[time-nuts] Comparing Reference Accuracy

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu May 22 17:45:39 EDT 2008

Stanley Reynolds wrote:
> Reduced VE2ZAZ controller to be used as a counter.
>       http://i307.photobucket.com/albums/nn306/stanleyreynolds/VE2ZAZreduced.jpg
Resolution is still inadequate for meaningful comparisons with short 
averaging times.
For longer averaging times all GPSDOs will achieve the stability of the 
GPS reference.
For intermediate averaging times the effect of the disciplining loop on 
the oscillator instability has to be taken into account.

You need to use a scheme that is capable of picosecond or subpicosecond 
resolution for single shot measurements if you want to make meaningful 
measurements of ADEV for short averaging times.
You also need to reduce the measurement bandwidth or wideband phase 
noise may constitute a lower  limit the measurement noise.

With oscillators that dont have state of the art stability lower phase 
measurement resolution may suffice.


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