Much easier to use an HP signal generator and drive it via the GPIB port. Less noise, more accurate, etc..
A nit to program across GPIB. Slightly more complex than talking to a TNC.
Norm n3ykf
On Mon, Apr 17, 2017 at 10:37 AM, Robert Bruninga bruninga@usna.edu wrote:
Some students built an HF inverting SSB transponder simulator. (4 diodes, and a siggen at 58 MHz) so they can then use two FT-817’s on the 21.4 MHz uplink and 29.4 MHz downlink) for our next satellite: http://aprs.org/hfsat.html )
Now we want to use an USRP 2922 SDR as the programmabel oscillator around 58 MHz so we can simulate Doppler.
Can anyone whip out some code to make the oscillator follow a Doppler Ramp in freuqncy from say 58.100 to 58.900 MHz over a ten minute pass. That should be easy enough for one-observer. Can just be linear for now (simulating a low pass).
But then once that is done, we need the driver to then FLIP the Doppler shift instantly in the opposite direction to simulate the shift seen by another observer at the other end of the pass. This is another layer of complexity, but we will simply have a push button input to shift between the two states when one station or the other is transmitting.
But for now, the students just need some handholding to get the basic SDR acting as a signal gen at 58 MHz and how to input the freqncy ramp to it.
Thanks
Bob, WB4APR _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb