On the AMSAT Bulletin Board (AMSAT-BB) Bob Bruninga WB4APR writes:
If someone will build a linear PSK-31 transponder, I have a launch opportunity in 9 months.
All it needs to be is a PSK-31 Linear receiver on 28.120 MHz (3 kHz bandwidth) with AGC coupled to a downlink UHF FM transmitter of about 1 Watt. Should fit on a 3.5″ square card. This is the same as Brno University of Technology has built for prior missions of PCSAT2 on the ISS back in 2006 and the two on the shelf awaiting flights.
Flight delivery by May 2014 (9 months from now).
Brno University, may not have the people to make a third one for this new flight opportunity.
Just a thought for someone looking for a project.
PSK-31 Transponder Concept http://www.usna.edu/Users/aero/bruninga/psk31uplink.html