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RE: [Discuss-gnuradio] PMR data decode

From: Ettus, Matt
Subject: RE: [Discuss-gnuradio] PMR data decode
Date: Mon, 8 Jul 2002 15:04:23 -0700

> Is anyone working on deocding of data found in the PMR bands (e.g. MDT
> terminals, pagers, etc.).

I'm not familiar with those specs, but if you send more info, and possibly
some audio samples (assuming this signal is narrower than 20 kHz BW), it
might be pretty easy to decode. 

> I'm quite impressed with GNU Radio so far
> having got a nice display of the waveforms using the audio scope
> example. I'm not sure how to proceed in decoding in terms of 
> the modules
> to link together. I envision something along these lines:

It depends largely on what type of modulation it uses.  Assuming FSK, the
chain would most likely be

Quadraure Demod
Data Slicing

> This example is for data where the bits are manchester encoded in
> amplitude when viewed on the scope. (I originally believed this to be
> FSK, but now I'm not sure as I've seen some other data 
> signals that seem
> to be a sinewave at two discrete frequencies, which would necessitate
> further FSK decoding first. Anyway, that's a side issue on my lack of
> understanding of FSK modulation.)
> I've got my head around a lot of the architecture having read through
> the entire mailing list archive and the (limited) 
> documentation, but I'm
> not sure how I would go about getting from an audio input to a data
> output. I connected a VrAudioSource to a VrFileSink, but I'm 
> not sure of
> the format of the data in the file

If I understand your question correctly, the data file output is pretty much
raw binary.  It could be bytes, words, floats, complex floats, etc.


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