #146 - 1 msg (Vittorio De Tomasi) > > 3. Re: Re: lf digest, Vol 1 #146 - 1 msg (Frank Gentges) > > > > ------------------------------------------------------------------------ > > > > < following text compressed to zero bytes lenght > > > -- > ************************************************************************* > Vittorio De Tomasi ik2czl@amsat.org > Home page: http://space.tin.it/scienza/vdetomas > My DSP page: http://www.freeyellow.com/members/padan > > "Wir muessen wissen; wir werden wissen" (David Hilbert) > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From tfox at erols.com Mon Jun 26 22:20:00 2000 From: tfox at erols.com (Terry Fox) Date: Thu Jul 3 13:42:18 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> <39567D0C.7007FB45@tiscalinet.it> Message-ID: <3958013F.1AC98348@erols.com> As we talked about at tacos last Saturday, you will probably need a lossless compression system. They are generally limited to a 2:1 compression ratio at best. Any other system will throw away data that is needed. As an alternative, we can reduce the samples in frequency. Since you want a narrow bandwidth result, if you resample at a lower frequency, you can drop the audio frequency range to close to the bandwidth. This gives the same frequency range (remembering Nyquist), but much fewer samples. For example, a 200Hz bandwidth centered around 1KHz would require at least a 2.2KHz sample rate. Moving the samples down to 300Hz would only require a 800 Hz sample rate (I think). Now, apply a lossless compression of about 2:1. That would result in 400 samples per second. If those samples were reduced from 16 bits to 12 or even 8, then more data can be sent. While frequency compression may lose too much data, a non-linear amplitude compression method may be successful. I think we can achieve some compression on the audio data without losing data integrity. If we can achieve a low enough data rate, we can also use radios to connect to remote receivers in addition to the Internet. Sending the audio as data would be much better than just sending the audio itself. It would not be distorted by the retransmission method. Terry Vittorio De Tomasi wrote: > Hi Frank and the list, > > here are my opinions on your problem: > > if you want to digitize a receiver outbut and still be able to detect > very faint signals buried under the noise, forget about audio > compression, like MP3, RA, GSM, and so on! > > The reason is quite simple: compression (as well as denoising!) is done > designing a suitable mathematical model that is fitted to the signal. > Best fit is obtained by minimizing the energy of the difference signal > (input minus modeled signal): computationally efficient methods exist to > compute the signal model that fits at its best the incoming data. The > difference between input signal and the model is simply discarded, and > the transmitted information is the one needed to build up the model. > > MP3 adds to the best fitting process a psychoacoustic model: suppose > that you listen to a 1000 Hz signal. Now add a 1500 Hz signal, and > increase its amplitude until you hear it. Turn it off, and do the same > for a tone at 1010 Hz: you will need quite a larger amount of signal to > become aware that the tone at 1010 Hz is played with the steady 1000 Hz > tone. MP3 encoders recognize the presence of tone pairs, and apply > dynamic compression, i.e. they use a coarser signal quantization when a > weak tone is close to a strong one. Imagine this kind of processing > applied to VLF signals.... > > The best compression to do is Nyquist compression: if you have B Hz of > bandwidth, sample them at a rate equal to 2B (maybe a little more, just > to avoid aliasing), and use a suitable number of bits to get the needed > dynamic range. So for a data stream of 16 kbit/s, you can transmit 500 > Hz of bandwidth with 16 bit (i.e. about 96 dB of dynamic range, not > bad...). > > Amplitude data can be encoded into the data stream replacing say a > sample every 16k, so getting an amplitude measurement every second. The > "lost" sample will be silently ignored also by the most sophisticated > DSP engine. > > However there is a more efficient method: why don't you simply transmit > the frequency spectrum ?!? I suppose you have a two way data channel, so > you