[time-nuts] GPSDO control loops and correcting quantizationerror

[Poul-Henning Kamp]

In message <BAY162-W9FFF4214C4DE8FD1752F3DF960 at phx.gbl>, Tom Knox writes:

>Great dialog, One thing I have seen is the Allan intercept almost
>always has a "knee". If you wanted the best possible GPS quartz
>reference developing a variable Allan intercept would allow this
>knee to be moved and then mathematically removed during a gated
>measurement.
>Allowing to effectively see behind he knee offering lower uncertainty
>in this important area.

I did try a spectral approach before I settled on the current approach,
because I foresaw the precence of 12 and 24 hour periodicities, but
while good on the paper and post-factum, I never managed to get it to
autoestimate reliably in real-time.

If you can find the paper about the algorithm timing.com was founded
on, you will find much interesting fodder therein, but my
reimplementation of their algorithem only worked for Rb's I could
never get it to do anything usable for OCXOs.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.