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History of 29.97



For those who may be interested, the underlying historical reason for the
shift of NTSC frequencies in 1952 was twofold, the result of testing
carried out by the NTSC committee in the course of its standardization effort:

1. It was determined desirable to frequency interleave color subcarrier and
the beat product of the color subcarrier and the sound carrier to reduce
the visibility of this beat in the picture of recievers of the time, and

2. It was deemed impractical to move the pre-existing 4.5 Mhz sound to
picture carrier offset because this would cause compatibility problems with
some existing b&w sets then in use. Therefore the color subcarrier
frequency had to be moved to meet the requirements of decision #1, and the
line, field and frame rates moved with it, as they were already frequency
interleaved.

Chuck Heuer
Click3X NYC



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