can think of sending commands to the "DSP server" in order to > transmit you the desired frequency slice. What do you think about this > ?!? > > vy 73 > > Vittorio IK2CZL > > > Today's Topics: > > > > 1. Digitized Audio (Frank Gentges) > > > > ------------------------------------------------------------------------ > > > > Subject: [Lf] Digitized Audio > > Date: Sat, 24 Jun 2000 20:02:20 -0400 > > From: Frank Gentges > > Organization: K0BRA > > To: LF@AMRAD.org, tacos@AMRAD.org > > > > Hi, > > > > At tacos today I mentioned that I was looking for a good method to > > digitize the 300 Hz bandwidth CW output of the RX320 to transmit > > remotely at something around 16 kilobits per second. I have looked at a > > few available options in WIN98 and at Xing's MP3 encoder. > > > > I would like to find the best option that will provide a good > > spectrogram with Spectran at the remote end. > > > > If I were to set the RX320 BFO for a 250 Hz, then the band should extend > > from 100 Hz to 100 + 300 = 400 Hz. But, the RX320 at 300 Hz bandwidth > > has quite a bit of energy beyond 500 Hz and you can hear the beat note > > come through zero which means significant artifacts could creep into the > > spectrogram. Simply put, the 300 Hz bandwidth has quite a bit of > > transition band beyond the 300 Hz edges before the signal is far enough > > down to ignore. > > > > One option would be to set the BFO for a 1 kHz center frequency like we > > do now for driving Spectran. The signal could be digitized and further > > filtered digitally in real-time yielding a 16 kilobit per second > > stream. A reverse process could then be used on the remote end. If > > this could have limited processing load it could be done in the PC. > > While we are at it we need to multiplex into the stream the RX320 signal > > strength data, but lets not get ahead of ourselves. > > > > Another option would be to use a streaming audio process like MP3 or the > > like to encode the audio. MP3 is an open specification and we should be > > able to use it freely. > > > > RealAudio might be an option but it is proprietary and does not seem to > > have a low rate option. Neither do we know the impact on Spectran of > > its artifacts. It would be nice to know how much we might be missing > > here. > > > > In the end, I would like to be able to put a remote RX320 and computer > > anywhere in the world and with a modem based internet (or modem direct) > > connection, be able to listen to the LF band. > > > > Any thoughts? Even better, any volunteers to work on this problem so we > > can put your solution in our handbook? > > > > Frank > > -- > > Frank Gentges > > K0BRA, ex AK4R, W3FGL > > Check out our LF web page at > > > > ------------------------------------------------------------------------ > > _______________________________________________ > > lf mailing list > > lf@amrad.org > > http://www.amrad.org/mailman/listinfo/lf > > -- > ************************************************************************* > Vittorio De Tomasi ik2czl@amsat.org > Home page: http://space.tin.it/scienza/vdetomas > My DSP page: http://www.freeyellow.com/members/padan > > "Wir muessen wissen; wir werden wissen" (David Hilbert) > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf From fgentges at mindspring.com Tue Jun 27 09:57:06 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:18 2003 Subject: [Lf] Symposium Proceedings References: <20000622.230932.-73253.1.riese-k3djc@juno.com> Message-ID: <3958A4A2.A10098F7@mindspring.com> Bob and LFers, You inquired about the availability of the Symposium Proceedings. They are available as follows: Symposium Proceedings: $12 (cover price) + 2 (mailing) = $14 for the proceedings (mailed) or $12 in person. The proceedings contain a number of new articles on things AMRAD members are doing including APRS and LF. AMRAD Pin: $2 (cost rounded upward) + 1 (mailing) = $3 for AMRAD pin (mailed or $2 in person. The AMRAD pin is a nice little pin with the AMRAD logo on it. Mail to: AMRAD P.O. Drawer 6148 McLean VA 22106-6148 Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From vdetomasi at tiscalinet.it Tue Jun 27 18:56:44 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:42:19 2003 Subject: [Lf] Re: lf digest, Vol 1 #147 - 3 msgs