[USRP-users] spectral leakage ?!

James Humphries james.humphries at ettus.com
Fri Oct 2 09:55:13 EDT 2015

Some LO leakage is typical with the system. When you say sometimes not
necessarily at the center frequency, how far away from center is it?


On Thu, Oct 1, 2015 at 7:53 AM, Amina M. Fellan via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hello everybody !
> I'm using 2 USRPs N210 equipped with SBX daughterboards with GNU Radio to
> establish BPSK communication over ISM band. For the latter, I started with
> the benchmark_tx/_rx.py examples.
> currently I'm trying to measure the SNR at the receiver. I tried using the
> SNR estimation blocks in the GRC but they seem to be giving erroneous
> readings, so I decided to try with a spectrum analyzer to estimate the SNR
> using (S+N)/N.
> I noticed that even when there's no transmission going on, so trying to
> measure the noise floor, a signal appears on the spectrum and sometimes
> even not necessarily at the center frequency. This also can be seen using
> the uhd_fft script from GNU Radio. Attached is a photo of how the spectrum
> looks if the USRP is on without transmitting/receiving !!
> Any clues what is causing this problem ??
> Thanks for your time !
> Cheers,
> Amina
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