Marcus,
Here's what I found, with a google image search, there are some interesting images and discussions of the modulation techniques there with both block and flow diagrams.
This one seems very interesting and probably makes it similar to what might have to be done with gnuradio.
The basic idea behind the C-Quam modulator is actually quite simple. The output stage is an
ordinary AM modulator however; the carrier signal has been replaced by an amplitude limited vector modulator. Therefore, the limiter output is really a phase-modulated signal.
A standard AM receiver will detect the amplitude variations as L+R. A stereo receiver will also detect the phase variations and to extract L‑R. It will then process these signals to separate the left and right channels.
To enable the stereo decoder, a 25 Hz pilot tone is added to the L‑R channel.
Hope this helps.
Bruce
From: Marcus D. Leech <address@hidden>
To: address@hidden
Sent: Monday, March 24, 2014 5:11 PM
Subject: Re: [Discuss-gnuradio] AM Stereo TX? (Motorola C-QUAM)
On 03/24/2014 07:59 PM, Jordan Johnson wrote:
I have been Googling a good deal and have not come up with
much. I have done numerous projects with GNURadio, but while
I can throw together a wideband AM transmitter, I cannot
figure out the stereo portion. Based on what I know; it is
some kind of phase-modulated information.
Anyone know how to get started on a flowgraph, or maybe some
code examples?
Thanks. :)
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I don't think I've ever heard of anyone making this query before.
You should probably start with whatever public documents describe
the
Motorola system, and go from there.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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