References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> <3957FFCD.52318A91@mindspring.com> Message-ID: <3958DCCB.CA7BBFDF@tiscalinet.it> Frank, I think that 14 USD are too much for a bandpass filter: a DSP solution is really a free lunch! You need about 2N(log2(2N) + 1) operations to do the whole filtering process with FFT. Let us say you sample at 11,025 samples/s, and you use a buffer of 1024 samples. It follows you need about 25,000 operations for each buffer to do the filtering, i.e. you can go real time with a system that is able to deliver 250 kFLOPs (if I'm not wrong). Since 1002.2 Hz is a bit odd sampling rate, you can interpolate down to 1000 Hz using nearest-neighbour interpolation (this usually results in some THD, but it needs only a look-up operation) or linear interpolation spending about 3 FLOP for each emitted sample. However I have a question: how do you think to transmit data ? Remember that if you send 16 bit samples, you need to find a way to synch them, otherwise you could put together the wrong sequence on the other side... probably it is better to use some transport layer like TCP/IP: anybody there willing to hack KA9Q code ?!? Vittorio -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "Wir muessen wissen; wir werden wissen" (David Hilbert) From vdetomasi at tiscalinet.it Tue Jun 27 20:03:37 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:42:19 2003 Subject: [Lf] Re: lf digest, Vol 1 #146 - 1 msg References: <200006251158.GAA15589@atanasoff.rf.org> <39567D0C.7007FB45@tiscalinet.it> <3958013F.1AC98348@erols.com> Message-ID: <3958EC79.1BECD21D@tiscalinet.it> Terry Fox wrote: > > As we talked about at tacos last Saturday, you will probably need a lossless > compression system. They are generally limited to a 2:1 compression ratio at > best. Any other system will throw away data that is needed. Terry, this probably does not work: if your input signal is close to white noise (and VLF signals are very similar to noise!), you cannot find a lossless compression scheme, because there is no way to reduce the data entropy using a different coding system. > As an alternative, > we can reduce the samples in frequency. Since you want a narrow bandwidth > result, if you resample at a lower frequency, you can drop the audio frequency > range to close to the bandwidth. This gives the same frequency range > (remembering Nyquist), but much fewer samples. > > For example, a 200Hz bandwidth centered around 1KHz would require at least a > 2.2KHz sample rate. Moving the samples down to 300Hz would only require a 800 > Hz sample rate (I think). > Not exactly. If you have a signal with a bandwidth of B hertz, whose bandwidth extends from Bo to Bo + B hertz, you can sample it using 2B samples/second without introducing aliasing (you actually sample the analytic representation of the signal). But to reconstruct the signal as the original one, you need to filter the sampled sequence with a suitable reconstruction filter. That reconstruction filter is a bandpass with bandwidth [Bo, Bo + B], where Bo is the lowest frequency contained in your signal. Now put Bo = 0, and the bandpass filter becomes...a lowpass, and you get the good old Nyquist theorem described in textbooks. If you have the famous Oppenheim Shaefer textbook on DSP at hand, sampling methods for bandpass signals are described in the chapter about Hilbert transform (and not all DSP textbooks unfortunately tell this...). > Now, apply a lossless compression of about 2:1. That would result in 400 > samples per second. If those samples were reduced from 16 bits to 12 or even 8, > then more data can be sent. While frequency compression may lose too much data, > a non-linear amplitude compression method may be successful. > Yeah, it should be successful, and it is where we should experiment with... we could also think about moving amplitude compression into the AGC stage, using a DSP-controlled AGC system. Any idea ?!? > I think we can achieve some compression on the audio data without losing data > integrity. If we can achieve a low enough data rate, we can also use radios to > connect to remote receivers in addition to the Internet. Sending the audio as > data would be much better than just sending the audio itself. It would not be > distorted by the retransmission method. > Terry > We