[Lowfer] RE: PSK31 on LF

[James Moritz]

Dear Lowfers,

This mode has been used from time to time over this side of the pond on
LF - I have done some operating using the PSK31 modulator/decoder
functions of DL4YHF's Spectrum Lab software. It works quite well when
there is little QRN, as others have said, with a barely audible signal
producing correct copy. However, each static crash above a certain
threshold corrupts a character, so it becomes unusable when conditions
get noisy, producing mostly gobbledygook. Wolf also produced a "PSK08"
mode for Spec Lab, essentially PSK31 slowed down by a factor of 4. This
did pretty much what you would expect - it was 4 times slower and would
work with about 6dB less signal; it was also somewhat better with QRN,
presumably due to a longer integration time averaging out the QRN
spikes.

The weakness of PSK31 for LF seems to be that there is no error
correction used; each static impulse knocks out one bit, and so there is
a 50% chance that the current character is corrupted. VE2IQ's "Coherent"
PSK mode is better in this respect; with it's forward error correcting
codes, it produces accurate copy with quite high levels of QRN.

Cheers, Jim Moritz
73 de M0BMU