I have been researching the idea of building a CubeSat Simulator we can use in a "classroom" environment, which simulates four modes of amateur satellites:      *  U/v FM repeater, with doppler effect      *  VHF APRS digipeater      *  VHF SSTV transmitter      *  V/u linear transponder, with doppler effect

I think this would be a great tool to use in presentations/demonstration, as well as to allow operators, using their own equipment, to take a "test drive" on all of the amateur radio satellite types currently in orbit. My initial plan is to use a Raspberry Pi and a LimeSDR Mini software defined transceiver, all stuffed inside a 3d printed, 1U Fox satellite.  [Alternatively, I could use the RPi as the transmitter and an SDR-RTL dongle as the receiver.] On the software side, I am looking at running GNUradio and Direwolf.  The trickiest part will be simulating doppler effect on the UHF receiver (uplink) side for FM and linears. This is all new to me and my only related education comes from what I have been able to find on the internet.  If you have any recommendations and/or experience with GNUradio, I could really use the help. 73, Robert Bankston, KE4AL