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

Ian Buckley ianb at ionconcepts.com
Thu Sep 4 16:12:31 EDT 2014


Good point, I answered that very quickly without looking at the downloads. Do you understand Marcus's point about direct conversion architectures? It was perhaps more appropriate.



On Sep 4, 2014, at 1:04 PM, Harold Daniel Moreno Urbina <haroldmk at gmail.com> wrote:

> 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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