[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 
synchronized hourly.
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 
>>> powered
>>> 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.  ...
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      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

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