[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.
Bruce
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