AM Stereo (C-QUAM) Transmitter

I have finished work on a CQUAM https://en.wikipedia.org/wiki/C-QUAM
transmitter in GNURadio. CQUAM was among many competing standards for
Stereo AM radio, and is still in use around the world. I didn’t see much
fo
anything online about AM/AM Stereo modulation, so I figured I’d give it
a
go. Maybe someone could find some use out of it.

The GRC is available on Pastebin http://pastebin.com/VbbpRpM6. No
outside
blocks or modules required.

It takes input from a fifo called ‘/tmp/play’ and in my setup, it reads
my
mpd stream through mpg123, which is then sent through the Stereo Tool
audio
processor like so:

mpg123 -s http://127.0.0.1:8000 | ./stc - - -s mw.sts > /tmp/play

Once this is going, you run the flowgraph and it will dump its output to
output.wav. You can use hardware audio inputs, but I noticed with JACK,
there was a horrible delay between the stereo and mono portions of the
signal.

Not much to this graph really, works in SoDiRa’s CQUAM decoder, and I am
working on a receiver at the moment to test it fully. It has an 10Khz
filter, but if you’re putting this on the air, it is always best to have
an
external filter as well. :slight_smile:

Let me know how it works for you. Have fun.

  • Jordan

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