Article View: sci.electronics
Article #9679Re: video chroma circuit
From: Mark Zenier
Date: Sat, 19 Jan 1991 04:43
Date: Sat, 19 Jan 1991 04:43
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1329 bytes
In article <1991Jan17.192816.23881@batcomputer.tn.cornell.edu>, gaarder@batcomputer.tn.cornell.edu (Steve Gaarder) writes: > >In article <767@ssc.UUCP> markz@ssc.UUCP (Mark Zenier) writes: > >>Does anyone know the reason they picked 3.579545... Mhz for the > Actually, it was done to make deriving those frequencies from the 3.579545 > master easier. A the time, frequency division was done by syncronizing > an oscillator, which was fine for small divisors but impractical for large > ones. Thus a division ratio was chosen that could be factored completely > into small numbers. (Divide the burst by 13, 5, and 7, then double it, to > get the horizontal frequency) Ok, and 5 Mhz divided by 8 and 11 then multplied by 7 then 9 is 3.579545... Has anyone seen any design rationale published by the NTSC. Ancient history, electronic style. markz@ssc.uucp
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!rutgers!bellcore!uunet!pilchuck!ssc!markz From: markz@ssc.UUCP (Mark Zenier) Newsgroups: sci.electronics Subject: Re: video chroma circuit Message-ID: <791@ssc.UUCP> Date: 19 Jan 91 04:43:56 GMT References: <767@ssc.UUCP> <14501@milton.u.washington.edu> <38104@cup.portal.com> <1991Jan17.192816.23881@batcomputer.tn.cornell.edu> Distribution: usa Organization: SSC, Inc., Seattle, WA Lines: 15