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From: kludge@grissom.larc.nasa.gov ( Scott Dorsey)
Newsgroups: sci.electronics
Subject: Re: SCA Tuner
Message-ID: <1991Apr16.142257.739@news.larc.nasa.gov>
Date: 16 Apr 91 14:22:57 GMT
References: <1991Apr12.195637.25132@uncecs.edu> <12780002@hpuplca.nsr.hp.com>
Sender: news@news.larc.nasa.gov (USENET Network News)
Reply-To: kludge@grissom.larc.nasa.gov ( Scott Dorsey)
Organization: NASA Langley Research Center
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Jeff Gruszynski writes:
>	Primary SCA is an FM signal @ 67KHz w/ 15KHz Max Deviation sitting 
>above (frequency wise) the 38KHz L-R DSB signal.  I seem to remember *old* 
>National Semiconductor Linear databooks having an SCA application example 
>on the LM565 entry.  I also seem to remember SCA being covered by the ECPA.
>(i.e. You're not supposed to listen).  Anyone with a better memory out
>there?

   Actually, it's illegal under the ECPA to listen to any subcarriers, 
because they are encrypted communications.  I suppose this goes for SCA
services.  It also applies to television audio and to FM stereo, so I think
that we can all get together and agree that the ECPA is worthless and
unenforceable.
   In a more happy vein, the latest Signetics Linear databook also has an
SCA decoder as one of the example circuits listed for one of their PLL
detectors.  It would also be fairly easy to use one of the FM stereo decoder
chips to do it, by using a tank circuit tuned to 38 instead of 19 KC.
   Anyone need some pentagrid converters?
--scott