[USRP-users] Not getting white noise in a USRP N210

Harold Daniel Moreno Urbina haroldmk at gmail.com
Thu Sep 4 16:04:33 EDT 2014


But neither 2.45 GHz nor 2.42 GHz are factor of 100 MHz. The other
frequencies used are (1.8 GHz, 900 and 300 MHz).


2014-09-04 13:53 GMT-06:00 Ian Buckley <ianb at ionconcepts.com>:

> Very likely it's a harmonic of the 100MHz clock used extensively in the
> N210.
> Try tuning to a frequency thats not a factor of 100MHz and see if it is
> still there.
>
> On Sep 4, 2014, at 12:24 PM, Harold Daniel Moreno Urbina via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
> Hello,
>
> When using USRP N210 without an antenna I would expect to receive white
> noise, right?. But consistently I am getting signal at center frequency
> well over 20 dB compared to other frequencies and 30 or dB over the signals
> near the edge.
>
> Anyone knows what is happening here? Is something wrong in the USRP or in
> GNU Radio? or me? Thanks.
>
>
> I am using USRP N210, GNU Radio 3.7.2.1 (version of last friday) over
> Ubuntu 14.04.
>
> I uploaded some screenshots of the FFT of the received signal, always
> 10Msps and getting about 5 minutes of signals. I used the example included
> in GNU Radio uhd_fft.grc and a custom flowgraph icluding only a USRP source
> and a FFT sink.
>
> ----------------------------------------------------
> uhd_fft.grc
> ----------------------------------------------------
>
> center frequency 2.45 GHz:
> https://mega.co.nz/#!WFE3UTRZ!AO04usGbl9TBa5-mCUPz7FYW2IabY5nbo5zZqSWwaM4
>
> center frequency 2.42 GHz:
> https://mega.co.nz/#!Hc0UzBJA!fSfgScdXPJ_phKdIWUKcNseonlKQt3m64yvYMR0bDhs
>
> ----------------------------------------------------
> Custom USPR2FFT
> ----------------------------------------------------
>
> center frequency 2.45 GHz:
> https://mega.co.nz/#!Hd9RyApS!FzsY5yxr5e6dJaAAO7Ww2O4BFefyCk6MDPN6ffcOs_g
>
> center frequency 1.80 GHz:
> https://mega.co.nz/#!LQcTkDjb!NQ7rIe1PDgRFCp547_U3mhxxxzsvQilPV-esTo7nHa4
>
> center frequency 900 MHz:
> https://mega.co.nz/#!eZ1TFbSY!nkt-n1mlC54aFfDwvqoJIJd7-a7gMB2GBLLhyclxxcs
>
> center frequency 300 MHz (out of SBX used operational band):
> https://mega.co.nz/#!mJ8EESwR!lI_0r4RvvTncxwwMnpEVAvrwsVhcHzLX7H6C7TA4Cj0
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>
>
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