Re: [Discuss-gnuradio] Demodulating a MPT1327 signal

[madengr]

Post your GRC file.  I tried it just as you implemented and it is working
here.  I would have choose different sample rates and topology, but
nonetheless it works.  Gain of 100 (dB) should not be a valid UHD value as
it tops out at 81 for the B200, and 31 for the WBX.  It still works though.

Can you trace the signal down the flow with the GUI instrumentation? 


Weaver, Tyler [GCS] wrote
> MPT1327 uses MSK on its control channel.  I am attempting to use NBFM
> Receive to demodulate the signal into a WAV file that I can play back and
> use sdrtrunk to decode it.  So far my best attempt is set up as follows:
> 
> USRP
> Sample Rate: 250k
> Center Freq: 652.625M
> Gain: 100
> 
> Frequency Xlating FIR Filter
> Decimation: 1
> Taps: firdes.low_pass(100,samp_rate,10e3,1e3)
> Center Frequency: 0
> Sample Rate: 250k
> 
> Rational Resampler
> Decimation: 250k
> Interpolation: 192k
> 
> NBFM Receive
> Audio Rate: 192k
> Quadrature Rate 192k
> 
> Wav File Sink
> Sample Rate: 192k
> Bits per Sample: 16
> 
> The output of this seems to be just noise and is not working.
> 
> Thank you.
> 
> --tyler
> 
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