16 Dec
2011
16 Dec
'11
8:45 a.m.
Christian Kennedy wrote:
RS-170a was referred to as "compatible"
because in theory it
didn't modify the definition of the television system but it actually
did with the field refresh frequency being changed from 60Hz to
59.94Hz in order to avoid stationary dot patterns that could result
from the difference frequency between the existing sound and new
color carriers.
It would have been better (IMHO) to shift the sound subcarrier frequency
by 0.1%, and keep the scan rate the same. None of the existing
receiving equipment (televisions) of the day had a precise enough sound
demodulator that this would have made any difference whatsoever. I told
that the FCC wouldn't let them shift the sound carrier, but I have no
idea why. The result is the 0.1% shift in the scan rate, which resulted
in the need for really awkward and inconvenient stuff like drop-frame
time code.
Nevertheless, I think that RCA and the second NTSC did some of the most
amazing and underappreciated engineering of the twentieth century.
Eric