LF: Fwd: News from Harry, G3MFW]

Andre Kesteloot akestelo@bellatlantic.net
Wed, 14 Jan 1998 19:37:17 -0500

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Date: Wed, 14 Jan 1998 20:20:41 +0000
To: rsgb_lf_group@blacksheep.org
From: John W Gould <g3wkl@pagnell.demon.co.uk>
Subject: LF: Fwd: News from Harry, G3MFW
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Dear John,
Happy New Year! I have at last completed my 2 turn loop, delayed first
by a bad back, then impossible weather. The loop is vertical in the E-W
plane and goes right over the house. It is made of 40way telephone cable
with all turns in parallel. R = 0.18 ohms, L =  175 microhenries,
resonating C = 28000pf  polypropylene, Q =  72. It is fed  between the
two turns with my ancient valve amplifier with two KT66s in the PA
running at 500v giving about 56 watts dc input.  Oscillator is crystal
and divider design by Andy, giving 72.1 Khz. (VFO also available).
Keying by my callsign cut in a rotating disc with a hacksaw, via a
transistor and relay which switches the valve amp input between earth
and the divider. Amp input resistance is 1 meg, and divider is loaded
with 300 ohms, so no disturbance of phase of oscillator during keying. I
get 5 amps RF in the loop, measured with thermocouple RF ammeter, and
about  500v across the 2 turns. I also have Andys excellent slow morse
computer program, so can use this if required.

        I received the conventional (very bad!) morse in Truro 20Km to
the west, using a 31 turn shielded loop feeding a Datong VLF converter,
feeding my old Yaesu FR 101 with 600 Khz bandwidth, in turn feeding an
old Datong analogue filter with 100 Hz bandwidth. The only way I could
find the signal amongst the deafening noise was by using my portable
Xtal oscillator, also tuned to 72.1 Khz, as a marker. There were 11KV
overhead wires everywhere. I received nothing at all with a wire
antenna, or the loop not carefully tuned and interference nulled out. I
plan further tests to the east (over the sea), and am building a 400watt
valve amplifier.

        I realise these results are very poor, but they might encourage
other amateurs who are impecunious pensioners like me with no formal
training in electronics. Anyway I have had lots of fun, and would be
delighted to put out test signals on telephone request. I need two
minutes notice for horrible morse, but an hour or so to carry my
computer into the garage for professional slow morse!
Harry, St. Austell, G3MFW phone 01726 73608

12th Jan 98

John Gould, G3WKL