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
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