Re: [Discuss-gnuradio] GRC FFT Plot

[madengr]

Same procedure I outlined before.  You need  to feed a CW tone (via cable)
directly into the USRP and spectrum analyzer, compare spectrum amplitudes,
and multiply the USRP samples by 10**(offset_dB/20.0).  Noise or a modulated
signal makes things more difficult since spectrum analyzer must be put in
noise marker mode.  Just use a CW tone.
Lou
  


Jan wrote
> Actually, you were right at first madengr. My transmitter is USRP1 with
> WBX
> 50-2200 while my receiver is USRP N200 with TVRX2 and spectrum analyzer.
> Can you give me suggestions on how I can match the amplitude on both the
> spectrum analyzer and the USRP's? Attached is a screenshot of my
> experiment
> on our lab.
> 
> Using just the GRC Signal Source and Noise Source, I was able to display
> the desired power amplitude in dBW with less than 10 dB loss by varying
> the
> amplitude of each block. For the Signal Source block, the amplitude was
> 6.31 exp -8 (-144 dBW). For the Noise Source block, the amplitude was 2
> exp
> -8 (-154 dBW). GRC FFT produces -137 dB and -159 dB respectively.
> Therefore
> I can say that these dB values in the FFT plot are in dBW.
> 
> Best,
> 
> *Gerome Jan M. Llames *





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