[time-nuts] Re: Power line timing -- setting a clock

[Larry McDavid]

Thank you, Walt, for reporting the time-inaccuracy of mains-synched 
clocks that I see. I'm glad you are far distant from me, and so you have 
data from a new location and generation utility.

I last set all my appliance and mains-synched clocks late on March 9, to 
advance the time for DST. I just checked and all the mains-synched 
clocks roll the minute digit simultaneously and all are now about 24 
seconds fast of GPS time after about two weeks. Historically here, the 
mains clocks being fast is unusual; it is more common for them to run 
slow. But, a 24 second error is not unusual.

I'm in Southern California and Walt is in Washington, also on the west 
coast but not near me. So, this mains frequency effect on old clocks is 
not local to my independent-utility city.

Please folks, stop quoting specs that may or may not still be valid and 
may or may not be complied with by electric generation utilities. 
Instead, let's get data!

I have long set all my appliance clocks to the second, even though they 
don't display seconds. The final button-push in the time-setting command 
will start the clock time at the zero second. Try it! Use a 
known-accurate (e.g. GPS) clock and set your appliance clocks, then 
check them again in a few days or more against your accurate clock. 
Report the results and your location. That's data!

I bought one of the new-Heathkit LED clock kits a few years ago; this 
new design is a mains-synched clock. I have never built that kit but I 
was disappointed to hear user complaints that it did not keep accurate 
time. In fact, though, those that were assembled may just have been 
showing the same mains-frequency issue we are discussing.

There are some cell phone apps that will read the phone's GPS and show 
time to the second. I use "Sol Et Umbra" (it's a sundial application) 
and "Atomic Time," which shows a sweeping second hand; both are free and 
Android apps.

I recommend the Geppetto GPS Clock offered on Tindie; its red LED 
display (including tenth seconds) closely resembles that of the old 
Heathkit GC-1000 clock; the latest versions access multi-GNSS signals.

Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)


On 3/25/2024 1:59 PM, Walt wrote:
> You are not alone.  I was intrigued by this thread, so I plugged in my Heathkit GC-1005 mains-powered digital clock and set the time against my PST-1030 WWV Time Clock.
> 
> I went outside to do some chores, and when I came back in 3 1/2 hours later, I'll be darned if the clock was not 3.5 seconds ahead already!  Now it's been almost 4 hours and the Heath is almost 4 seconds ahead.

...