[Discuss-gnuradio] AM Stereo (C-QUAM) Transmitter.

I have finished work on a CQUAM 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. 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. :)

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

- Jordan