Hi Tossing a nice fluffy towel over it works pretty well. Just the thing if you are doing a bench turn hunt on an AT based OCXO. It's also a quick way to answer the age old question "is it broke or is it just all the people walking by while I'm trying to test it".
You need something that will let you go say 25C 5C 25C 45C 25C. Each time you make a change and re-test, you want to run the same temperatures. You need enough air circulation (and proper ducting) so that the device OCXO stabilizes quickly. 300 to 600 CFM is the range most chambers run in. Dead air = hard to know what temperature you are at / large delta T within the chamber. A dwell of maybe an hour at each one is about right. A Tenny Jr is a pretty good chamber for home use (no CO2). Keeping the refrigeration repaired can be a chore though… Bob On Jul 26, 2013, at 3:33 PM, paul swed <paulsw...@gmail.com> wrote: > So laying a sock over the insulated oven can doesn't count? Its a thick > sock. > Still not at the stage of needing a chamber I am 45 Hz off. > > > On Fri, Jul 26, 2013 at 2:36 PM, Bob Camp <li...@rtty.us> wrote: > >> Hi >> >> Doing any real adjustment on these OCXO's pretty much requires you have a >> temperature chamber and a pretty good standard. A GPSDO will do for the >> standard, the chamber is a bit harder to come by. >> >> Bob >> >> >> On Jul 26, 2013, at 1:38 PM, Rick Karlquist <rich...@karlquist.com> wrote: >> >>> Ed Palmer wrote: >>>> Hi Paul, >>>> >>>> Did you see this page that talks about tweaking the 10811 oven >> controller? >>>> >>>> http://www.realhamradio.com/z3801a-turning-point.htm >>>> >>>> Ed >>>> >>> >>> Although this article anecdotally claims success, it overlooks >>> a number of important issues. First of all, a large proportion >>> of 10811 crystals DO NOT HAVE A TURNOVER. They merely have a >>> very low TC around 82 degrees. It is ALWAYS 82 degrees for these >>> crystals. The crystals that do, technically, have a turnover, >>> still have very low TC even if the oven is slightly off the turnover. >>> Secondly, the tempco of the electronics, specifically >>> the selected 2N5179 oscillator transistor, is a significant player. >>> The thermal gain, if properly adjusted, is around 1000 at the >>> crystal, but is much less at the oscillator transistor. It may >>> very well be the dominant factor in overall oscillator tempco. >>> Possibly, if you have a crystal with a turnover, you should >>> deliberately operate off the turnover at a point where the crystal >>> drift cancels the drift of the electronics. >>> If you want to tweak a 10811, you should also tweak the thermal >>> gain by custom adjustment of the heat balancing resistors for >>> the heater transistors. This has to be done by converting the >>> oscillator to mode B and then converting it back to mode C >>> afterwards. >>> >>> Rick Karlquist N6RK >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
