Re: [Discuss-gnuradio] Getting the max amplitude of an FFT plot (FFT sink)

[Dan Rosenqvist]

Anthony Hsu wrote:
> 
> Hi,
> 
> I am trying to write a simple program that changes the TX frequency in
> response to some RX stimulus.  I want the TX frequency to change if any
> part
> of the RX signal in a band I am monitoring exceeds a threshold amplitude.
> 
> My problem is I don't know how to get the amplitude of the RX signal in
> the
> FFT plot.  The "peak hold" option saves the max amplitude at every
> frequency
> across the band you are monitoring, so if you could access the amplitude
> values of these saved peaks, you could find the max amplitude and test if
> it
> exceeds the threshold amplitude.  But I don't know where (what variables
> or
> what function) the peaks are saved.  Could somebody point me in the right
> direction?
> 
> Best regards,
> Anthony
> 
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> 
> 

Hi Anthony,

I'm working on a similar project, and with some minor alterations to
usrp_spectrum_sense.py you should be able to get peaks from the fft sink.
For more info on the coding, please see Firas excellent explanation:
http://www.nabble.com/Some-usrp_spectrum_sense.py-code-Explanation-td21209623.html#a21209623

Regards,
Dan

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