[amsat-bb] Two way SSTV exchanges using PSAT2

[Robert Bruninga]

The PSAT2 team has decided to enable the 10 meter uplink for user SSTV
experimentation with two-way user SSTV communication.

PSK31 usage has been light and SSTV downlink seems almost perfect as
reflected in PY5LF's example posted before, so why not let people do 2-way
SSTV?  Simply transmit SSTV using SSB on the 29.4815 uplink WHILE someone
else is transmitting PSK31.

Ah, there's the rub.  The transponder has to see a PSK31 modulation
somewhere in the passband (not used by SSTV) in order to key up the
transponder.  AND the uplink station has to do the Doppler correction.  But
unlike PSK31, SSTV is not phase coherent and so RIG control using any
satellite software can do fine.  Also, if you can run two instances of
SSTV, you could see your own downlink on 435.350 for Quality control!

Maybe we can enlist the authors of SSTV software to not only generate the
SSTV tones, but also a mild PSK31 tone carrier down below 400 Hz.  Anyone?

Actually, the "psk31" tone only needs to have 31.25 Hz AM modulation on the
tone carrier to do the trick, doesn’t really have to be PSK31..

Bob, WB4APR