Broadcast FM subcarrier decoding?
alancorey at yahoo.com
Thu Mar 28 02:19:40 UTC 2013
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.
Radio Astronomy - the ultimate DX
----- Original Message -----
> From: Robert Nickels <ranickel at comcast.net>
> To: osmocom-sdr at lists.osmocom.org
> 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:
> 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
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