[amsat-bb] Two way SSTV exchanges using PSAT2 (update)

[Robert Bruninga]

PSAT2 has plenty of power all the time to support the PSK31 and SSTV HF/UHF
transponder because it lost its VHF xcvr.  So this mode will be around a
long time with plenty of power.  Same goes for PSAT since most of the time
its VHF xponder is off.

And I looked up the PSAT PSK31 telemetry is at 312 Hz and the PSAT2
telemetry is a 374 Hz, so any pilot tone between about 400 and 800 Hz
should be fine and not interfere with the SSTV.

On Sat, May 16, 2020 at 12:13 PM Robert Bruninga <bruninga at usna.edu> wrote:

> I dont think a baseband 31.25 Hz tone will work.  There has to be a tone,
> say 400 Hz that is then AM modulated at 31.25 Hz.  The 500 Hz or so lets it
> get through your transmitter audio circuits, and then the 31.25 Hz AM
> modulation of that tone is what looks like PSK31 carrier.
>
> Both PSAT and PSAT2 both have an audio PSK31 telemetry down around 300 Hz
> (I need to look them up) so we need to avoid those areas so as not to
> interfere with telemetry.  And not go above say 800 to avoid being in the
> area where the SSTV tones are.
>
> Bob
> WB4APR
>
> On Fri, May 15, 2020 at 4:27 PM Pedro Converso <pconver at gmail.com> wrote:
>
>> Nice Idea, worth to be tried, as alternative:
>>
>> Use online generator setted to 31.25 Hz that can be adjusting volume
>> using:
>>
>> http://onlinetonegenerator.com/
>>
>> 73, lu7abf, Pedro
>>
>> On 5/15/20, Robert Bruninga via AMSAT-BB <amsat-bb at amsat.org> wrote:
>> > As soon as we see a report that 2-way SSTV through PSAT2 actually works,
>> > then we can solicit the popular SSTV Authors to add the 31.25 Hz
>> optional
>> > modulation that will automatically bring up the SSTV (PSK31 actually)
>> > transponder.
>> >
>> > Will this be the first practical SSTV transponder?  I know SSTV 2-way
>> has
>> > been done before, but with the Very low Doppler shift on the 10m uplink
>> > and the no-tone Doppler on the FM downlink, this should be pretty
>> straight
>> > forward...  And it does not compete with the high demand that prohibits
>> > SSTV via other popular satellites.
>> >
>> > Who will be first? (I updated these comments on the
>> > http://aprs.org/psat2.html page).
>> >
>> > And remember, you can do this on the identical HF/UHF PSK31 transponder
>> on
>> > PSAT too.  That's two satellites supporting this mode.
>> >
>> > And if still people don't use PSAT and PSAT2, for PSK31 or SSTV, then I
>> > guess we could even open up the 10m uplink on PSAT2 to voice contacts!
>> > (Cannot do this on PSAT since its uplink (28.120) is not in a voice
>> > segment.
>> >
>> > Bob, WB4APR
>> >
>> > -----Original Message-----
>> > From: Brian Wilkins KO4AQF via AMSAT-BB
>> > Subject: Re: [amsat-bb] Two way SSTV exchanges using PSAT2
>> >
>> > Concur, I use CQ SSTV on iPhone. Works great! I have also used MMSTV on
>> > Windows laptop. Worst case, record it, clean up audio in Audacity and
>> play
>> > it back with one of those apps listening.
>> >
>> > On Fri, Andrew Glasbrenner via AMSAT-wrote:
>> >
>> >> Until I figured out a problem I was having, I used SSTV by Black Cat
>> >> Systems on my Iphone in the shack. I just put the phone in a headphone
>> >> cup on the desk and away we went.
>> >>
>> >> 73, Drew KO4MA
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>> > expressed
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>>
>