Hal Murray (hmur...@megapathdsl.net) said:
"Roughly 40 years ago, a friend showed me a NBS booklet describing a scheme
for distributing time via TV. I forget the details. It was a cooperative
project with one of the major networks. NBS published the propagation delays
which changed occasionally as the phone companies providing the underlying
links rerouted things.
This is an IEEE article from 1972 that looks like a good fit:
Nationwide Precise Time and Frequency
Distribution Utilizing an Active Code Within
Network Television Broadcasts
DAVID A. HOWE
https://www.researchgate.net/publication/3092613";
I was a TV Broadcast Engineer in the 70s. There were a number of
schemes for transmitting frequency standard information via the TV
signal. One used the VITS signal referenced above. Another used a
cesium standard to control the 3.58 MHz (actually 3.579545454... MHz)
color burst signal. There were several articles in the hobbyist
press at the time on using this for a standard. You had to be
careful to use a network program, however; most local station could
not afford a cesium reference for something like that. (Actually,
the station I worked for had one but it was used for controlling the
transmitter frequency. Long story). Now that analog TV has gone
away, so have these signals.
Francis Grosz
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