# AM Stereo (C-QUAM) Transmitter

**URL:** <https://www.ruby-forum.com/t/am-stereo-c-quam-transmitter/234785>\
**Category:** GNU Radio\
**Created:** [June 26, 2014, 9:26pm UTC](https://www.ruby-forum.com/t/am-stereo-c-quam-transmitter/234785 "2014-06-26T21:26:46Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [June 26, 2014, 9:26pm UTC](https://www.ruby-forum.com/t/am-stereo-c-quam-transmitter/234785/1 "2014-06-26T21:26:46Z")

</div>

I have finished work on a CQUAM [https://en.wikipedia.org/wiki/C-QUAM](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](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](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