<html><body><div style="color:; background-color:; font-family:arial, helvetica, sans-serif;font-size:13px"><div><br>SCA is what I was thinking of, but this sounds more like overload. From my raw notes:<br><br> If I tune to 88.500 MHz I see signals about 88.3367 and 88.662<br>The upper one is 162 KHz away, the lower one 163. If I click on one I hear nothing.<br><br>The same is true of WAMC(?) at 90.300 with 90.138 and 90.465 so 162 and 165.<br><br>-----<br>I don't have a screen shot and I haven't seen it happen lately.<br><br> Alan<br><br></div><div>-----<br>Radio Astronomy - the ultimate DX<br></div><div> <br> <div>----- Original Message -----<br> > From: Robert Nickels <ranickel@comcast.net><br> > To: osmocom-sdr@lists.osmocom.org<br> > Cc: <br> > Sent: Sunday, March 17, 2013 12:32 PM<br> > Subject: Re: Broadcast FM subcarrier decoding?<br> > <br>> On 3/17/2013 9:48 AM, Alan Corey wrote:<br>>> I
can see what look like they might be subcarriers on either side of the <br>> main signal. Anyone decoded those?<br>> <br>> Hi Alan,<br>> <br>> Depending on where you live, there could be several subcarriers present. From <br>> your description I'm pretty sure you're referring to Sub Carrier <br>> Authorization (SCA) which has been mainly used for background music and an audio <br>> book reading service for the blind as well as other voice and data services. <br>> SCA uses 67 or 92 KHz subcarriers which can be seen on the composite FM signal. <br>> If you have a soundcard with sufficient bandwidth you can send the output of <br>> SDR# (in NBFM, 150 KHz mode) to another instance of SDR# *(sound card, DSB <br>> mode) using Virtual Audio Cable. My soundcard won't go high enough but <br>> here's a set of screen images from a system that can, where the various
<br>> elements on the upper side of the FM channel center are annotated: <br>> http://img208.imageshack.us/img208/5922/fmspectrum.png<br>> <br>> The RDS (Radio Data System) or RDBS in the US digital data channel is easily <br>> seen at 57 KHz, The level of all these subcarriers is much lower than the <br>> stereo pilot so you'll need a strong signal for decoding.<br>> <br>> 73, Bob W9RAN<br>> </div> </div> </div></body></html>