[time-nuts] DC Voltage Ramp?

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Sep 4 14:29:47 EDT 2005

In message <431B3C6A.9000808 at pacific.net>, Brooke Clarke writes:

>BUT, if instead of using a fixed control voltage, a Ramp is used then 
>this will not happen.  Now instead of using GPS to control a fixed 
>voltage it's used to control the slope of the ramp.
>What am I missing?

I've played with a PLL which estimates not only frequency error but
also frequency drift, and have found that it is very very tricky to
get a consistent result with averaging times less than days.

The driftrate of a good OCXO is below a lot of noise factors so
I have only been able to estimate it reliably on weekly timescale.

The next thing is that once you do that, you realize that the
noise in the frequency estimate makes it almost totally pointless
to apply the drift correction unless you anticipate very long
synchronization outages.

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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