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From: bill@videovax.UUCP (William K. McFadden)
Newsgroups: net.audio
Subject: Re: Can normal TV's be modified for stereo?
Message-ID: <1460@videovax.UUCP>
Date: Thu, 10-Oct-85 12:16:47 EDT
Article-I.D.: videovax.1460
Posted: Thu Oct 10 12:16:47 1985
Date-Received: Mon, 14-Oct-85 03:50:40 EDT
References: <1664@druxu.UUCP>
Reply-To: bill@videovax.UUCP (William K. McFadden)
Organization: Tektronix, Wilsonville OR
Lines: 35
Summary: 

In article <1664@druxu.UUCP> tlz@druxu.UUCP (ZrustTL) writes:
>1.  Is there anything that would prevent the addition of a "black
>    box" MTS stereo decoder to the audio circuits of a standard TV
>    (or is the encoding filtered out in the IF stages)?

Most TVs filter out the MTS subcarriers at the FM detector, but you can
still pick it up at the IF stages.  There is one company (the name escapes
me at the moment) that has developed an MTS receiver that has a sensitive
RF probe that you can attach to the outside of the TV set or near the IF strip
on the inside.  It relies on leakage from the IF section to pick up the signal.
this would let you rely on the TV's tuner only for channel selection.

>2.  If (1) is possible, does anyone know how to do this? Information
>    on IC part numbers, schematics, etc. appreciated.

Building your own decoder would be difficult because of the tolerances involved
and the lack of support ICs.  Probably within a year or two we will see
one- or two-chip MTS decoders.  I would wait until they become available before
attempting to build my own decoder.  (Besides, most TVs would have to be
modified to achieve the wide audio bandwidth required by MTS.)

>I think this sort of thing would be a rather entertaining project.
>The benefits of stereo TV alone certainly don't justify the effort
>and buying a new TV soley for  it's stereo capability is really insane!
>Nor do I want to but the Radio Shack stereo TV tuner since it defeats
>the convenience of remote control.
>I am totally unfamiliar with the encoding scheme used and thought this
>would be a good place to start.  Thanks.

See the article I posted to net.ham-radio a few days ago.  It explains how
stereo TV works.  Or, if you want me to mail you a copy, let me know.
-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-594  Beaverton, OR  97077
UUCP: ...{ucbvax,ihnp4,uw-beaver,decvax}!tektronix!videovax!bill
GTE:  (503) 627-6920        "How can I prove I am not crazy to people who are?"