Tests with PSK31, PSK10 and more..]

[Andre' Kesteloot]

DL4YHF@aol.com wrote:

> Hello group,
>
> Just did a few tests (off-air) using a slow variant of PSK31 which could be
> called  PSK10, PSK05 etc.
> Instead of the signaling rate of 31.25 symbols/second from G3PLX's original
> PSK31, I used only 10 or 5 symbol/second. This reduces the bandwith to 1/3rd
> or 1/6th of the original PSK31 signal, and thanks to the nice coding scheme
> used in PSK31, the character transmission speed is still acceptable for a
> 'real' QSO.
> ( For those who are not familiar with PSK31:
>    It uses a code set called 'Varicode',
>    which uses fewer bits for frequent letters like 'e'
>    than the others, similar to the Morse code.)
>
> To test the effect of the reduced symbol rates, I added white noise to the
> signal and compared the decoded text with the original PSK31. I decreased the
> signal/noise ratio until the decoded text became undetectable.
> The results were as expected: Using "PSK10" instead of "PSK31", the noise
> could be increased about 3 times in amplitude for the same detection quality.
>
> However, if you want to test the 'slow PSK31 variants' on air. Because all
> PSK31 programs I had did not support other symbol rates than 31.25sym/sec, I
> modfied the PSK modulator and detector from WinPSK (by AE4JY) and stuffed
> them into Spectrum Lab.
> I just uploaded a new release of SpecLab (V1.63) with a built-in 'digimode
> terminal'. It is available at www.qsl.net/dl4yhf/spectra1.html. Beta testers
> are welcome.  Bug reports please to DL4YHF@qsl.net. How about some 'QRPP'
> tests,  Geri ?
>
> ------------ snip ------------
> Drifting frequency of DF0WD's CW signal:
> The problem is a result of the poor stability of the main oscillator in my
> old Icom IC706. The fan blows warm air from the final amp towards the 'master
> crystal'. I watched the Loran lines yesterday, and found them 'wandering'
> around the sreen for about 30 seconds after one over (using only normal CW
> here).
> I thought about buying a 'TCXO' for the IC706, but the cost of about 120euro
> for that tiny piece of PCB kept me off. Any better ideas ?
> ----------- snip -----------
>
> 73's Wolf  (DL4YHF, qrv on LF only from DF0WD).