[time-nuts] Best GPS 1PPS Accuracy

Tom Van Baak tvb at leapsecond.com
Thu Dec 14 14:55:44 EST 2006


> Hello Said,
>
> from my own experience in detecting and removal of outliers i can asure
> you that it is a challenging and ambitious task in statistical math. I
> fear you expect too much from a receiver's TRAIM firmware to compute the
> necessary statistic math on a pulse to pulse base. Nevertheless you can
> do it on your own if the microcontroller that compares the LO to the
> GPS's 1pps has enough RAM and processing power. 

I second Ulrich's comments. A certain amount of
sanity checking on your end is worthwhile. You can
get GPS 1PPS glitches, OCXO glitches, and TIC
glitches. No need to decide which is which; just do
outlier detection and you solve them all.

The beauty of a GPSDO is that you're only changing
the DAC every few minutes so there's plenty of time
to look carefully at the quality of your 1 Hz samples
before you commit the DAC update.

It would be a more difficult problem if you needed to
update the DAC in realtime.

/tvb





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