Hi An SC cut OCXO stabilizes a bit faster from the temperature steps. The procedure Rick described is indeed the right way to do it for an SC. It takes less time and is reasonably accurate. For a super duper job you might come back a day later, but the pot its self (backlash etc) will probably limit you. With another parameter to read out (pot voltage maybe) as you do the set, things could get more precise.
AT’s and BT’s are not quite as forgiving as an SC. The process I outlined is a bit of an exaggeration, but it gives you a good idea of what you are in for. Doubly so if this is your first attempt to do a blind hole adjust on a pot to 1/32 turn ….(engage without moving it, back off for the backlash, return, past previous point, stop at 1/32 .. so much fun). Bob > On Feb 28, 2016, at 11:19 PM, Glenn Little WB4UIV > <glennmaill...@bellsouth.net> wrote: > > While in the navy, I had to repair a hp cesium standard. > The control circuit had the oscillator slewed to one limit, I do not remember > whether high or low. > We had no spare parts to support this standard. > The only option was to run the standard open loop. > Over a period of two hours, I had the standard off for no more than 15 > minutes total. > To get the standard back on frequency, I had to compare this standard to the > other standard using an oscilloscope to produce a Lissajous pattern. > I set the oscillator on frequency by stopping the rotation. > I checked it again in 6 hours and the pattern was fastly rotating. > I reset the frequency and checked it at 6 hour intervals. > It took two weeks for the oscillator to thermally stabilize after being off > only 15 minutes. > Be prepared to have to wait to get the oscillator thermally stabilized. > > I am not positive that this was a 10544A, but, it was a similar ovenized > precision oscillator. > > > YMMV > > 73 > Glenn > WB4UIV > > > On 2/28/2016 8:10 PM, Bob Camp wrote: >> Hi >> >> Except …. >> >> The big steps give you more “thermal shock” on a BT and that slows things >> down. >> >> Bob >> >>> On Feb 28, 2016, at 7:28 PM, Richard (Rick) Karlquist >>> <rich...@karlquist.com> wrote: >>> >>> >>> >>> On 2/28/2016 7:01 AM, Bob Camp wrote: >>>> Hi >>>> >>>> It’s not an electrical issue as much as a heat issue …. >>>> >>>> Before you start, consider that you will be doing something like: >>>> >>>> Move trimmer 1 turn CW >>>> Wait 10 minutes >>>> read frequency >>>> Move trimmer 1 turn CW >>>> wait / read >>>> Move trimer 1/2 turn CCW >>>> wait / read >>>> Move trimmer 1/4 turn CW >>>> wait / read >>>> Move trimmer 1/8 turn CCW >>>> wait / read >>>> Move trimmer 1/16 turn CW >>>> wait / read >>>> Move trimmer 1/32 turn CW >>>> wait / read >>>> >>>> That is indeed an ideal version. You likely will do multiple steps at each >>>> of the stages rather >>>> than get it right the first time. The part needs to be warmed up for a few >>>> days before you >>>> can get to the 1/32 turn level. You also need a good standard to compare >>>> to. >>>> >>>> Bob >>>> >>> >>> Instead of that, start with the pot at max temp, and have the counter make >>> measurements at, say, 1 second intervals as the oven warms up. >>> You can tell by looking at the plot what the peak frequency is. Now >>> that you know the peak frequency you are shooting for, it will take >>> a lot less trial and error to find the oven setting that produces it. >>> >>> Rick >>> _______________________________________________ >>> 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. >> > > -- > ----------------------------------------------------------------------- > Glenn Little ARRL Technical Specialist QCWA LM 28417 > Amateur Callsign: WB4UIV wb4...@arrl.net AMSAT LM 2178 > QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR > "It is not the class of license that the Amateur holds but the class > of the Amateur that holds the license" > --------------------------------------------------------------------------- > _______________________________________________ > 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.