[Discuss-gnuradio] How to simulate a Zoom in FFT display ?

[William Pretty Security]

Hello all;

 

I have a 40KHz carrier that I want to be able to check for modulation.

The ‘source’ is the audio source in GnuRadio Companion.

 

I have tried a number of things and nothing seems to work for me.

I have the source, followed by a 40KHz Bandpass filter and a frequency translating FIR filter block.

The output of the BPF and FIR filters go to separate FFT GUI’s so that I can see what is going on.

 

What I am trying to implement is the equivalent of the “Span” and “Center Frequency” functions on a spectrum analyzer.

The Center Frequency is easy, using the Translating FIR block, but I can’t figure out how to do the Span/Zoom function.

 

I Google searched and found a couple of SDR’s with this function, but it appears to be “hard coded”.

 

Does anybody know how to this in GnuRadio Companion ??

 

Thanks …

 

Bill