It's not behaving how I expect, indicating I'm missing some knowledge. Direct sampling quickly picks up the 3V source if and only if there is no resistor between it and the antenna port, even if the resistor is very small, giving the same voltage on a voltmeter.

Given this isn't the primary goal atm and takes some learning, I might think about it a bit, maybe try harder to flash my oscilloscope firmware.

Or I could switch over to oscilloscope stuff.

I found a bug in pysoapysdr I could contribute, maybe.