[time-nuts] Can anyone help?

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Oct 28 18:15:27 EDT 2006

ABSA Email wrote:
> Hi there,
> I need some advice.
> I'm not into the nano-second accuracy region, so this could well be
> considered OT.
> 1. I have a Gent's mechanical clock, and I check it by my computer clock. To
> set the computer clock, I use the built-in synchronisation to
> time.windows.com, or time.nist.gov.  How accurate can this be by the time
> that the synchronising signal reaches my computer in South Africa?  Are
> there any time stations nearer to me than USA? Does the time signal update
> itself as it travels the Internet to me?
> 2. This is for frequency measurement. Can anyone recommend a divide-by-ten
> counter to use as a pre-scaler up to 500 MHZ?
> Paul Galpin
> South Africa
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Try an MC12080 programmable prescaler from ON semiconductor.
This device can be configured to divide by 10, 20, 40, or 80 as set by 
pin connections.

Its maximum input frequency is 1100 MHz.
However its not very useful below 100MHz.

What is the minimum input frequency for the prescaler?
If you want it to operate down to dc then you may have to use an ECL 
universal counter set to divide by 5 followed by an ECL divide by 2 
The output flipflop being used to produce a 50% duty cycle output.


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