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 <[email protected]> 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 <[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 > > > > > > > > > Date: Tue, 7 Feb 2012 18:01:26 -0800 > > > From: Chris Albertson <[email protected]> > > > To: Discussion of precise time and frequency measurement > > > <[email protected]> > > > Subject: [time-nuts] Using digital broadcast TV for timing? > > > Message-ID: > > > < > cabbxvhvb3skzumx+bdykttesgzuf2k5hsjwypdkk+rqoarx...@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 -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > 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. > _______________________________________________ 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.
