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Posting-Version: version B 2.10.1 6/24/83; site watmath.UUCP
Path: utzoo!watmath!dmmartindale
From: dmmartindale@watmath.UUCP (Dave Martindale)
Newsgroups: net.audio
Subject: Re: A minor nit regarding TV sweep, also service comments
Message-ID: <8216@watmath.UUCP>
Date: Wed, 4-Jul-84 13:04:08 EDT
Article-I.D.: watmath.8216
Posted: Wed Jul  4 13:04:08 1984
Date-Received: Thu, 5-Jul-84 00:26:49 EDT
References: <2943@rabbit.UUCP>
Organization: U of Waterloo, Ontario
Lines: 14

I'd like to pick a nit with jj's nit-picking.  The colour subcarrier
frequency is C = 3579545 Hz, +-10 Hz - this is picked, as he says, to
keep the sound and video from interfering with each other as much as
possible.  Then, the horizontal frequency H = C*2/455 which is about 15734 Hz.
This makes the colour subcarrier an odd multiple of half the line frequency,
reducing interference of the colour and luminance information (and giving
the best black&white picture).  Finally, the vertical frequency is H*2/525
(525 lines, 2:1 interlace) which is about 59.94 Hz.

But of course, terminals don't necessarily use exactly the same frequencies
that broadcast TV does.  As long as they use frequencies in the same
ballpark, they can use the same (cheap) TV parts in their monitors.
It's possible to build terminals that use ultrasonic horizontal frequencies,
but few manufacturers seem to do it.