[Lowfer] Re: PSK08

[James Moritz]

Dear Lowfers,

I used the PSK08 mode included with DL4YHF's Spectrum Lab software a year 
or so ago with quite good results in QSOs with DL4YHF and DF6NM. The 
software worked fine, except for the receive AFC function, which would not 
"settle" to a stable frequency, presumably because it was designed for a 
higher data rate. I'm not sure if Wolf got round to fixing this problem, 
but in practice all I did was to switch off the AFC finction and set the 
fine tuning manually - it wasn't needed anyway, as all the stations could 
set their frequency accurately enough that it would work straight away 
without adjustment, not hard to achieve at LF. The standard output is phase 
keyed audio from the soundcard at a user-selected frequency. For my 
station, I needed a logic level signal for the amplitude- and phase 
modulators of my TX, and Wolf was kind enough to produce a modification 
that generated an on-off keyed audio tone instead of PSK, which I set to 
about 5kHz, then rectified and used as the logic level drive for the TX 
modulators. I suggest you contact Wolf direct for info.

On the air, It did more or less what you would expect - it was like PSK31 
only  4x slower, and would work with about 6dB weaker signals - as a rough 
idea, PSK31 worked with what would have been very weak but readable CW, 
while PSK08 gave good copy with signals that were barely detectable by ear. 
The weakness of both modes was that QRN crashes would corrupt characters - 
PSK31 was purposely designed with no error correction, so a spike of noise 
big enough to corrupt a single bit will produce an incorrect character. 
This meant it wasn't great under noisy conditions on LF. PSK08 was somewhat 
better, presumably because a longer integration time meant a bigger QRN 
crash was needed to mess things up.

Cheers, Jim Moritz
73 de M0BMU