[time-nuts] WTB: GPSDO

Attila Kinali attila at kinali.ch
Wed Mar 15 04:09:09 EDT 2017

On Tue, 14 Mar 2017 21:25:19 -0700
Chris Albertson <albertson.chris at gmail.com> wrote:

> You can also verify the GPSDO is working correctly by looking at the
> EFC voltage.  That is the control signal the controller sends to that
> $25 eBay crystal.  You'd expect that the ESFC volts follows some kind
> of theory and tracks the environment and you'd not expect a random

This depends very much on the oscillator used. If it's a good OCXO,
you will see hardly any influence from environment and the EFC will
be dominated by GPS noise at short time scales and aging of the OCXO
at long time scales. Have a look at what TvB reported in November[1,2]
on the measurement of a bunch of Thunderbolts(free running). Yes, there
is something that seems to be environmental effects for some oscillators
at some time scales. Figuring out where you actually see such effects
will need some serious statistical skills. IMHO it's much easier to just
get a known-good GPSDO and a rubidium for verification.

			Attila Kinali

[1] https://www.febo.com/pipermail/time-nuts/2016-November/101913.html
[2] https://www.febo.com/pipermail/time-nuts/2016-November/101939.html

You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor

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