Hi, After disconnecting LO cables signal on the daughter-board that imports LOs disappears. So GNU Radio correctly configures distribution of LOs. Also the +/- 90 degree changes happen completely deterministically in given ranges of carrier frequencies.
So the question remains open: what is causing the issue described in the first post of this thread? -- Best Regards, Piotr Krysik W dniu 03.04.2019 o 12:15, Fabian Schwartau via USRP-users pisze: > Hi, > > yes, the result for multiple measurements (start ups of the system) at > a single frequency was different by multiples of 90°. > We did not investigated the problem any further, but I am quite sure > that gnuradio was not synchronizing the channels using the LO-sharing, > although it was selected. So do the test I described. If you see that > he is not using the LO-sharing, you know where to look further. > Keep in mind that it is not necessary to use LO-sharing to get a well > defined phase relation between the channels. Depending on your > frequency and bandwidth settings, it is possible to also achive this, > as all LOs are driven from a common 200 MHz reference clock. > > Best regards, > Fabian > > Am 03.04.2019 um 12:05 schrieb Piotr Krysik via USRP-users: >> Hi Fabian, >> >> W dniu 03.04.2019 o 11:05, Fabian Schwartau via USRP-users pisze: >>> Hi Piotr, >>> >>> we once had a very similar issue. But we also saw this on the same >>> frequency when switching between frequencies. Can you try this as >>> well? Just switch forth and back between two frequencies and just plot >>> one of them? >> >> I'm not sure I understand correctly what you mean. You mean that the >> result for a given frequency was not stable in your case across many >> measurements? In our case this situation was repeating, but the >> application doing the recording was restarted for each measurement. >> >>> As far as I remember the issue was because we were not using the >>> LO-Sharing. We were able to get everything running by using a C++ >>> application and not gnuradio (I can see you are using python - which >>> is basically the same). There was a bug in gnuradio/python causing >>> this issue. >>> You can try to remove one of the LO-sharing cables while doing a >>> measurement and see if the phase suddenly starts to do crazy things >>> (the signal should also be lost). If that is not the case, you are not >>> actually using LO-sharing. >>> >> Do you know what this bug was exactly? GNU Radio didn't configure >> LO-Sharing the way it was specified? >> >> -- >> Best Regards, >> Piotr Krysik >> >> _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