should use this method also with our FM repeaters: will we have one day an ham-radio digital communication system similar to Ericsson's TETRA ?!? We could save a lot of bandwidth, and use the saved radio spectrum for something more interesting... vy 73 Vittorio -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "Wir muessen wissen; wir werden wissen" (David Hilbert) From fgentges at mindspring.com Tue Jun 27 21:06:04 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:19 2003 Subject: [Lf] LF Remote Receiver References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> <3957FFCD.52318A91@mindspring.com> <3958DCCB.CA7BBFDF@tiscalinet.it> Message-ID: <3959416C.57619300@mindspring.com> Vittorio, Your numbers look attractive. The filter seems to be growing here to 2 chips and 54 1% resistors. If we can do it in the processor for free that may be a key advantage. You are suggesting an FFT, a removal of unwanted spectral lines and then an inverse FFT if I understand. I am note sure a 1000 Hz vs a 1002.2 Hz sample rate is an issue as long as you use it on both ends. Since we will use a sound card on both ends we can stuff the sample into the D/A 11 times at the 11025 rate. I am thinking about transmitting data both ways via a PPP I/P type connection to make an internet connection simple. We are seeing a lot of DSL installations now with PPP over Ethernet so it looks like PPP will be around a while. We can also use a direct modem connection and PPP I/P may be the best way to go there also. We need to carry the RX320 control commands from the base station to the remote. That is a 1200 bit per second link and usually is idle unless the receiver is being tuned or adjusted. We have a small amount of signal strength data to come from the remote along with the digitized sound. The third method would use an RF link using VHF FM in place of the modem. The remote transmitter would come up on the air in response to a command from the base station. In addition to the digitized narrowband signal, we could digitize a block of wideband stuff and transfer it in non real time for playback. This could let us listen to a sample of the European LF broadcast signals. We have had armchair copy at times at Nags Head on them in the winter and spring. I want to redirect the RX320 data port at the base station so the RX320 control may be via any of the RX320 control programs. The base station will most likely be running a flavor of the Windows operating system in order to run these programs. The remote station will run Linux so we don't have to drive down and clear blue screens of death and reboot every few days. The remote should run for months without attention once we get it debugged. My local linux machine has now been up for 217 day without a reboot. With a standard internet connection we can place these remotes anywhere in the world where we can get a decent internet connection. A 28.8 connection should do fine. There is nothing keeping us from using this on MW or HF either. N2JEU has an RX320 web radio but it uses audio compression and control is limited although many can listen at the same time. We are looking for something a bit different. Your comments are providing some good insight and are most helpful. Frank Vittorio De Tomasi wrote: > > Frank, > > I think that 14 USD are too much for a bandpass filter: a DSP solution > is really a free lunch! > You need about 2N(log2(2N) + 1) operations to do the whole filtering > process with FFT. Let us say you sample at 11,025 samples/s, and you use > a buffer of 1024 samples. It follows you need about 25,000 operations > for each buffer to do the filtering, i.e. you can go real time with a > system that is able to deliver 250 kFLOPs (if I'm not wrong). > > Since 1002.2 Hz is a bit odd sampling rate, you can interpolate down to > 1000 Hz using nearest-neighbour interpolation (this usually results in > some THD, but it needs only a look-up operation) or linear interpolation > spending about 3 FLOP for each emitted sample. > > However I have a question: how do you think to transmit data ? Remember > that if you send 16 bit samples, you need to find a way to synch them, > otherwise you could put together the wrong sequence on the other side... > probably it is better to use some transport layer like TCP/IP: