Quote:
Originally Posted by Bob Olhsson  I once had a fascinating conversation with an old Ampex engineer. It seems the whole thing was never really necessary. What happened was that NTSC color was rolled out running on a 60 Hz. clock exactly like B&W. At the last minute some people at Ampex who were researching video recording technology noticed bars running through the B&W picture of a color transmission. The FCC went into a panic and quickly figured out that pulling the crystals down .1% got rid of the problem. A few weeks later it was discovered only to be a problem with crystal-controlled lab monitors and not ordinary TV sets.
But it was too late... |
I am not going to say that the Ampex engineer lied to you, but I read a conflicting account of this. If you go to
my website and read the Timecode PDF, you will find this.
The argument when color was developed was that the frequency of
the color subcarrier would create beating with the sound subcarrier that
would be visible on some black and white television sets. The sound
carrier, however, is frequency modulated. Therefore, beating would have
only occurred at a specific frequency. A GE engineer determined that if
the frame rate was dropped by .1% (from 30 to 29.97), that the beating
would be reduced, and compatibility would be maintained (Lehrman 220).
As a result of this change, 60Hz AC cannot leak into a video signal, or “bars
appear to roll through the picture every 17 seconds” (Schubin 29).
Again, I'm not saying the Ampex engineer doesn't know what he's talking about, but that's how I understood the issue. If this is going to be a sticky, perhaps we should work on figuring out if the truth is somewhere in-between or more towards one or the other.