[time-nuts] NTP Clock suggestions?
Chuck Forsberg WA7KGX N2469R
caf at omen.com
Wed May 29 20:46:34 EDT 2013
One station I worked for in the 60s had a Western Union clock that was
If you watched it you could see the hands twitch at the top of the hour.
On 05/28/2013 05:04 PM, Al Wolfe wrote:
> I actually built a contraption like this back in the 1970's. As
> chief engineer at a couple of automated radio stations, I was tasked
> with keeping the network-joiner clocks accurate. It sounded really
> sloppy to have dead air or to up-cut the network. These clocks were 60
> htz synchronous motors that ran cam switches. Real PITA to adjust.
> Unfortunately, the utility power drifted up and down frequency wise, a
> few seconds a week. Long term was pretty good, though.
> I built a 10 mhz crystal oscillator and divided it down to 50 htz.
> with a string of 7490 decade dividers. Then built a 600 htz VCO out of
> a pair of 7400 NAND gates biased linearly. Divided the 600 by 12 with
> a 7492 and PLLed the 50 htz results with the precision 50 htz to
> control the 600 htz. Then divided the 600 by 10 in another 7490 to get
> 60 htz. Low passed this 60 htz square wave so it kind of looked like a
> sine wave and drove a small PA amplifier (pair of 6L6's I think.) This
> drove a 6.3 V filament transformer backwards to supply the 120 VAC to
> power the synchronous clock motors as well as some wall clocks.
> A kluge but it worked great. Every one was happy, the owner, the
> GM, the PD, and me because they got off my back about sloppy timing
> with the net joiner. About once a month or so I would fire up the old
> SP600 in the rack and check zero beat of the 10 mhz timebase against
> WWV with Lissijous figures on an oscilloscope. (Used the VFO of the
> SP600 do drive a cathode follower into a mixer so the the scope was
> looking at the low IF frequency. Zero beat was very obvious and the
> stability of the receive was not an issue.)
> This thing ran fine for at least ten years. The stations changed
> formats so they didn't need it any more. Probably wound up in a dumpster.
> Al, retired (A.K.A. K9SI)
>> albertson.chris at gmail.com said:
>>> OK, the LOWEST cost option I can think of for driving an analog
>>> clock with
>>> millisecond accuracy. Buy a normal AC powered clock that uses a
>>> synchronous AC motor that runs off the 60Hz AC power, not a battery
>>> clock. Then have your NTP disciplined computer generate a 60Hz
>>> audio sine
>>> wave. Amplify the sine wave to 12 volts then use a small 12:120 volt
>>> transformer to step up to 120VAC. ...
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
Chuck Forsberg WA7KGX caf at omen.com www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430
More information about the time-nuts