Re: [time-nuts] Time Signals on TV signals
Unfortunately cesium passthru went away with the advent of the use of frame synchronizers to receive the network signal and then re-clock it to match the local sync generator phase and frequency. The FCC requirement for the color burst signal (3.579545 MHz) is plus/minus 1 Hz... and you can certainly do better than that with most rudimentary oscillators. So, the phase stability of your local network affiliate is only as good as their local sync generator... Some stations do have sync generators with 10MHz EXT REF capability, allowing use of GPS or stabilized oscillators for that input... 73, Don, W4WJ In a message dated 5/25/2009 1:14:45 P.M. Central Daylight Time, hmur...@megapathdsl.net writes: Why did TV stations stop broadcasting time signals? HDTV requirements? One thing that may be relevant Many years ago, all the TV sources were kept in sync so there wasn't any glitch when they switched feeds. The sync timing was distributed from at atomic clock at network headquarters. The time of day probably piggybacked on that. I remember an old NBS booklet describing it. That was back in the late 70s. (It's probably a valuable collectors item now.) I think HP and NBS used to publish a table of delays for several major TV stations. Somebody on this list will probably recognize that description. The breakthrough that got around the timing requirement was frame buffers. (Thank Moore's law.) Could a cable company interfere with the time signals? Thanks for the laugh. :) Cable companies do all sorts of strange things. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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. **A Good Credit Score is 700 or Above. See yours in just 2 easy steps! (http://pr.atwola.com/promoclk/100126575x1222377034x1201454326/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072hmpgID=62bcd= MaystepsfooterNO62) ___ 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.
Re: [time-nuts] Time Signals on TV signals
Don, I think you might have dropped a zero there typing, They actually allow us +/- 10 Hz on burst. Best Regards, Mark Unfortunately cesium passthru went away with the advent of the use of frame synchronizers to receive the network signal and then re-clock it to match the local sync generator phase and frequency. The FCC requirement for the color burst signal (3.579545 MHz) is plus/minus 1 Hz... and you can certainly do better than that with most rudimentary oscillators. ___ 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.
Re: [time-nuts] Time Signals on TV signals
Hi Bill, I have no direct knowledge of the situation, but I have noticed that in my area the time signals seem to piggyback on the PBS stations, and in my area many of the PBS stations have ditched their analog signals earlier than the FCC mandate for digital TV. -Chuck Harris Bill Hawkins wrote: Aficionados of accurate time, I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to automatically sync time to a TV station. This worked fine until a few months ago. Now they are on manual time, but, of course, they drift. Tried to turn automatic time setting back on this morning. The screen says, This may take a few minutes. It still said that 10 minutes later, as the busy indicator continued to rotate through three spots. Gave up on automatic and asked the only group I know that might know. Why did TV stations stop broadcasting time signals? HDTV requirements? Could a cable company interfere with the time signals? Thanks, Bill Hawkins ___ 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.
Re: [time-nuts] Time Signals on TV signals
On 5/25/09 9:52 AM, Bill Hawkins b...@iaxs.net wrote: Aficionados of accurate time, I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to automatically sync time to a TV station. This worked fine until a few months ago. Now they are on manual time, but, of course, they drift. Tried to turn automatic time setting back on this morning. The screen says, This may take a few minutes. It still said that 10 minutes later, as the busy indicator continued to rotate through three spots. Gave up on automatic and asked the only group I know that might know. Why did TV stations stop broadcasting time signals? HDTV requirements? How does the time get transmitted? On the Vertical Interval? Which doesn't exist on HDTV, but I would imagine there's an equivalent sort of time code on the digital data stream (if only to allow multiple streams to be sync'd) Could a cable company interfere with the time signals? You betcha... There's no requirement on them to carry anything in any particular way. Transcoding, remodulation, resampling, not to mention that the basic transport layer from the headend to the user is not necessarily time synchronous.. Heck, they have trouble carrying emergency traffic properly, and they DO have requirements for that. And over the air signal is your best bet. Jim ___ 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.
