[Fwd: LF: PSK31]

Andre Kesteloot akestelo@bellatlantic.net
Thu, 23 Apr 1998 17:47:55 -0400

Peter Martinez wrote:

> >From Peter Martinez G3PLX Kendal Cumbria.
> A bit more on PSK31 to amplify Andy's comments.
> Andy refers to PSK31 as a "data" mode, but I prefer to call it an
> "RTTY" mode, since what is exchanged is text typed on a keyboard
> at one end and displayed on a screen at the other. It's ideal for this,
> with two or more stations all able to copy each other, break-in, listen
> on the side and transmit at random, and is not optimised for
> automated exchange of files or data. On HF, my philosophy for
> PSK31 is to try to restore the lost art of one-to-one QSOs and
> counter the trend for "data" modes to be used only between
> machines.
> PSK31 is actually +/-15Hz at 60dB down, that is, about 31Hz wide,
> but that's still very much narrower than any other mode. This
> includes hand-sent CW, which is usually much wider than it needs
> to be, and is actually quite tiring to read if you filter it to it's
> theoretical minimum bandwidth.
> As well as running on the 56002EVM kit, PSK31 can be run on a
> TMS320C50 kit, which is about the same price. In both cases you
> plug the kit into the serial port of the PC, and connect audio output
> from the kit to the Mic socket of the tx and receiver audio into the
> kit, then run the associated program on the PC. Hopefully it should
> become availble to run on other hardware setups soon. Last night I
> worked the first station running PSK31 on a standard sound-card,
> but it will be a few months before it is generally available, as the
> author has so far written it for a rather specialised operating system
> which is not MSDOS on Windows. There is also the possibility for
> doing PSK modulation/demodulation in good old hardware. For VLF,
> this could mean that the receive side is a PLL chip working from the
> receiver audio, and the transmit side is a balanced modulator (or
> perhaps a pair of them), either fed with a carrier at RF for direct
> generation of the 136 kHz signal or running at audio for SSB mode.
> In either case it does help to keep the bandwidth down if the
> transmitter is linear, but even with a Class-C PA the readability does
> not deteriorate, but it would have keyclick sidebands 6dB louder
> than a 40wpm CW signal. If anyone would like to try experimenting
> with hardware for reception or transmission of PSK, let me know and
> I can help with ideas and test programs.
> 73
> Peter G3PLX