I am using Zynq706 with an FMCOMMS3 board and playing with various GNURadio blocks to get basic signals in and out. For some reason my tx output power is extremely weak and barely reaches -50 dBm. I have tried to set some tx gain on it but I get the "Unable to set attenuation" iio error for any positive gain. The receive chain works fine though with and without gains. Any idea what might be the reason?