29 May
2010
29 May
'10
5:13 a.m.
I wrote:
> From monochrome to color, all the video timings
> were adjusted by a factor of 1000/1001, to minimize interference between
> the chroma and the sound carrier. It seems like it would have been
> better to keep the video timing and move the sound carrier up by
> 1001/1000, but purportedly the FCC didn't like that idea, even though
> receivers of the day wouldn't have noticed.
>
Randy Dawson wrote:
With sound at 4.5, you are suggesting they move it up
a bit, and make the channel wider?
The days of spectrum space, 6 MHz wide for 1 TV broadcast are all now all gone.
Sound is at 4.5 MHz with a maximum deviation of +/- 25 kHz, so it is
from 4.475 to 4.525. Increasing the sound carrier
frequency by a
1001/1000 ratio to 4.5045 MHz would have made the range 4.4795 to
4.5295. That wouldn't have necessitated making the 6 MHz channel any
wider; it wouldn't even eat into the 250 kHz guard band of the next
channel. But it would have kept the 30Hz frame rate and thus avoided a
lot of madness like drop-frame timecode.
Best regards,
Eric