Re: [Discuss-gnuradio] Spectrum Analysis with FFT plotting

[Sebastiaan Heunis]

Ujala

With a decimation of 250, your USRP will only provide you with the
samples from -128kHz to 128kHz-1.  So, unless your station of interest
is very close to DC, you won't see it on an FFT of your data.  If your
signal is at an IF of 5.75MHz, you will need to sample at 16Msps in
order to digitise it.

Try an experiment.  Tune your USRP to 106.2MHz (so that your radio
station now sits at DC).  Set the decimation to 250
(Fs=64e6/250=256ksps).  Now capture 1s of data and do a 256000 point
FFT in Matlab.  You should now see a nice FM signal at DC.

You can use the usrp_wfm_rcv.py gnuradio-examples script to see what
happens in the FM band where you are.

Sebastiaan