Re: [time-nuts] Using digital broadcast TV for timing?
the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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. ___ 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] Using digital broadcast TV for timing?
Does anyone know if ABC used Cesium or just Rubidium standards? I have the Tracor 304SC shown in this URL: http://www.bdairfield.com/stan/time-nuts/Tracor-304SC/IMG_4216.JPG I assume the SC in the model number stands for the color subcarrier frequency for NTSC: 3.579545 MHz. The boards seem to be mostly hand wired on turret pins, so I don't think they made very many. I usually try and clean up front panels and remove non-manufacturer stickers, but I thought the ABC New York, Rubidium 1 and ADJ May 21 84 were cool, so the stickers stayed. Under the top cover is a tag that says: Model 304-SC S/N 127 Frequency relative to USFS -300 X 10 ** -10 DATE 10-11-68 The front panel has a 5 MHz output, while the back has a 3.58 MC output. I'm told this unit no longer works. KO4BB does not have the manual on his site, if you know where one is, send me a link off list. If some folks know more about the history of network broadcast color subcarrier frequency standards, I think it's an interesting subject that would be worth hearing more about. Stan On Wed, Feb 8, 2012 at 7:07 PM, paul swed paulsw...@gmail.com wrote: All gone these days in the US. Indeed I can speak to the CBS network it was driven by CS references in the 80s and 90s. I used CBS for aligning my references Xtal oven oscillators that were never ever turned off in a large facility that uplinked all 8 CBS regions and 22 other cable networks. Unfortunately few could get to that color burst signal as devices called frame synchronizers came into play from the 80s to the 90s. They would strip off that burst and insert the local reference of generally much lower quality. As far as todays digital TV signals they can contain significant jitter. But its actually trickier then that and I honestly have to say I am not sure that you might not be able to get something useful. Several interesting points. Many of the television transmitters do use GPS referenced sources. Its an interesting exploration. I simply don't have the time though. Regards Paul WB8TSL On Wed, Feb 8, 2012 at 7:38 PM, jerryfi jerryfi...@yahoo.com wrote: A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https
Re: [time-nuts] Using digital broadcast TV for timing?
Stan By gosh that really is an old one. ABC very well could have been driven by a Rb ref. Though as I mentioned CBS was CS. So a bit hard to believe ABC and NBC were not. But I really simply do not remember. There had been a time when the networks were used for freq dissemination and thats why at least CBS had the CS. An alternate thought could be that it came from a local owned an operated station. And it was adjusted to the network. Some inside pixs would be pretty neat top see. Like you I chose to leave the USNO sticker on my sad but semi operational CS reference. Regards Paul WB8TSL On Mon, Feb 20, 2012 at 7:48 PM, Stan Searing timenuts...@gmail.com wrote: Does anyone know if ABC used Cesium or just Rubidium standards? I have the Tracor 304SC shown in this URL: http://www.bdairfield.com/stan/time-nuts/Tracor-304SC/IMG_4216.JPG I assume the SC in the model number stands for the color subcarrier frequency for NTSC: 3.579545 MHz. The boards seem to be mostly hand wired on turret pins, so I don't think they made very many. I usually try and clean up front panels and remove non-manufacturer stickers, but I thought the ABC New York, Rubidium 1 and ADJ May 21 84 were cool, so the stickers stayed. Under the top cover is a tag that says: Model 304-SC S/N 127 Frequency relative to USFS -300 X 10 ** -10 DATE 10-11-68 The front panel has a 5 MHz output, while the back has a 3.58 MC output. I'm told this unit no longer works. KO4BB does not have the manual on his site, if you know where one is, send me a link off list. If some folks know more about the history of network broadcast color subcarrier frequency standards, I think it's an interesting subject that would be worth hearing more about. Stan On Wed, Feb 8, 2012 at 7:07 PM, paul swed paulsw...@gmail.com wrote: All gone these days in the US. Indeed I can speak to the CBS network it was driven by CS references in the 80s and 90s. I used CBS for aligning my references Xtal oven oscillators that were never ever turned off in a large facility that uplinked all 8 CBS regions and 22 other cable networks. Unfortunately few could get to that color burst signal as devices called frame synchronizers came into play from the 80s to the 90s. They would strip off that burst and insert the local reference of generally much lower quality. As far as todays digital TV signals they can contain significant jitter. But its actually trickier then that and I honestly have to say I am not sure that you might not be able to get something useful. Several interesting points. Many of the television transmitters do use GPS referenced sources. Its an interesting exploration. I simply don't have the time though. Regards Paul WB8TSL On Wed, Feb 8, 2012 at 7:38 PM, jerryfi jerryfi...@yahoo.com wrote: A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time
Re: [time-nuts] Using digital broadcast TV for timing?
