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, fgr...@otiengineering.com writes:
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 _______________________________________________ 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. _______________________________________________ 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.