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From: cmcmanis@sun.uucp (Chuck McManis)
Newsgroups: sci.electronics
Subject: Re: TV MTS Stereo decoding
Message-ID: <18204@sun.uucp>
Date: Wed, 6-May-87 16:18:48 EDT
Article-I.D.: sun.18204
Posted: Wed May  6 16:18:48 1987
Date-Received: Sat, 9-May-87 02:00:51 EDT
References: <4822@jhunix.UUCP>
Distribution: na
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 26
Keywords: demultiplexing
Summary: Plus it is dbx companded

In article <4822@jhunix.UUCP>, ins_aeas@jhunix.UUCP (Earle A. Sugar) writes:
>     Does anybody have the details of how MTS stereo is multiplexed and
> impressed on the VHF carrier?  What I am interested in in building my
> own decoder to connect to my stereo and TV.  Can I just put a normal
> FM stereo decoder chip in the normal audio
> signal from the TV tuner , and feed the output through the phono inputs
> on my stereo?  Or is there more to it (probably)?

There was a fairly complete 2 part article in Modern Electronics about
how MTS Stereo was achieved. Basically it used the standard trick of 
modulating the channels that FM stereo does R+L and R-L on the carrier
so regular TVs get mono and by splitting the R-L channel which is
modulated by a carrier to put it out of the TVs 'Audio' range you
can derive the separate R and L channels. The biggest difficulty is
that it is also companded using a dbx (tm somebody I'm sure) scheme
to increase the quality of the high end given the limited bandwidth.
If you have a 'stereo ready' TV like me then the manufacturer was 
nice enough to pull the audio out to a connector in the back that
hasn't gone through the standard low pass filter (which removes the
other stuff). Also note that the equipment in some Cable TV vendors
strips this off anyway (being old equipment that is trying to 'clean
up' the audio channel).
-- 
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses. But you knew that, didn't you.