On 02/10/2012 06:56 PM, Bob Camp wrote: Hi I suspect that if you went into the GPS jamming business that the mob of lawyers would be even more scary than the stuff being dropped on your antennas... Not even the US military could be that evil!!! If you attempts that total jamming approach then you are probably a state. There are a few states which actually do such jammings to telecom sats. I think they would not care what the lawyers says. I also think the US air force would care about their strategic assets being under continuous attack. Cheers, Magnus Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Thursday, February 09, 2012 4:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Using digital broadcast TV for timing? On 02/09/2012 07:21 PM, Chris Albertson wrote: On Wed, Feb 8, 2012 at 11:02 PM, Hal Murrayhmur...@megapathdsl.net wrote: Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. By went away, I meant locally, as be being jammed or spoofed. Possibly a car drives into a tunnel and then from the car's point of view GPS goes away. From a military point of view all it takes to knock out GPS is to suicide truck-bomb both ground control stations or simply jam the GPS uplinks so the stations are unable to send commands. But The question was more theoretical then practical. Let's assume that the physical safety of the ground control center is there, and just have a look at the jamming of up-links. Jamming the up-links would be a bit of a difficult task, since there is not one but several up-links, also you would need to high-energy jam all the birds as you would not know when they would get their commands. Add their capability of cross-link communication and ability to uphold a decent situation in autonav for ground station outage of up to 180 days. Oh, both uplink and cross-link is encrypted and fairly jam-resistant. Cross-link has nulls towards earth and only a half-decent gain in certain angles. All that comes out of public sources. It would take a bit of resources to do a global GPS outage, and to maintain it you would expose yourself over a long time such that you would be found and well, let's assume that your antennas will not take kindly to the things being dropped at it. Regional outages is much easier. Cheers, Magnus ___ 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.
Re: [time-nuts] Using digital broadcast TV for timing?
Hi I suspect that if you went into the GPS jamming business that the mob of lawyers would be even more scary than the stuff being dropped on your antennas... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Thursday, February 09, 2012 4:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Using digital broadcast TV for timing? On 02/09/2012 07:21 PM, Chris Albertson wrote: On Wed, Feb 8, 2012 at 11:02 PM, Hal Murrayhmur...@megapathdsl.net wrote: Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. By went away, I meant locally, as be being jammed or spoofed. Possibly a car drives into a tunnel and then from the car's point of view GPS goes away. From a military point of view all it takes to knock out GPS is to suicide truck-bomb both ground control stations or simply jam the GPS uplinks so the stations are unable to send commands. But The question was more theoretical then practical. Let's assume that the physical safety of the ground control center is there, and just have a look at the jamming of up-links. Jamming the up-links would be a bit of a difficult task, since there is not one but several up-links, also you would need to high-energy jam all the birds as you would not know when they would get their commands. Add their capability of cross-link communication and ability to uphold a decent situation in autonav for ground station outage of up to 180 days. Oh, both uplink and cross-link is encrypted and fairly jam-resistant. Cross-link has nulls towards earth and only a half-decent gain in certain angles. All that comes out of public sources. It would take a bit of resources to do a global GPS outage, and to maintain it you would expose yourself over a long time such that you would be found and well, let's assume that your antennas will not take kindly to the things being dropped at it. Regional outages is much easier. Cheers, Magnus ___ 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] Using digital broadcast TV for timing?