anybody > there willing to hack KA9Q code ?!? > > Vittorio > -- > ************************************************************************* > Vittorio De Tomasi ik2czl@amsat.org > Home page: http://space.tin.it/scienza/vdetomas > My DSP page: http://www.freeyellow.com/members/padan > > "Wir muessen wissen; wir werden wissen" (David Hilbert) -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From tfox at erols.com Tue Jun 27 21:58:18 2000 From: tfox at erols.com (Terry Fox) Date: Thu Jul 3 13:42:20 2003 Subject: [Lf] LF Remote Receiver References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> <3957FFCD.52318A91@mindspring.com> <3958DCCB.CA7BBFDF@tiscalinet.it> <3959416C.57619300@mindspring.com> Message-ID: <39594DA9.3DFBBFD@erols.com> Frank: This morning I was thinking the very same thing, sounds good. Here is another idea. How about using a low-end Pentium (I can probably supply it). Rather than using a hardware filter, how about implementing a larger FIR filter on the digitized audio from the sound card. Then take the resulting digital data and sub-sample it. I think you can sub-sample it because the actual signal will be narrower than say 1kHz where the filter is. The resulting data can be compressed and sent out the PC as digitized audio, but NOT the actual FFT data. The data would be received and processed at the receive end. The reason for the FIR filter is that you should be able to build a very-flat but also very steep-skirted filter with a many-tap FIR. The Pentium should be able to handle an 80-tap or so FIR. Vittorio, I sort of agree with your earlier comments about digitized LF audio having significant digitized noise and therefore reducing a lossless compression scheme's effectiveness. We can probably still get some efficiency with run-length or other system. I was most concerned about NOT using any lossy compression, as that would probably destroy enough of the signal before you got a chance to perform any real calculations on it. Frank Gentges wrote: > Vittorio, > > Your numbers look attractive. The filter seems to be growing here to 2 > chips and 54 1% resistors. If we can do it in the processor for free > that may be a key advantage. You are suggesting an FFT, a removal of > unwanted spectral lines and then an inverse FFT if I understand. I am > note sure a 1000 Hz vs a 1002.2 Hz sample rate is an issue as long as > you use it on both ends. Since we will use a sound card on both ends we > can stuff the sample into the D/A 11 times at the 11025 rate. > > I am thinking about transmitting data both ways via a PPP I/P type > connection to make an internet connection simple. We are seeing a lot > of DSL installations now with PPP over Ethernet so it looks like PPP > will be around a while. > > We can also use a direct modem connection and PPP I/P may be the best > way to go there also. We need to carry the RX320 control commands from > the base station to the remote. That is a 1200 bit per second link and > usually is idle unless the receiver is being tuned or adjusted. We have > a small amount of signal strength data to come from the remote along > with the digitized sound. > > The third method would use an RF link using VHF FM in place of the > modem. The remote transmitter would come up on the air in response to a > command from the base station. > > In addition to the digitized narrowband signal, we could digitize a > block of wideband stuff and transfer it in non real time for playback. > This could let us listen to a sample of the European LF broadcast > signals. We have had armchair copy at times at Nags Head on them in the > winter and spring. > > I want to redirect the RX320 data port at the base station so the RX320 > control may be via any of the RX320 control programs. The base station > will most likely be running a flavor of the Windows operating system in > order to run these programs. > > The remote station will run Linux so we don't have to drive down and > clear blue screens of death and reboot every few days. The remote > should run for months without attention once we get it debugged. My > local linux machine has now been up for 217 day without a reboot. > > With a standard internet connection we can place these remotes anywhere > in the world where we can get a decent internet connection. A 