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Re: LF: 73kHz

To: <[email protected]>
Subject: Re: LF: 73kHz
From: "James Moritz" <[email protected]>
Date: Tue, 18 Oct 2011 18:34:08 +0100
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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


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