# Re: GRC FFT Plot

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 *
Engineering Research and Development for Technology (ERDT) Scholar
University of San Carlos - Technological Campus
Nasipit Talamban, Cebu City, Philippines, 6000
Mobile: +639271525124
Email: [email protected]

“Design is not just what it looks like and feels like. Design is how it
works.” - Steve Jobs

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

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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