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

[paul swed]

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 <timenutstan at 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 <paulswedb at 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_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?
> > > > Message-ID:
> > > >     <
> > 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
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