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New soundcard modes via satellite


About 6 years ago, Peter Klein (KD7MW) and I had some fun with digital 
soundcard modes PSK31 and Hellschreiber via satellite. See Peter's article, 
"Exotic Modes In Space" (AMSAT journal, Jan/Feb 2000).

At the time, PSK31 did fair job with AO-10's slow doppler rate, but it was 
immpossible to QSO with PSK31 on LEO's without an aggressive AFC. Feld Hell 
had a tolerance for doppler, but was less sensitive.

I've been experimenting with Olivia and Contestia on FO-29 and VO-52 and 
they seem to be well suited for satellite when configured correctly. I've 
been testing the modes by recording the downlink and then playing it back to 
the soundcard running MixW.

The AFC control in MixW ( www.mixw.net ) seems to track well up to 25hz/s. 
The best bandwidth / tone combination seems to be 500Hz/4 tones with Olivia 
and 500Hz/8 tones with Contestia. The AFC seems to track better with a 
smaller number of tones.

Both modes compare well with PSK31's sensitivity and there's no doubt that 
they will work wonders for low-power stations on DX-Sats. In the meantime, 
both modes seem to do well with LEO's.

If anyone would like the playback recordings, please e-mail direct.

73, Tony KT2Q
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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