I tested again and was able to simplify things in SoapySDR. Instead of specifying the frequency for “RF” and “BB” (so I guess the LO and NCO internally), I can simply specify the frequency for both channels like so:
setFrequency(RX, 0, 2429e6, NULL);
setFrequency(RX, 1, 2471e6, NULL);
I end up with similar results as with my previous test:
setFrequency(RX, 0, "RF", 2450e6, null);
setFrequency(RX, 1, "RF", 2450e6, null);
setFrequency(RX, 0, "BB", -21e6, null);
setFrequency(RX, 1, "BB", +21e6, null);
so I guess the underlying code takes care of setting things properly so that both channels can listen at different frequencies, as long as they are not too far apart.
I’m not sure why but I’m not seeing the wavy spectrum even with 60MHz bandwidth per channel.
I still see some weird spike at 2420, 2450 and 2480MHz though, that disappear after a 3 to 5 milliseconds:
- 3 big visible spikes
- that disappear after ~5ms
- 3 big visible spikes, plus a real signal at 2445MHz
- only the real signal is visible after ~5ms
In mono channel I’m not seeing those weird spikes. Is this normal?