[time-nuts] Using digital broadcast TV for timing?
lists at rtty.us
Thu Feb 9 00:43:49 UTC 2012
The whole cesium lock approach died back in the 90's. These days your local station buffers / retimes / reframes everything. If you are lucky they use a Rb for the timing.
On Feb 8, 2012, at 7:38 PM, jerryfi <jerryfi_99 at 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.chris at gmail.com>
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at febo.com>
>> Subject: [time-nuts] Using digital broadcast TV for timing?
>> <CABbxVHvb3SKzuMx+bDyKTtesGzuf2k5HSJWYpdKK+RQOArxRgA at 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 at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts