[amsat-bb] Ideal AMSAT FM Transponder

Robert Bruninga bruninga at usna.edu
Sun Sep 30 12:49:53 PDT 2012

The ideal AMSAT FM transponder for a cubesat is the PSK-31 transponder
being developed for the Naval Academy PSAT mission.

With an FM downlink, anyone can receive it with an HT and a laptop with
PSK-31 software.  And anyone with a 10m PSK-31 uplink can transmit to it.

The reason it is ideal is that it is a multi-user transponder supporting
up to 30 users at the same time.  Everyone can transmit horizon-to-horizon
and see everyone else.  A big QSO party in the sky:


And since it is FM, Everyone tuned into the downlink SEES THE SAME
WATERFALL and sees EXACTLY where they are in the downlink.  A small uplink
doppler adjustment can keep each station locked to his chosen channel in
the passband.

Everyone can talk to everyone if they want, or go one-on-one too.

The SSB uplink and UHF downlink transponder fits on a smaller than 3"x3"
circuit board being developed by Mirek Kasal at Brno University.

If we could just get more Cubeats to fly these things, we would have all
the joys of multi-user transponders, and yet they fit well in any cubesat.
The ONLY problem is the HF wire antenna.  Ours is going to be a 4 or 6'
whip of Nitinol Wire.

In addition to thes PSK-31 transponder, PSAT also supports the usual APRS
AX.25 transponder on 145.825 too.  Launch is planned for Summer 2013.

Bob, WB4aPR

More information about the AMSAT-BB mailing list