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

Ian Buckley ianb at ionconcepts.com
Thu Sep 4 15:53:32 EDT 2014


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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