I wanted to test all TX and RX ports on my board in GNU Radio Companion and run into strange problem with using second TX channel. I want to transmit the same signal at different frequencies (shift by, say, 15 MHz or so) via TX1_1 and TX2_1 ports. As I read it here, I am supposed to set “Num Channels” to “2”. Also I have figured it out than you also need to add “nchan=2” to device arguments (it took me a while to find that information). Then I was actually able to run the flowgraph, but the problem is that it looks like both TX1_1 and TX2_1 ports are transmitting only signal prepared for TX2_1 at its frequency (moreover, shape of this signal transmitted via TX2_1 is kind of periodically attenuated in frequency domain).
I have also tried ‘UHD USRP Sink’ block (I have set “Num Channels” to “2” and “Stream chanels” to “[0,1]”), and again was able to run the flowgraph but it did not transmit anything at all.
Finally I have tried PothosGUI with all combinations of “Channels” and “Frontend Map” settings I could have think about, but with no luck.
So, has anyone succeeded with actually transmitting anything via TX2_1 port in those environments? Or, even better, transmit and receive by both channels at the same time (say: transmitting 10 MHz wide signal by TX1_1, receive it via RX1_L and, at the same time, transmitting the same 10 MHz wide signal by TX2_1 at frequency shifted by 15 MHz and receive it via RX2_L)?