[time-nuts] accurate 60 hz reference chips/ckts

Bob kb8tq kb8tq at n1k.org
Fri Dec 15 14:00:04 EST 2017


Hi

It depends a *lot* on just where you are and how the “gird” is managed. Many years
ago, we figured out that the local power company corrected things between 4 and 5 PM.
It became a habit to fire up WWV and watch them slip seconds one way or the other. A
ten second delta was not at all unusual. ( as in 10 seconds over the hour …). Our 
guess (later confirmed) was that they ran local generation part of the day (independent 
of the grid) and then went over to interconnect. 

Bob

> On Dec 15, 2017, at 12:14 PM, Jeremy Nichols <jn6wfo at gmail.com> wrote:
> 
> I'm surprised Vlad is seeing as much as six seconds differential but maybe
> I don't understand the experiment. I've done measurements of the line
> frequency here in California and never seen much variation.
> 
> Jeremy
> 
> 
> On Fri, Dec 15, 2017 at 9:02 AM Vlad <time at patoka.org> wrote:
> 
>> 
>> 
>> I have one of my project boxes, which monitor the main freq. Here is
>> graph which reflect the time difference between of RTC (based on number
>> of pulses from OCXO) and the "MAIN TIME" which is based on number of
>> zero-cross events.
>> The observation period is 486 hours.
>> 
>> 
>> 
>> 
>> On 2017-12-14 23:13, Jim Harman wrote:
>>> On Thu, Dec 14, 2017 at 10:53 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>>> 
>>>> 
>>>> 
>>>> Of course this *assumes* an electronic approach. Given that it’s
>>>> moving
>>>> pretty slow and you
>>>> only are looking at fractions of a millisecond, one *could* do an
>>>> electro
>>>> mechanical design …...
>>>> 
>>>> Bob
>>>> 
>>>> There is interesting background on power grid frequency/time
>>>> adjustment
>>> procedures here
>>> 
>> https://en.wikipedia.org/wiki/Utility_frequency#Time_error_correction_(TEC)
>>> 
>>> and here
>>> https://en.wikipedia.org/wiki/Electric_clock#Accuracy
>> 
>> --
>> WBW,
>> 
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> 
> -- 
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