Hello! I'm trying to build QPSK based system on GNURadio. I'm using two USRP B205-mini boards as transmitter and receiver, also I got B210 board that I run gqrx on to watch what is really going on. I noticed a strange behaviour on my tests, so I began to investigate it and ended to a very simple graph, that is in attachment. On a frequencies that are multiple of 10Mhz, like 1020Mhz all works like expected and sonogram looks good. If I tune to any other frequency, even 1Hz more or less, the sonogram is full of pulsations and frequency of that pulsation is depends of exact tune frequency. I attached some screenshots of that pulsations. On receiving part that pulsations cause many errors while decoding. I got another board, LimeSDR-Mini, and no such behaviour observed while running graph on it. I wonder what is going on, and how can I fix this problem. Thank you.

Just to be clear, you see these pulsations when transmitting with a b205mini, but *not* with the b210? Is the b205mini a bare board or an industrial model with a case and aluminum heat sync? Sam Reiter Ettus Research On Wed, Dec 11, 2019 at 11:48 PM Геннадий Казачёк via USRP-users < usrp-users@lists.ettus.com> wrote: > Hello! > I'm trying to build QPSK based system on GNURadio. > I'm using two USRP B205-mini boards as transmitter and receiver, also I > got B210 board that I run gqrx on to watch what is really going on. > I noticed a strange behaviour on my tests, so I began to investigate it > and ended to a very simple graph, that is in attachment. On a frequencies > that are multiple of 10Mhz, like 1020Mhz all works like expected and > sonogram looks good. If I tune to any other frequency, even 1Hz more or > less, the sonogram is full of pulsations and frequency of that pulsation is > depends of exact tune frequency. I attached some screenshots of that > pulsations. > On receiving part that pulsations cause many errors while decoding. > I got another board, LimeSDR-Mini, and no such behaviour observed while > running graph on it. > I wonder what is going on, and how can I fix this problem. > Thank you. > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >