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Date: Tue, 18 Oct 2011 19:08:46 +0100
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From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: 73kHz
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The very first amateur use of QRSS (we used the term SLOWCW)    :

http://www.g4jnt.com/DownLoad/G4JNT008.BMP   as received by G3PLX at a
distance of 393km.

My transmission, which was about 1mW ERP, was generated with 160 Watts
of RF from a couple of Maplin Mosfet audio amps in bridge driving a 7m
high Tee antenna.      Peter was receiving in a bandwidth, as far as I
recall, of something like 40mHz and my transmitted dot length was 30
seconds. What would now be referred to as QRSS30.  We tried different
speeds each night but this was one of the best results

Numbers along the bottom are UTC hours.   This was before the days of
soundcard based DSP.   Peter used a Motorola 56002 DSP card to
digitise the signal from an SSB receiver, decimate the sampling rate
and send the results to a PC via the serial port (a while before the
USB interface was in use, too).   Custom software did the FFT and
produced the plots.

It took another year or two before soundcard based DSP was in
widespread use, mainly due to a Richard Horne's, GRAM software.
Richard was a bird watcher, and wrote GRAM for analysing birdsong, but
it was quickly adapted, along with a few mods added by Richard. for
Amateur SlowCW use.

Andy
g4jnt



On 18 October 2011 18:34, James Moritz <james.moritz@btopenworld.com> wrote=
:
> Dear Stefan, LF Group,
>
> 73kHz reception was a problem in the UK because of an FSK utility located=
 at
> Rugby in the middle of the band, which had strong noise sidebands that
> created QRM across the whole band. It used to shut down for maintenance f=
or
> an hour or two each month - then there would be a rush of UK stations try=
ing
> to work each other in CW. It also lead to the funny situation that the
> UK-only 73kHz signals could often be received better by stations in mainl=
and
> Europe, and there were quite a few cross-band 73k - 136k QSOs. Radiating =
a
> signal on 73k had the same problems as 136k but more so, and corona, melt=
ed
> insulators etc., tended to be rather common! But quite a few stations
> managed to transmit reasonable signals.
>
> Once you managed to radiate a signal, it would go a long way, with extend=
ed
> ground wave range compared to 136k, even with rather low ERP. Some QRSS
> transatlantic signals were received. I think 73kHz was perhaps the first
> place QRSS was used, with early experiments between G4JNT and G3PLX. =A0I
> recall the last 73kHz QSO was between G3XDV and G3LDO, these stations als=
o
> had the first 2-way QSO on the band. Perversely, the withdrawal of the 73=
k
> band happened at about the same time the Rugby FSK utility was
> decommissioned. Nowadays, this part of the spectrum is remarkably quiet..=
.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>