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