On Wed, Feb 8, 2012 at 11:02 PM, Hal Murray hmur...@megapathdsl.net wrote: Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. By went away, I meant locally, as be being jammed or spoofed. Possibly a car drives into a tunnel and then from the car's point of view GPS goes away. From a military point of view all it takes to knock out GPS is to suicide truck-bomb both ground control stations or simply jam the GPS uplinks so the stations are unable to send commands. But The question was more theoretical then practical. But this is time nuts. I think it's interesting to consider where we might get a second source of time or frequency frequency. How good is it? What does it cost? How much can amateurs do? Maybe something will work where GPS doesn't. I was going to try GPS in a big machine room but we didn't get that far. It didn't work in the adjoining office complex. I assume there was too much metal in the building. but EMI from all the local PCs probably didn't help much. -- 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. -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
On 02/09/2012 07:21 PM, Chris Albertson wrote: On Wed, Feb 8, 2012 at 11:02 PM, Hal Murrayhmur...@megapathdsl.net wrote: Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. By went away, I meant locally, as be being jammed or spoofed. Possibly a car drives into a tunnel and then from the car's point of view GPS goes away. From a military point of view all it takes to knock out GPS is to suicide truck-bomb both ground control stations or simply jam the GPS uplinks so the stations are unable to send commands. But The question was more theoretical then practical. Let's assume that the physical safety of the ground control center is there, and just have a look at the jamming of up-links. Jamming the up-links would be a bit of a difficult task, since there is not one but several up-links, also you would need to high-energy jam all the birds as you would not know when they would get their commands. Add their capability of cross-link communication and ability to uphold a decent situation in autonav for ground station outage of up to 180 days. Oh, both uplink and cross-link is encrypted and fairly jam-resistant. Cross-link has nulls towards earth and only a half-decent gain in certain angles. All that comes out of public sources. It would take a bit of resources to do a global GPS outage, and to maintain it you would expose yourself over a long time such that you would be found and well, let's assume that your antennas will not take kindly to the things being dropped at it. Regional outages is much easier. Cheers, Magnus ___ 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] Using digital broadcast TV for timing?
Maybe cell site transmissions are better? Raj The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
Hi Back in the late 90's Symmetricom made up some disciplined Rubidium's that ran off of cell towers. If you Google Timesource 2700 you can probably find a lot of information on them. Until people figured out what was in them, they were a great way to score a PRS-10 Rubidium (great phase noise) for very little money ($200 or so). The telcom companies used them for a while and ultimately scrapped a lot of them out. Rumor is that not all cell towers are as locked up time wise as they should be. The discipline obviously only works if they are. Even if you have a good tower today, there is no guarantee that it's locked tomorrow. GPS can drop out due to equipment issues and you will drift as the tower drifts. Bottom line, it's a solution that brings in a whole new set of problems. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Wednesday, February 08, 2012 6:01 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Using digital broadcast TV for timing? Maybe cell site transmissions are better? At least one company makes them. http://tinyurl.com/72j5e6n http://www.endruntechnologies.com/telecom-primary-reference-source.htm It's CDMA. I don't know much about cell phones, but I think that's the old protocol that will probably/eventually fade away. I don't know anybody who has worked with them. The advantage is that you can set them up in your machine room and don't need an outside antenna. (If your cell phone works there, this should work too.) I'd expect the time accuracy would be not as good as GPS. It would be off by the time-of-flight from the cell tower, 5 microseconds per mile. That's 5 microseconds per mile which is no problems unless you are a time-nut. (I don't know if the cell towers add more to that.) -- 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] Using digital broadcast TV for timing?
