[time-nuts] New Subscriber, DIY GPSDO project (yes, another one)
Poul-Henning Kamp
phk at phk.freebsd.dk
Tue Mar 10 23:42:03 UTC 2020
--------
In message <be8c8c2f-217b-13b8-c9ce-c4150c549852 at rubidium.se>, Magnus Danielson
writes:
>It should be said that Kalman is kind of optimum for "white" noise
>(what-ever that is), but we are far from white noise. Variants of Kalman
>filters use noise-colour compensation of some sort, and that kind of
>solves some of the issues. It does not fit the problem perfectly. This
>is why time-scale algorithms is not directly Kalman filters but only
>Kalman-esque to some degree.
And that line of thought brings us to the stochastic-ish model which
timing.com used on three 5071A and (three?) GPS's for the LORAN-C
modernization.
It's a very interesting paper and a very good idea, which works
becuase their frequency source "bottoms out" in the MVAR plot:
Frequency drift would mean you too many degrees of freedom.
The only chance I see of doing something like that, would be a Rb
where the lowest point on the MVAR plot is very close to 12h, or
even better 24h, where the GPS is similarly optimal.
Que the HP5065A...
--
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.
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