[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

[Bob kb8tq]

Hi

Well …. folks have made AT based OCXO’s that heat up in “seconds” ( as in under
a minute ). Back in the 1980’s they stabilized to < 1x10^-7 at least as fast as the 
then typical SC based OCXO’s did ….  ( < 6 minutes ). Collins bought quite a few of 
them over the years. 

Bob

> On Jun 10, 2022, at 1:25 PM, Dr. David Kirkby via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts <
> time-nuts at lists.febo.com> wrote:
> 
>> 
>> On the subject of rapid warm up. I suppose if you had a need, one could
>> dump as much power as you need into the heater. Turn on oscillator,
>> lights in room dim for a few moments.
>> 
> 
> Is that not likely to damage a crystal? Different parts of the crystal and
> likely to be at significantly different temperatures at the same time,
> putting a lot of stress on the crystal due to a thermal gradient. It's
> probably a bit academic, as nobody is going to make an oven that heats up
> in fractions of a second, but if one did, I suspect it might not do the
> crystal a lot of good. This is only an educated guess - I don't have
> anything to back it up.
> 
> At the other extreme,  would there be any advantage in actually heating the
> crystal very slowly, over the course of an hour/day/week, so the
> temperature gradient across the crystal is very small? Of course, if an
> oven took ages to reach the correct temperature, it would be inconvenient
> for most applications, but for some applications, the advantages might
> outweigh the disadvantages. Of course, if one does this, I suspect one
> would have to cool the crystal slowly too to prevent a significant thermal
> gradient across the crystal.
> 
> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I
> was told that Nikon cools the front element over a period of 6 months to
> reduce stresses in the glass.
> 
> Dave
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