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

Harold Daniel Moreno Urbina haroldmk at gmail.com
Thu Sep 4 15:24:23 EDT 2014


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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