[time-nuts] GPS orthodontics: sawteeth & hanging bridges-theeffect of time averaging

Tom Van Baak tvb at leapsecond.com
Fri Dec 22 22:56:54 EST 2006

> Brooke
> I'm not convinced that one can actually directly derive the GPS timing
> receiver stability from measurements taken within a feedback loop where
> the OCXO is locked to the GPS timing receiver output. Surely one has to

Yes, I'm nervous about this approach too.

> correct for the loop transfer function. As tau approaches the loop time
> constant the accuracy of the stability measure as calculated from the
> uncorrected phase errors is degraded. Correcting for the effect of the
> loop transfer function will improve the accuracy a bit. The only way to
> measure the receiver timing stability is surely to measure it against a
> very accurate and stable standard was done when testing the M12+
> receiver at USNO.
> When the outliers are rejected these tests indicate that the sawtooth
> one day stability is around 5E-14 or so, ie somewhat better than Ulrichs
> plots show.
> Bruce

5E-14 is exactly the right number. Have a look:

A Comparison Between a 58503B and a CNS-II


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