Just speculating, but I wonder if what you're seeing is a result of quantization error...
On Mon, Jun 25, 2018 at 11:55 PM Farhad via USRP-users < usrp-users@lists.ettus.com> wrote: > Thanks Ian for your answer; but my main question still remains unanswered > which is why with different wire format sc8 and sc16 the spectrum is > different? How may I interpret this? > > Thanks, > > On Jun 25, 2018, at 9:44 PM, Ian Buckley <i...@ionconcepts.com> wrote: > > 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 > > > 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 > 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 > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > -- Very Respectfully, Dan CaJacob
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