Calibration Of Electronic Equipment In The Home Workshop
On Thu, 01 Mar 2007 16:32:18 -0600, clifto Gave us:
Bud-- wrote:
I believe the color subcarrier in a color TV is phase locked to the
transmitted signal and, for network studio transmissions, is derived
from a cesium clock. From what I have read it is more accurate than WWV
and doesn't require extra equipment other than a TV displaying an image
with a studio source. Frequency is 3.579545 MHz.
I've seen that discussed elsewhere, and although it would take me a week
to find the particulars, (1) the frequency can be off as much as 10 Hz
by FCC standards, (2) from what I've read it's frequently off by more
than that, even on network feeds, (3) IIRC they don't even use the good
clocks on the networks any more, (4) NIST clocks are going to be a couple
of orders of magnitude better than the best a network would buy for the
purpose of meeting FCC regulations, (5) IIRC the frequency should
actually be 3,579,545.454545454545..... Hz, and (6) Doppler shift on
the incoming television signal could potentially cause the subcarrier
frequency to vary up and down.
So there!
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