Hal Murray (hmurray@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

Hello all...
 
 
One limitation, back in the day, when the network
signal was being passed thru to the local markets...
 
Many stations used a frame sync to time the network
signal to the local house signal.  In other words the
network reference was stripped and retimed to the
house so as to avoid picture roll during switching
transitions between local and network programming.
 
So that meant that the local and network signals were
locked to the local sync generator which used a
fairly stable TCXO, not cesium or Rb.
 
Other stations would trim their local oscillator to
match the network phase without the need for a
frame sync.  This meant that someone was responsible
for monitoring how their local oscillator was tracking
against the network.
 
I spent over 35 years at WTVJ in Miami and over
the years we had an inventory of over 40 frame
syncs to lock remote feeds to house sync.
 
73
Don
W4WJ 
 
In a message dated 3/30/2018 4:54:36 PM Central Standard Time, fgrosz@otiengineering.com writes:

 
Hal Murray (hmurray@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

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.