I have already been talking with @dl7ndr via email about this issue I am having but figured I would move it to a forum post to see if others have any insight about my issue (plus hopefully document my findings for others who try to do the custom transmit route).
I have been trying to digipeat to Lasarsat, Crocube, and GRBBeta (although primary Lasarsat) using inexpensive hardware with effectively no promising results. Previously I was using the following setup:
This setup yielded typically ~50Ws at the antenna input however I couldn’t get the PTT transfer between RX and TX quick enough. Therefore I swapped to using a different FSK transmitter (well technically lora transmitter but running in FSK mode) and produced the following setup.
This new setup seems to work far better (and still provides ~50Ws into the antenna input) than the previous transmit based SDR setup especially now that I added an external clock input into the SX1278. However, I still can’t seem to get any luck with getting decent digipeats.
@dl7ndr suggested that my modulation amplitude/gain on the SX1278 seems to be potentially too low but I don’t think there is anyway to improve that. For reference, I have attached a fm recording of the output of the PA (attenuated heavily down to around -75dBm into the PlutoSDR RX). Any suggestions would be appreciate for what I can try next.
test_transmit.wav.zip (1.6 MB)