[Discuss-gnuradio] C source for AM modulation/demodulation

[Benjamin J. Tarval]

As per Eric's suggestions previously, I've been playing around with
some code for AM signals. 

Specifically, I've created a utility which will generate an AM signal 
from either a signal source (file/pipe/device), or it will generate a 
step-function signal automatically; and then it will take this signal 
and modulate it with a carrier wave (defaulting to 350 Hz, as per Eric's 
suggestion - but the carrier frequency can be changed by a command-line 
argument).

I've also created an AM demodulator, to demodulate any signal fed into it.

And, to top it off, I've hacked together a GUI which will display
not only the signal, but the power-spectrum as well. Sort of like 
an oscilloscope graph. From the power-spectrum you can see the side-bands 
for the modulated signal, as well as the frequencies of the demodulated
signal.

The one thing sorely missing is a low-pass filter; so the demodulated output
isn't clean right now, though the power-spectrum is still interesting.
But this exercise has served it's purpose for me for now; namely, as a 
learning experience to become more familiar with what's involved here. 

The downside is that it's written in C, and so it isn't immediately useable
with the pspectra code (which, of course, is the obvious next step).
But I've found these simple programs to be more easily understood than
all of the pspectra code.

At any rate, I've learned enough with it for now; and am moving on 
towards doing something similar with the pspectra code (though perhaps
not the GUI - we shall see).

Since I found these utilities of use, I thought that I'd make the offer 
to publish them. If anyone else wants a copy, just let me know.

Btw, Eric - thanks for your suggestions. Following them  was a great 
learning experience.

Best Regards,

        -ben-