Hello, thanks for your attention. > I always thought these pulsations were due to some kind of bug with > Gqrx. If you change the FFT size, the rate of pulsation changes. No, it doesn't. I've tested, FFT size doesn't affect rate of pulsation.
> Also, you don't see this on a real spectrum analyzer, even an inexpensive one. I don't have one, but as I said before, decoding is failing when this pulsations are on the air. So, I believe, that gqrx is fine here. > the stripes go away when you turn of the USRPs? Yes, when I stop graph, this pulsations are gone > Also, the stripes aren't there, either, when you use the Lime on the > same 1.011 GHz frequency, exactly? Yes, it is correct, I just disable USRP block, enable Lime block and swap devices. > My suspicion is that this is mostly USB3 emissions I've tried to connect through USB2, result is the same > Also, are you using an external power supply for your USRPs No, they are connected to my host pc by USB only. On Sat, 21 Dec 2019 at 21:15, Ron Economos via USRP-users < usrp-users@lists.ettus.com> wrote: > I always thought these pulsations were due to some kind of bug with > Gqrx. If you change the FFT size, the rate of pulsation changes. Also, > you don't see this on a real spectrum analyzer, even an inexpensive one. > > Ron > > On 12/21/19 09:25, Marcus Müller via USRP-users wrote: > > Just to rule out interferers: > > > > * the stripes go away when you turn of the USRPs? > > * Also, the stripes aren't there, either, when you use the Lime on the > > same 1.011 GHz frequency, exactly? > > > > My suspicion is that this is mostly USB3 emissions (those could be, but > > not necessarily are, happening through the USRP itself, or through > > cables, or through your host computer. > > > > If your sampling rates allow it (they do, I think you're using 500 kHz > > only¹), try to use a USB2-only cable or port and see whether these > > disappear. > > > > Also, are you using an external power supply for your USRPs? If this is > > actually an interferer, it might as well be some periodic behaviour of > > the power supply. > > > > Best regards, > > Marcus > > > > > > ¹That's a sampling rate that should work on B200 and B20xmini, but it's > > uncomfortably low – try with 1 MHz and host-side resampling, maybe? > > > > On Wed, 2019-12-18 at 21:28 +0300, Геннадий Казачёк via USRP-users > > wrote: > >> Hello, Sam! > >> No, I use two devices as transmitter and receiver and third board I > >> use just to observe sonogram. > >> Pulsations exist on both b205 and b210 devices if I use them as a > >> transmitter and not exist if I use as transmitter another vendor's > >> device - LimeSDR. > >> > >> All 3 USRP devices are industrial with metal case, and LimeSDR is > >> not. > >> > >> On Wed, 18 Dec 2019 at 21:26, Геннадий Казачёк < > >> gena.kazac...@gmail.com> wrote: > >>> All 3 USRP devices are industrial with metal case, and LimeSDR is > >>> not. > >>> > >>> On Wed, 18 Dec 2019 at 21:25, Геннадий Казачёк < > >>> gena.kazac...@gmail.com> wrote: > >>>> Hello, Sam! > >>>> No, I use two devices as transmitter and receiver and third board > >>>> I use just to observe sonogram. > >>>> Pulsations exist on both b205 and b210 devices if I use them as a > >>>> transmitter and not exist if I use as transmitter another > >>>> vendor's device - LimeSDR. > >>>> > >>>> On Wed, 18 Dec 2019 at 18:49, Sam Reiter <sam.rei...@ettus.com> > >>>> wrote: > >>>>> 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 > >>>> > >>>> -- > >>>> Геннадий Казачёк > >>> > >>> -- > >>> Геннадий Казачёк > >> > >> _______________________________________________ > >> USRP-users mailing list > >> USRP-users@lists.ettus.com > >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > _______________________________________________ > > USRP-users mailing list > > USRP-users@lists.ettus.com > > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > -- Геннадий Казачёк
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