[time-nuts] Re: pulling some crystals

[Jim Lux]

 
I can't remember where this thread started, but do you actually need to move the oscillator at all? Or is "knowledge" good enough?
For instance, could you have a (high quality) DDS to generate a desired frequency, and the commanding of the DDS is done by comparing your oscillator and the 1pps from external reference.

This may or may not work, depending on your phase noise requirements.  There are techniques for DDSes to make the close in phase noise small (at the expense of raising it farther out - it's always like squishing a balloon).

Or some other technique of taking a quiet, but movable, oscillator and locking it to your "good" oscillator (and using GPS to set the relative frequencies).


On Tue, 12 Dec 2023 17:20:21 +1100, glen english LIST via time-nuts <time-nuts at lists.febo.com> wrote:

Well today Bob, I find hysteresis, retrace, and spurious modes all
affected by pulling the temperature all over the place ( as an attempt
to get another handle of control) .  Ands different starting behaviour
at temperature spots. golly.

Propensity of spurious modes (my 3OT xtals) seems to be dependent on
temperature, also. golly.

This is tough. Might just have  tweak  in there that gets adjusted every
few years.

Holding it over a narrow temperature range (without the intention of
stability) appears to improve behaviour of hysteresis, retrace and
spurious modes, at least over a few hours.

IE by holding it in a in a small temperature range, I reduce the number
of things that can affect the outcome.

Time to go back and read some more Rubiola.

Bob, I built your low noise oscillator for a fundamental AT xtal.
Reduced bad behaviour, but more noise than the overtone crystal.

Geeez who would build crystal oscillators for a living ????

glen

On 12/12/2023 11:00 am, Bob kb8tq wrote:
> Hi
>
> When you change the oven temperature you get both first and second
> order temperature effects. You also impact the degree aging has
> “settled out”.
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