From: Dave Tweed <pic@dtweed.com>
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Date: Thu, 26 Nov 2020 07:37:52 -0800
Subject: Re: [OT] Hyperikon Retrofit LED Tubes Without Ballast and
 fluorescent	lamps and TV!
Thread-Topic: [OT] Hyperikon Retrofit LED Tubes Without Ballast and
 fluorescent	lamps and TV!
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Harold Hallikainen wrote:
> NTSC television is interesting! It's described at
> http://mai.hallikainen.org/org/FCC/FccRules/2021/73/682/ . Prior to color=
,
> the field rate was indeed 60 Hz, the power line frequency, to avoid
> rolling "hum bars." With color, it appears everything is based on a
> precise 5 MHz with the chroma subcarrier being 5 MHz * 68/88.

That would be 3.863636 MHz, not even close to the correct value.

Jim wrote:
> The color burst frequency is 3.579545 Mhz.

The exact math is 30*525*455/2/1.001 =3D 3.579545e6 Hz

30 frames per second (60 fields)
525 lines per frame
455/2 cycles per line

The factor of 1.001 was chosen to make the sound subcarrier (fixed at 4.5 M=
Hz
for backward compatibility) an integer multiple (286x) of the horizontal li=
ne
rate (15734.266 Hz), which reduced the effects of interference between soun=
d
and both the Y and chroma components of the video.

-- Dave Tweed
--=20
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