[time-nuts] Disciplining Rubidium
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Wed Apr 23 20:58:18 EDT 2008
SAIDJACK at aol.com wrote:
> One more comment:
>
> the GPS disciplining doesn't affect performance of parts to the 14th short
> term. GPS is used for long-term (>1000s or so) error correction, where it can
> achieve parts the 14th, but only after a day or much longer.
>
> GPS is not good enough to give you more than parts to the 8th-9th timing
> accuracy per second, which is already accuracy in the feet range. Parts to the
> 14th short term would require accuracy in the 0.00001 foot range, not possible.
>
> bye,
> Said
>
>
Said
Only true if you dont use carrier phase measurements to discipline the OCXO.
When carrier phase discipling is used then a short term (1 - 100sec)
phase error measurement noise of around 2E-11/Tau is possible.
However the accuracy at 1 day is limited to around 1E-14 by the SV local
oscillator instability and other phase delay instabilities.
Bruce
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