Re: [Discuss-gnuradio] AM demodulation

[Martin Dvh]

Thanks for all the tips.
I didn't realize that the absolute value function was already there in 
gr.complex_to_mag ()

Seems that I was trying the right way.
Data->IQ demodulator->gr_complex_to_mag(==abs(complex value)->low pass...

I did find the example from Chuck Swiger very usefull.

David Carr wrote:
>On a cursory glance though, this stikes me.
>What is your signal source? If its the AM broadcast band the filters 
>below might be a bit too wide.
>As a reference the entire (mid) AM broadcast band is about 1.1MHz wide 
>and the stations themselves
>are only 10KHz wide.

I know, but narrow filters son't seem to work with my setup.
Anything narrower then a few hundred kHz gives no audio or only a short 
1 second burst of audio and then dead silence.
Strangely enough, I found out useing the code of Chuck that adding a 
dummy block (adj_in = gr.add_const_ss(0)) makes filters as narrow as 2.5 
kHz work in my setup.
I am sending a seperate message to the list about this, I have no clue 
what is happening here.

I want to use the am demodulation to receive commercial air traffic 
communication ( around 120 MHz, AM modulated, 10 kHz wide channels)
But for testing I use a signal generator and AM broadcast signals.
Better a too wide filter and sound then nothing at all.


Greetings,
Martin