Alan,

I believe the subcarriers you mention are the HDRadio sideband. I've tried decoding this band but have been unable so far - it seems that iBiquity holds their proprietary standards close and I guess the community hasn't yet figured out how to decode it. If anyone is aware of an approach to decoding HDRadio, I'd love to know.

http://en.wikipedia.org/wiki/HD_Radio

Ethan


On Sun, Mar 17, 2013 at 10:48 AM, Alan Corey <alancorey@yahoo.com> wrote:
This might be a better question for the Gnuradio list, but for years I've known that some broadcast FM stations actually transmit a second audio program which is somehow modulating a subcarrier in the main transmission.  It probably carries mostly elevator music type junk but is rumored to be commercial-free (a rare thing in the US!).  I remember seeing dedicated receivers advertised for this, but never actually bought one because I wasn't sure it was active in my area.  These date back to Lafayette Electronics days I think and ever since so 40 years or more.

I've noticed (in SdrSharp) that on some FM stations I can see what look like they might be subcarriers on either side of the main signal.  Anyone decoded those?

  Alan
 
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