28.8 > connection should do fine. > > There is nothing keeping us from using this on MW or HF either. N2JEU > has an RX320 web radio but it uses audio compression and control is > limited although many can listen at the same time. We are looking for > something a bit different. > > Your comments are providing some good insight and are most helpful. > > Frank > > Vittorio De Tomasi wrote: > > > > Frank, > > > > I think that 14 USD are too much for a bandpass filter: a DSP solution > > is really a free lunch! > > You need about 2N(log2(2N) + 1) operations to do the whole filtering > > process with FFT. Let us say you sample at 11,025 samples/s, and you use > > a buffer of 1024 samples. It follows you need about 25,000 operations > > for each buffer to do the filtering, i.e. you can go real time with a > > system that is able to deliver 250 kFLOPs (if I'm not wrong). > > > > Since 1002.2 Hz is a bit odd sampling rate, you can interpolate down to > > 1000 Hz using nearest-neighbour interpolation (this usually results in > > some THD, but it needs only a look-up operation) or linear interpolation > > spending about 3 FLOP for each emitted sample. > > > > However I have a question: how do you think to transmit data ? Remember > > that if you send 16 bit samples, you need to find a way to synch them, > > otherwise you could put together the wrong sequence on the other side... > > probably it is better to use some transport layer like TCP/IP: anybody > > there willing to hack KA9Q code ?!? > > > > Vittorio > > -- > > ************************************************************************* > > Vittorio De Tomasi ik2czl@amsat.org > > Home page: http://space.tin.it/scienza/vdetomas > > My DSP page: http://www.freeyellow.com/members/padan > > > > "Wir muessen wissen; wir werden wissen" (David Hilbert) > > -- > Frank Gentges > K0BRA, ex AK4R, W3FGL > Check out our LF web page at > > _______________________________________________ > lf mailing list > lf@amrad.org > http://www.amrad.org/mailman/listinfo/lf From aa4hs at amrad.org Wed Jun 28 00:35:26 2000 From: aa4hs at amrad.org (Maitland Bottoms) Date: Thu Jul 3 13:42:20 2003 Subject: [Lf] LF Remote Receiver In-Reply-To: <39594DA9.3DFBBFD@erols.com> References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> <3957FFCD.52318A91@mindspring.com> <3958DCCB.CA7BBFDF@tiscalinet.it> <3959416C.57619300@mindspring.com> <39594DA9.3DFBBFD@erols.com> Message-ID: <14681.29310.831553.306936@airborne.nrl.navy.mil> There are many days that I listen to my radio (located at home) while I am at work. Having DSL helps, no doubt. Here's a list of enabling technologies I use: - Icom PCR-1000 - Debian software packages: - pcrd: command line pcr-1000 control - tkpcr: GUI for pcr-1000 - speak-freely: internet audio with various modes - multimon: software demodulation Note that for building software filters, Phil Karn has one referenced from http://people.qualcomm.com/karn/dsp.html that is optimized for pentiums. That technology is folded into the multimon application. I see a remote receive computer doing quite a bit of computation, so that the remote operator can get a high-level overview of signal spectrums and levels without the need to transmit real-time values. -Maitland From fgentges at mindspring.com Wed Jun 28 00:33:22 2000 From: fgentges at mindspring.com (Frank Gentges) Date: Thu Jul 3 13:42:21 2003 Subject: [Lf] BeaconSee Message-ID: <39597202.6D8FD813@mindspring.com> LFers, Interesting beacon concept at . Maybe we could adapt to LF. Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at From vdetomasi at tiscalinet.it Wed Jun 28 21:51:37 2000 From: vdetomasi at tiscalinet.it (Vittorio De Tomasi) Date: Thu Jul 3 13:42:21 2003 Subject: [Lf] Re: LF Remote Receiver References: <200006261149.GAA22956@atanasoff.rf.org> <3957E416.BD0982E6@tiscalinet.it> <3957FFCD.52318A91@mindspring.com> <3958DCCB.CA7BBFDF@tiscalinet.it> <3959416C.57619300@mindspring.com> Message-ID: <395A5749.5CA234@tiscalinet.it> Hi Frank, Frank Gentges wrote: > > Vittorio, > > Your numbers look attractive. The filter seems to be growing here to 2 > chips and 54 1% resistors. If we can do it in the processor for free > that may be a key advantage. Since you want to throw away chips and resistors and use dsp, may I suggest you to throw away