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Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!mcnc!unccvax!dsi
From: dsi@unccvax.UUCP (Dataspan Inc)
Newsgroups: net.video,net.analog
Subject: Re: Q-channel bandwidth
Message-ID: <150@unccvax.UUCP>
Date: Wed, 6-Mar-85 11:47:17 EST
Article-I.D.: unccvax.150
Posted: Wed Mar  6 11:47:17 1985
Date-Received: Sat, 9-Mar-85 10:44:10 EST
References: <146@unccvax.UUCP>, <304@petrus.UUCP>
Organization: UNC-Charlotte
Lines: 20
Xref: watmath net.video:1039 net.analog:190

a
     Shortly after my inane question, the reason for the narrow Q-bandwidth
was privately made known. As the I-channel is vestigial sideband suppressed
carrier AM, the frequency components from 500 kc to 1.5 mc will appear in
phase quadrature (all together now!) in the Q channel. The choppage of one
of the sidebands causes phase modulation of the other..... Oh well.

     Now, on the other hand, three RCA engineers described an adaptation of
NTSC that was fully compatible in the sense that their system could also receive
NTSC broadcasts. Both I and Q channels were extended to 1.8 mc bandwidth and
cancellation of the sound subcarrier (ala pilot cancellation in modern FM
receivers) was used. They didn't (dare ?) mention what the picture looked
like on a standard receiver although I suspect the narrow-chroma receiver
wouldn't even care in the least. It's in 1970-73 IEEE Transactions on Broadcast
Receivers (or something like that).

    Back to my sickly-green lettuce commercials

dya
.