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RE: PC Soundcard - a good P3D 400 Bd TLM receive modem



> David Brown <djbrown@bigpond.net.au> wrote:
> 
> >Has anyone tried do this via a PC soundcard? It seems
> >possible to me, or am I missing something.

Yes Dave, it IS possible, and AMSAT-France is currently working on the
subject.
In 1998, Ghislain F1HDD developped such a programme for the defunct RS 19 /
Sputnik 42 project.
This software, called PSKDEC, uses the PC soundcard to decode 400Bd PSK
data, to display them on the screen and to store them into bin files for
further processing.
PSKDEC is today a DOS software which includes a Costas loop, clock
regeneration, block and character synchronisation, and data storage.
Two weeks ago, I performed the first "space" tests, by using a real bird.
To be sure to test the programme in heavy conditions, I deliberately choosed
to use FO-20 during a crowded week end period.
Many sets of test frames were sent to the mode J satellite during several
daylight passes and the downlink was recorded and then processed by PSKDEC.
The results were successful, in spite of:
- the heavy QSB produced by the satellite AGC (many stations were using the
linear transponder that week end),
- some QRM generated by adjacent contacts,
- the steep frequency jumps occuring each second, which were produced by the
Station programme used as Doppler shift corrector.
My FO-20 PSK audio wav files are available to those wanting to test their
P3-D hardware or software modems with "real life" signals.

PSKDEC, as a DOS version, was used to validate the algorithms.
Christophe Mercier and Ghislain F1HDD are now working on a Windows version
which Man Machine Interface is expected to be more attractive :+))

Cheers

Jean-Louis F6AGR
 
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