also your RX320 receiver ?!? I'm not joking: put together a tight band pass filter at 137 kHz, a SBL-1 mixer, a local oscillator somewhere around 130 kHz, a post amplifier, and extract from this an i.f. frequency at 7 kHz, so that we can detect radio signals directly with a sound card and a dsp software implementing a ssb detector! By the way, Spectran will work as a poor man's substitute for a dsp receiver: simply zoom on the i.f. region, and you will see what you are receiving. With the 16 bit of resolution available from a sound card, we get about 96 dB of dynamic range for this "receiver", not bad but probably not enough. However 24 bit sound card are becoming available (also if they are not cheap), and this is around 140 dB of dynamic range... There is no need for a pll/dss conversion oscillator, since tuning can be easily done in dsp (at least within a certain frequency range). Anything else to throw away ?!? vy 73 Vittorio -- ************************************************************************* Vittorio De Tomasi ik2czl@amsat.org Home page: http://space.tin.it/scienza/vdetomas My DSP page: http://www.freeyellow.com/members/padan "Wir muessen wissen; wir werden wissen" (David Hilbert) From esanders at erols.com Fri Jun 30 00:18:17 2000 From: esanders at erols.com (Nan and Sandy Sanders) Date: Thu Jul 3 13:42:21 2003 Subject: [Lf] Directions to SAQ party Message-ID: <01BFE220.71C48A80.esanders@erols.com> The party will be at 38 59 06 N 078 00 00 W. Take I66 West to the Front Royal / Linden exit left at bottom of ramp to Rt. 55 left on Rt 55 to Freezeland rd follow Freezeland rd to the top be sure to take the switch back ( almost 180 degrees) not go straight. Go past the end of the pavement and past the radio towers. You will be on a fairly wide dirt road. At some point past the towers (I have not figured mileage) the nice wide dirt road will make a hard left. Do not turn. Go straight on to the narrow dirt road. If you find your self going down hill you probably turned left. We will be on the right in a parking for the G Richard Thompson Wildlife Management Area that has a good view to the East. There are several lots but this one has the most open area around it. I will try to get there an hour or two before sunset to string wire. Final plans will be worked out a Tacos. Sandy From akestelo at bellatlantic.net Fri Jun 30 10:18:31 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:21 2003 Subject: [Lf] LORAN C reference question] Message-ID: <395C9E27.5E254495@bellatlantic.net> Stewart Nelson wrote: > Hi all, > > IMO, WWVB is not a good source for a frequency reference, unless > you are close enough to Fort Collins to consistently receive > a predominantly surface wave signal. Otherwise, the QSB associated > with skywave will occasionally (typically once per night) create > a signal which dips in amplitude and recovers with a phase shift of > approximately 180 degrees. When this happens, it is hard to tell > if you have gained or lost half a cycle. > > As a result, you can't expect accuracy/stability better than about > 1E-9, even if your LO is oven controlled and you are using a long > time constant. > > With LORAN or GPS, it's easy to do a factor of 100 better. > > WWVB is not the best way to tell time, either. > It is difficult to precisely measure transitions of the > low frequency ASK. You are lucky if you can synchronize > within a few hundred microseconds. With LORAN or GPS, > it is easy to get within a few hundred nanoseconds, and a > good system can average over several hours and achieve > accuracy of a few nanoseconds. > > 73, > Stewart KK7KA From akestelo at bellatlantic.net Fri Jun 30 15:41:48 2000 From: akestelo at bellatlantic.net (Andre' Kesteloot) Date: Thu Jul 3 13:42:21 2003 Subject: [Lf] AIR MILES CALCULATOR Message-ID: <395CE9EB.55C4143C@bellatlantic.net> les@highnoonfilm.com wrote: > Found a very useful web site that will calculate air miles between any two > points > in the world just by typing in the names of the cities. It's at: > > http://www.indo.com/distance/ > > It also provides Lat/Long, elevation, etc. It even gives beam headings so that > you can point those loops or beverages right at them. Very nice! > [...] > Hope someone else finds this useful. > > Les Rayburn, KT4OZ > XMGR 187.500Khz.