[time-nuts] Using digital broadcast TV for timing?
jerryfi_99 at yahoo.com
Thu Feb 9 01:36:59 UTC 2012
Thanks Bob. I haven't kept up on TV broadcast standards & methods, obviously. It might be interesting (for the curiousity challenged) to pull out the color osc signal and compare to another accurate source (ie GPS) for live broadcasts. While delayed, I would think that the signal freqs would still need to be maintained... hmmm, maybe not... interesting science project... anyone? anyone? ;-)
> From: Bob Camp <lists at rtty.us>
> To: jerryfi <jerryfi_99 at yahoo.com>; Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Sent: Wednesday, February 8, 2012 4:43 PM
> Subject: Re: [time-nuts] Using digital broadcast TV for timing?
> 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
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