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Message-ID: <5.1.0.14.0.20020206102338.00a71bf0@gemini.herts.ac.uk>
Date: Wed, 06 Feb 2002 12:12:11 +0000
To: rsgb_lf_group@blacksheep.org
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Subject: Re: LF: PSK31 Tests on Tuesday evening
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Dear LF Group,

Thanks to Wolf, Geri and Andy for the 4 - way PSK31 QSO last night, and 
also for all the listener reports. G4JNT and DF0WD/DL4YHF were almost 
perfect copy throughout, with only an occasional corrupted character due to 
static crashes. DK8KW's signal was subject to a slow, deep fade that lasted 
the duration of the QSO - frustratingly, Geri's signal was quite good copy 
in his QSO with Wolf before I started up, and the signal level was 
improving again at the end of the QSO, so I was getting 30 - 40% good copy 
at the end, but in-between Geri was at times inaudible and barely visible 
on the spectrogram. When sending the test signals later on, I could see 
weak "tracks" of an FSK signal on the screen around 137.4 (I think these 
have been identified as spurious signals from DDH47?) so perhaps will try a 
slightly different frequency next time.

So PSK31 obviously works quite well on LF provided signal levels are 
adequate - I got the impression that a signal that was comfortable copy in 
CW would also give good copy in PSK31. It has to be said that QRN was at 
very low levels last night, so it might not be so good during the summer 
months. I think "PSK08" could be worth trying for an extra bit of SNR. 
Also, there is VE2IQ's COHERENT mode, which offers a wide selection of baud 
rates and also error correction - I had a QSO with G4JNT some time ago 
using this mode, and it worked very well. It has the drawback of requiring 
a special A/D interface (such as Andy's simple PIC based device), and a 
computer running DOS (although an old, slow computer works fine). Any of 
these modes would be a good way for a non-CW person to get involved on LF.

I see from the space weather sites that geomagnetic conditions were quite 
disturbed last night, along with the reports of aurora; I'm not sure if 
this has anything to do with the fading we experienced - I have observed 
similar slow, deep fades quite often on the DCF39 signal, and also on 
signals from PA, MM0ALM and sometimes even as close as G3KEV.

If anyone would like to try a sked or tests in PSK31 or other modes, please 
let me know.

Cheers, Jim Moritz
73 de M0BMU