On a USRP2 thats a harmonic of the on-board 100MHz clock. One excellent way to deduce when you are dealing with a spur thats LO related is to use offset tuning to move the LO relative to the center of your band of interest. See: https://files.ettus.com/manual/structuhd_1_1tune__request__t.html <https://files.ettus.com/manual/structuhd_1_1tune__request__t.html>
> On Jun 25, 2018, at 3:15 PM, Farhad Mirkazemi via USRP-users > <usrp-users@lists.ettus.com> wrote: > > Hi all, > > I attached the two spectrum snapshots with no antenna connected (which means > what I'm seeing is just pure noise?)to usrp2 setting the center frequency at > 1590 MHz, one using sc16, fs 25 MHz and the other sc8 wireformat fs 50 MHz; > regardless of the spike at 1600 MHz (10 MHz off the fc) which I don't know > why it shows up on both spectrum (I can interpret the spike at the center > frequency as dc component but don't know about this one); so it looks like > for the sc8 the spectrum has been folded around center frequency where for > sc16 wireformat it looks normal. can you please explain why is that and how > to fix this? > > Thanks, > > > > > On Friday, June 22, 2018, 5:52:23 PM EDT, Marcus D. Leech via USRP-users > <usrp-users@lists.ettus.com> wrote: > > > On 06/22/2018 05:43 PM, Farhad Mirkazemi via USRP-users wrote: >> >> Hello all, >> >> I'm recording RF signal at 1.5 GHz using usrp2 with wbx daughterboard of >> fixed BW of 40 MHz; since I'm interested to capture the whole BW, I set the >> over-the-wire format to sc8 to be able to have 50 MSps rate; as example >> rx_samples_to_file suggests, there is no "byte" or "char" format to store 8 >> bit IQ samples; now, if I use "short" type and try to read my binary file >> using matlab, for example, and use the same "int16" format as I was doing >> for SC16 wireformat, i.e interpreting it as I1, Q1, I2, Q2 ..... using >> "int16" reading format, the spectrum looks not the way it should. I know it >> also has to do with the host cpu format which in my case it is 64 bit >> processor but I don't know how to manage the transformation between the host >> and the packet router. Can some please explain how it works and if possible >> how to interpret the data on platform other than uhd? it is also appreciated >> if explain how I could store using 8 bit format so that the file size be >> reduced to half. >> >> Thanks, >> >> > You may need to tweak the dynamic range in the device arguments, using > "peak=0.01" or even "peak=0.001", depending on hows strong your > signal is. > > Also, could you describe what you mean by "not what it should be" ?? That's > a little vague. > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > <Screenshot from 2018-06-25 17-58-12.png><Screenshot from 2018-06-25 > 18-00-34.png>_______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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