[time-nuts] Re: 10811A settling time

[Attila Kinali]

Moin,

On Sun, 31 Mar 2024 14:47:33 -0400
Bob Camp via time-nuts <time-nuts at lists.febo.com> wrote:

> Your OCXO (pretty much any OCXO) goes from room to “pretty hot” ( that might be 20C up to 90C) 
> in a short period of time. The temperature coefficients of expansion of the various elements of the 
> crystal never match up perfectly. The same is true for the “stuff” in most of the other components. 
> This stress translates to a change in value for the components and a change in frequency for the crystal. 

To add to Bob's explanation: This also goes for the oven being constantly on
and just the oscillator being power cycled. While the crystal's temperature
does not change (much), it is still a mechanical device that went from being
in storage (albeit hot), to moving. I.e. a lot of equlibrium points just
shifted and need time to relax again. Thus, if you want an OCXO to be
ready to use, while not powering the whole instrument, you still have to
power its oscillator as well.


> > On Mar 31, 2024, at 10:59 AM, alan bain via time-nuts <time-nuts at lists.febo.com> wrote:

> > The manual for the 10811A suggests running for 10days before checking
> > drift, but to do so requires a Caesium frequency reference which -
> > alas - I lack!

You don't need a caesium standard to check for drift of an OCXO.
A simple GPSDO will do. All you have to do is measure over several
hours, maybe a day and average the data. If you have a means to measure
the phase (e.g. use the PPS of GPS to start the measurement and the 10MHz
output of the OCXO to stop it), then you are limited by the noise of the
GPSDO only, which averages out pretty quickly and you'll be limited by
the OCXO's instability for anything longer than 1k-10k seconds.


			Attila Kinali
-- 
Science is made up of so many things that appear obvious 
after they are explained. -- Pardot Kynes