Hi These days the easiest solution might be to put an Ethernet device a few floors up (where you can see the sky) and haul packets on down to the bottom of the canyon. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Tuesday, February 07, 2012 9:01 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Using digital broadcast TV for timing? GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
A thought and an observation related to getting timing from broadcast DTV signals. BC DTV uses a scheme called 8VSB, which includes a pilot 'carrier' at the low frequency end of the signal. This is used to help the receiver lock to the TX so that the phase information can be accurately decoded. It seems to me that this might be a possible source of a useful frequency reference, although there is no guarantee that it is traceable to anything or even very accurate. The observation is that one of my local stations simulcasts the same programming in both 1080 and 780 formats, and when I switch from the 1080 channel to the 780, there is a very obvious 1 to 2 second delay in both the audio and video of the 780 format. These are being transmitted as separate streams on the same carrier. Definitely suggests that there is a lot of 'processing' and buffering going on while putting the complete bit stream together. Tom Holmes, N8ZM Tipp City, OH EM79 -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jerryfi Sent: Wednesday, February 08, 2012 7:38 PM To: time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gm ail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
All gone these days in the US. Indeed I can speak to the CBS network it was driven by CS references in the 80s and 90s. I used CBS for aligning my references Xtal oven oscillators that were never ever turned off in a large facility that uplinked all 8 CBS regions and 22 other cable networks. Unfortunately few could get to that color burst signal as devices called frame synchronizers came into play from the 80s to the 90s. They would strip off that burst and insert the local reference of generally much lower quality. As far as todays digital TV signals they can contain significant jitter. But its actually trickier then that and I honestly have to say I am not sure that you might not be able to get something useful. Several interesting points. Many of the television transmitters do use GPS referenced sources. Its an interesting exploration. I simply don't have the time though. Regards Paul WB8TSL On Wed, Feb 8, 2012 at 7:38 PM, jerryfi jerryfi...@yahoo.com wrote: A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
Thanks Paul. You and Bob Camp provided some good updates/info. It may present enough of a challenge/reward for someone to examine further. I'm with you on the available time front - too many other projects/commitments to pursue further myself. I'll be interested if Chris, or someone else, can make some headway though. Jerry AG6HH From: paul swed paulsw...@gmail.com To: jerryfi jerryfi...@yahoo.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, February 8, 2012 7:07 PM Subject: Re: [time-nuts] Using digital broadcast TV for timing? All gone these days in the US. Indeed I can speak to the CBS network it was driven by CS references in the 80s and 90s. I used CBS for aligning my references Xtal oven oscillators that were never ever turned off in a large facility that uplinked all 8 CBS regions and 22 other cable networks. Unfortunately few could get to that color burst signal as devices called frame synchronizers came into play from the 80s to the 90s. They would strip off that burst and insert the local reference of generally much lower quality. As far as todays digital TV signals they can contain significant jitter. But its actually trickier then that and I honestly have to say I am not sure that you might not be able to get something useful. Several interesting points. Many of the television transmitters do use GPS referenced sources. Its an interesting exploration. I simply don't have the time though. Regards Paul WB8TSL On Wed, Feb 8, 2012 at 7:38 PM, jerryfi jerryfi...@yahoo.com wrote: A bit off topic, but historically related back in the 70's, I tapped off the color burst oscillator in my TV (a Heathkit) to get a 3.579545 MHz (315/88 MHz) source to calibrate my homebrew frequency counter. The TV's color burst oscillator was phase locked to the color burst signal on the broadcast signal (which was on the back porch of the hori sync signals). Supposedly, the networks were locked to Cesium standards traceable to NBS for LIVE broadcasts, such as news and sports. Taped programs, of course, were not usable as an accurate source. In any case, that signal served my purposes at the time (providing a reference for calibrating my counter that was more accurate than anything else available to me). I'm not sure