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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4E99EA7C.5080200@iup.uni-heidelberg.de> <CAO19VgMEjRxDTsuSveG_6nmD2gcMnfYGzGvWULD4RE=U9eDtkA@mail.gmail.com> <4E9C2CB9.3040303@iup.uni-heidelberg.de> <4E9C71B1.9010306@legal-medicine.de> <4E9C74DE.5090407@iup.uni-heidelberg.de> <00fc01cc8d21$dc5fba00$4001a8c0@lark> <4E9D9CA9.5050604@iup.uni-heidelberg.de>
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Date: Tue, 18 Oct 2011 18:34:08 +0100
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Subject: Re: LF: 73kHz
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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 for 
an hour or two each month - then there would be a rush of UK stations trying 
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 mainland 
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, melted 
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 extended 
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.  I 
recall the last 73kHz QSO was between G3XDV and G3LDO, these stations also 
had the first 2-way QSO on the band. Perversely, the withdrawal of the 73k 
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