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From: dsi@unccvax.UUCP
Newsgroups: net.video,net.analog
Subject: Re: MTS stereo decoder
Message-ID: <440@unccvax.unccvax.UUCP>
Date: Thu, 13-Feb-86 09:56:34 EST
Article-I.D.: unccvax.440
Posted: Thu Feb 13 09:56:34 1986
Date-Received: Sun, 16-Feb-86 05:00:57 EST
References: <218@catnip.UUCP>
Organization: UNC-Charlotte
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Xref: watmath net.video:2027 net.analog:686

> The current (March 1986) issue of Radio-Electronics magazine contains
> plans for a stereo tv decoder.  I was pleased as punch to see this, since
> 
> Here is the rub.  The circuit does not contain any noise reduction.
> Apparently, the compression technique used is proprietary to dbx, and
> the chips necessary to do it are available only to licenced OEMs.
> So, my question:
> 
>   - Is it worth building one of these?
>   - How noisy will it be without the dbx chips?

     Don't bother.  According to the National Association of Broadcasters
Engineering Handbook, Seventh Edition (just hot off the NAB press) the 
signal to noise ratio of the uncompanded BTSC subcarrier is roughly 20 dB
at 5000 Hz. Both wideband decibel linear companding AND sliding band 
equalisation is used; the result is not the same as DBX "B" system used
for consumer audio. 

     Get a real BTSC decoder if you want satisfactory stereo programme
service...

dya