Hi Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For bonus points, open up the crystal package. If you have the gear to test it, take a look at what the gas *is* inside the package. ( Good luck with that :) :) :) )
If you had the gear and the willingness to scrap out OCXO’s you would find that a number of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive (thermal wise) than a *perfect* vacuum …… Bob > On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts <time-nuts@lists.febo.com> > wrote: > > I have seen that manufacturers seal their crystals in a vacuum, maybe air > interaction affects Q. The point that vacuum inhibits heat flow is something > I have never considered in ovenized units. My ovenized crystals take about an > hour to settle. I have some WW2 surplus crystals in non-sealed packages that > I have not tested... something to do.rp > > On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts > <time-nuts@lists.febo.com> wrote: > > I have been of the impression for years now that most "better" crystals are > in a vacuum. And the electrical and mechanical connections to the quartz > itself place as little mechanical load on the crystal as possible. > Thermal conductivity from the oven to the crystal itself would be both > hard to model and hard to speed up. > > IR transmission of energy to the crystal also seems problematic considering > the IR transmission of quartz and the IR reflectivity of gold > contact plating. > > Is any of this an issue? > > - Louis > > On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < > time-nuts@lists.febo.com> wrote: > >> Hi >> >>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < >> time-nuts@lists.febo.com> wrote: >>> >>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote: >>>> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < >> time-nuts@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. >>> Oh, it would be disastrous, although quartz is pretty strong, all the >> rest of the mounting components might not be. >> >> Indeed, breaking a quartz blank via thermal stress would be very hard to >> do. >> The “rest of the parts” actually are pretty durable as well. Most of it is >> metal and >> it is quite able to handle thermal issues. >> >> The big issue in a fast warm up AT turned out to be designing the heater >> and the >> mount to get the energy to the blank quickly….. If you use a small enough >> package >> and blank, the amount of power turns out to be surprisingly small. >> >> If you want to go bonkers, you mount the heaters *inside* the crystal >> package. This >> does indeed create some issues in various areas. >> >> Bob >> >>>> >>>> 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. >>> >>> Big glass mirrors for telescopes do the same. >>> >>> >>> >>>> >>>> Dave >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe send an email to time-nuts-le...@lists.febo.com >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe send an email to time-nuts-le...@lists.febo.com > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com