if, what, or where analog TV is still broadcast, but I think there are still a few stations (low power) around. You might still be able to use that signal, IF you can dig it out of your old analog TV. ;-) I do have analog tv's hooked up to my cable box - I suspect that live broadcasts would still have an accurate color burst, so maybe I think the other methods discussed here (ie, GPS) would provide easier and more reliable timing sources. ;-) Trying to locate the appropriate signal(s) in a digital TV today would be interesting. Just as a historical aside. Jerry Finn Santa Maria, CA Date: Tue, 7 Feb 2012 18:01:26 -0800 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Using digital broadcast TV for timing? Message-ID: cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
On Wed, Feb 8, 2012 at 7:48 PM, jerryfi jerryfi...@yahoo.com wrote: Thanks Paul. You and Bob Camp provided some good updates/info. It may present enough of a challenge/reward for someone to examine further. I'm with you on the available time front - too many other projects/commitments to pursue further myself. I'll be interested if Chris, or someone else, can make some headway though. OK if not DTV what other common signal that you could pick up without use of exotic equipment (so this entirely eliminates rotating neutron starts or pulsars) what else can you get that has decent timing other then GPS and CDMA. I'm not giving up on DTV yet. The video signal is compressed so it may be basically white noise but I bet it is wrapped in some transport like packets that are regular. In practice GPS works well but a question came up here What could you use if GPS went away?I said I bet there is some signal all around us that just happens to have precision timing embedded in it. Maybe DTV maybe it's direct broadcast TV. -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. On 02/08/2012 09:13 PM, Chris Albertson wrote: On Wed, Feb 8, 2012 at 7:48 PM, jerryfijerryfi...@yahoo.com wrote: Thanks Paul. You and Bob Camp provided some good updates/info. It may present enough of a challenge/reward for someone to examine further. I'm with you on the available time front - too many other projects/commitments to pursue further myself. I'll be interested if Chris, or someone else, can make some headway though. OK if not DTV what other common signal that you could pick up without use of exotic equipment (so this entirely eliminates rotating neutron starts or pulsars) what else can you get that has decent timing other then GPS and CDMA. I'm not giving up on DTV yet. The video signal is compressed so it may be basically white noise but I bet it is wrapped in some transport like packets that are regular. In practice GPS works well but a question came up here What could you use if GPS went away?I said I bet there is some signal all around us that just happens to have precision timing embedded in it. Maybe DTV maybe it's direct broadcast TV. -- Chris Albertson Redondo Beach, California ___ 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. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] Using digital broadcast TV for timing?
I'm not completely convinced that DTV has been eliminated as a source, but it would take some study (and discussions with the DTV providers). There may be something there. The problem you have is that so many (most, if not all) stable rf signal sources are derived from GPS today, so that in the EXTREMELY unlikely event that all (24+) GPS sats went off the air, many of those sources would all be affected to one degree or another. You might look at the Russian Glonass system, the European Gallileo system (which is only in prototyping stage), and possibly the Chinese Beidou NAVSATS. Gallileo and Glonass work similar to GPS, but Beidou is a different beast. There are receivers that use both GPS and GLONASS, but I don't have any direct experience with them. WWV (and related HF time signal sources) are an obvious alternative source. NIST operates WWV transmitters at 2.5, 5, 10, 15 and 20 MHz from Fort Collins, CO, and WWVH from Hawaii. These signals are locked to Cs standards. There are other HF time signals from Canada, etc, you might check out. Depending on what you want to do, you might just consider synchronizing a Rb, or a bank of Rb's to GPS. Then if GPS went away, the Rb's would free run for a considerable time. Considerable needs to be defined by your timing requirements, and duration, in the non-GPS environment. And then, of course, there are Cesium standards available, if you have deep pockets. Jerry Finn AG6HH From: Chris Albertson albertson.ch...@gmail.com To: jerryfi jerryfi...@yahoo.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, February 8, 2012 9:13 PM Subject: Re: [time-nuts] Using digital broadcast TV for timing? On Wed, Feb 8, 2012 at 7:48 PM, jerryfi jerryfi...