[amsat-bb] Re: Ideal AMSAT FM Transponder

Walter Holmes Walterh at k5wh.net
Sun Sep 30 13:47:01 PDT 2012

Hey Bob,

 This might also be a great project for balloon launches as well, to be able
to test all the ground station setups.

Any idea if these transponders will be made available to others after this
project is completed ?

It appears that the Small Wonder Labs' PSK device is no longer available,
pending a replacement that's in the works.

Take care,


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Robert Bruninga
Sent: Sunday, September 30, 2012 2:50 PM
To: Amsat - BBs
Subject: [amsat-bb] Ideal AMSAT FM Transponder

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

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
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