Re: [time-nuts] Time Signals on TV signals
Why did TV stations stop broadcasting time signals? HDTV requirements? One thing that may be relevant Many years ago, all the TV sources were kept in sync so there wasn't any glitch when they switched feeds. The sync timing was distributed from at atomic clock at network headquarters. The time of day probably piggybacked on that. I remember an old NBS booklet describing it. That was back in the late 70s. (It's probably a valuable collectors item now.) I think HP and NBS used to publish a table of delays for several major TV stations. Somebody on this list will probably recognize that description. The breakthrough that got around the timing requirement was frame buffers. (Thank Moore's law.) Could a cable company interfere with the time signals? Thanks for the laugh. :) Cable companies do all sorts of strange things. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
Re: [time-nuts] Time Signals on TV signals
The NBS published a booklet on constructing a device that could receive the sync signals and provide a reasonable secondary frequency standard. I still have that book around in some box. I should look for it. IIRC, the signal originated from a Cesium standard and was used to sync the color so MTM didn't have purple hair !! 73, Dick, W1KSZ -Original Message- From: Hal Murray hmur...@megapathdsl.net Sent: May 25, 2009 2:14 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Time Signals on TV signals Why did TV stations stop broadcasting time signals? HDTV requirements? One thing that may be relevant Many years ago, all the TV sources were kept in sync so there wasn't any glitch when they switched feeds. The sync timing was distributed from at atomic clock at network headquarters. The time of day probably piggybacked on that. I remember an old NBS booklet describing it. That was back in the late 70s. (It's probably a valuable collectors item now.) I think HP and NBS used to publish a table of delays for several major TV stations. Somebody on this list will probably recognize that description. The breakthrough that got around the timing requirement was frame buffers. (Thank Moore's law.) Could a cable company interfere with the time signals? Thanks for the laugh. :) Cable companies do all sorts of strange things. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
Re: [time-nuts] Time Signals on TV signals
The NBS published a booklet on constructing a device that could receive the sync signals and provide a reasonable secondary frequency standard. I still have that book around in some box. I should look for it. IIRC, the signal originated from a Cesium standard and was used to sync the color so MTM didn't have purple hair !! 73, Dick, W1KSZ http://tf.nist.gov/timefreq/general/pdf/237.pdf Long-Term Continental U.S. Timing System Via Television Networks http://tf.nist.gov/timefreq/general/pdf/469.pdf Nationwide Precise Time and Frequency Distribution Utilizing an Active Code Within Network Television Broadcasts Visit: http://tf.nist.gov/timefreq/general/publications.htm and search for title: television /tvb ___ 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.
Re: [time-nuts] Time Signals on TV signals
It appears that the time information is transmitted in line 21 of the analog TV signal. This is the same line that carries Close Captions in an analog signal. It further appears that PBS is the major carrier of these time signals. See : http://simson.net/ref/autoclock/Interface-June-01.pdf#search=%27PBS%20time%20signal%20auto%20VCR%20set%27 This may explain why you are having problems. I do not know how this is handled in the DTV world. We translate line 21 captions to CEA-608 and CEA-708 captions for out DTV transmissions. See: http://ncamftp.wgbh.org/DTV/CEA%20test%20material/Iteration_1/It1.2ReadMe.pdf This explains a little about the conversion of analog line 21 to DTV captions. It is possible that you can set your recorder to read 608 captions? Hope this helps. 73 Glenn WB4UIV CE WCIV TV At 12:52 PM 5/25/2009, Bill Hawkins wrote: Aficionados of accurate time, I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to automatically sync time to a TV station. This worked fine until a few months ago. Now they are on manual time, but, of course, they drift. Tried to turn automatic time setting back on this morning. The screen says, This may take a few minutes. It still said that 10 minutes later, as the busy indicator continued to rotate through three spots. Gave up on automatic and asked the only group I know that might know. Why did TV stations stop broadcasting time signals? HDTV requirements? Could a cable company interfere with the time signals? Thanks, Bill Hawkins ___ 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.
Re: [time-nuts] Time Signals on TV signals
I think you're talking about the VITC, which is on lines 19 and 20 (so you get it on both fields with interlacing). VITC carries hour/minute/second/frame (same as LTC), but I don't know if it's program time (since start of program) or real time). There's a bunch of flavors of vertical interval time code, too.. Some put different info on each line, and use up to 4 lines. And don't forget the complexities introduced by 3/2 pulldown. As for what's actually broadcast (as opposed to put on a VTR or distributed in the editing suite) that's a whole 'nother ballgame. On 5/25/09 2:07 PM, Glenn Little WB4UIV glennmaill...@bellsouth.net wrote: It appears that the time information is transmitted in line 21 of the analog TV signal. This is the same line that carries Close Captions in an analog signal. It further appears that PBS is the major carrier of these time signals. See : http://simson.net/ref/autoclock/Interface-June-01.pdf#search=%27PBS%20time%20s ignal%20auto%20VCR%20set%27 This may explain why you are having problems. I do not know how this is handled in the DTV world. We translate line 21 captions to CEA-608 and CEA-708 captions for out DTV transmissions. See: http://ncamftp.wgbh.org/DTV/CEA%20test%20material/Iteration_1/It1.2ReadMe.pdf This explains a little about the conversion of analog line 21 to DTV captions. It is possible that you can set your recorder to read 608 captions? Hope this helps. 73 Glenn WB4UIV CE WCIV TV At 12:52 PM 5/25/2009, Bill Hawkins wrote: Aficionados of accurate time, I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to automatically sync time to a TV station. This worked fine until a few months ago. Now they are on manual time, but, of course, they drift. Tried to turn automatic time setting back on this morning. The screen says, This may take a few minutes. It still said that 10 minutes later, as the busy indicator continued to rotate through three spots. Gave up on automatic and asked the only group I know that might know. Why did TV stations stop broadcasting time signals? HDTV requirements? Could a cable company interfere with the time signals? Thanks, Bill Hawkins ___ 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. ___ 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.
