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? ;-)
Jerry ________________________________ > From: Bob Camp <[email protected]> > To: jerryfi <[email protected]>; Discussion of precise time and frequency > measurement <[email protected]> > 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 <[email protected]> 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
