[time-nuts] Using digital broadcast TV for timing?

jerryfi 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?
> Hi
> 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.
> Bob

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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