@yahoo.com wrote: Thanks Paul. You and Bob Camp provided some good updates/info. It may present enough of a challenge/reward for someone to examine further. I'm with you on the available time front - too many other projects/commitments to pursue further myself. I'll be interested if Chris, or someone else, can make some headway though. OK if not DTV what other common signal that you could pick up without use of exotic equipment (so this entirely eliminates rotating neutron starts or pulsars) what else can you get that has decent timing other then GPS and CDMA. I'm not giving up on DTV yet. The video signal is compressed so it may be basically white noise but I bet it is wrapped in some transport like packets that are regular. In practice GPS works well but a question came up here What could you use if GPS went away? I said I bet there is some signal all around us that just happens to have precision timing embedded in it. Maybe DTV maybe it's direct broadcast TV. -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
Other than LightSquared, an event that made GPS go away would most likely eliminate most interest in ultra accuracy time keeping. But this is time nuts. I think it's interesting to consider where we might get a second source of time or frequency frequency. How good is it? What does it cost? How much can amateurs do? Maybe something will work where GPS doesn't. I was going to try GPS in a big machine room but we didn't get that far. It didn't work in the adjoining office complex. I assume there was too much metal in the building. but EMI from all the local PCs probably didn't help much. -- 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] Using digital broadcast TV for timing?
GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
You might be able to find the PCR clock at 90kHz, but.. PCR clocks are usually just decent oscillators, nothing special. GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
The DTV signal coding has a major problem in that it is not deterministic - they can't even synchronize the audio and video. There have been many workshops on this at the Audio Engineering Society conventions. I doubt there is any useable timing in it. David McGaw At 09:01 PM 2/7/2012, Chris Albertson wrote: GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? -- Chris Albertson Redondo Beach, California ___ 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] Using digital broadcast TV for timing?
On 2/7/12 6:01 PM, Chris Albertson wrote: GPS requires a good view of the sky, Hard to do in say the 7th floor of a 40 story building if you have no windows. I'm wondering about using the new digital TV signals for timing. I'm pretty sure there is time code in the signal and I'm pretty sure the bits are clocked at a very accurate rate. Also TV receivers are very easy to find and put hooks into. I'd bet the broadcast TV signal could be almost as good as GPS. Actually, no... because it's so easy to do frame buffering/time base correcting to fix anything. Back in the bad old days of analog everything, you needed really good sync and timing to make things like switchers and faders work. A time base corrector was wretchedly expensive, so you'd go to a lot of work distributing black burst around and syncing your tape machines, etc. The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? ___ 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] Using digital broadcast TV for timing?
albertson.ch...@gmail.com said: The plan is to try and phase lock a local oscillator and use a very long time constant on the loop filter. I bet the TV transmitters are locked to GPS and over a long enough time are as good as GPS. Also in many cities there are many TV transmitters, should be able to take advantage of that. Before I try some experiments anyone want to tell me why I'm wrong? In the old days, the whole TV network was locked to a cesium in network headquarters. I think it was back in the late 70s when a friend showed me a neat booklet from NBS (it wasn't NIST yet) that described using NBC (I think) to distribute time. I forget the details. It basically described where to look in the signal for the time-sync info. All the local stations needed it. HP did the calibration for the Silicon Valley area. Every month they would publish the delay from New York to HP. I think you could get to a ms or so. The main problem was that the phone company might reroute the signal. When did frame buffers arrive? They eliminated the need for stations to be in sync. That means that your local TV station might not be in sync these days. Then came digital TV and compression. That introduces variable display. I think it would be fun to find the time info on a local TV station and measure the offset to a local GPS. I'll bet it's not very good. -- 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.
