[time-nuts] 4046 experiment for gpsdo

Bob Camp kb8tq at n1k.org
Sat Sep 26 20:04:14 EDT 2015


Hi

If you digitize the beat note it’s fairly simple:

The beat note is not really a sine wave. It’s periodic, but not a pure sine. The 
reason is fairly simple. The frequency changes as the beat note changes the EFC.
You have a lower frequency as it gets closer to the “zero frequency”. 

The net result is a signal that is a bit flat on the side that is towards the zero. It’s a 
bit sharper away from the zero. Fit it with a sine wave and you will get a residual. From that
you can work out which side is which.

Bob

> On Sep 26, 2015, at 5:47 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> magnus at rubidium.dyndns.org said:
>> Another method would be to measure the phase-detector beat-note  frequency
>> (most have mixer-like behavior), which you should be able to  measure with
>> quite good precision, then set the EFC accordingly and then  close the loop.
> 
> How do you get the sign out of a beat note?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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