Yes, I did, because nobody else had, and I was curious. We were seeing changes along the lines of parts in 10^8, about an order of magnitude worse than tempco. This was for something like dry nitrogen purge all night vs 50 degrees C, 90% humidity for an hour or two.
After these horrible tests, I decided that the E1938 would definitely be hermetic. Rick N6RK [EMAIL PROTECTED] wrote: > Rick- > > You've peaked my interest. Has anyone ever collected any > data on 10811 frequency vs. humidity or dew point? > > -Brian, WA1ZMS > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Behalf Of Richard (Rick) Karlquist > Sent: Tuesday, June 20, 2006 1:03 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] 10811 Extra Lagging etc > > >> Given that HP's engineers have done such a good job with >> the oven and oscillator design, is there anything to be gained >> by adding extra thermal insulation (lagging)? How much > > Not a good idea. The best thing you could do to improve > temp stability of a 10811 is to tweak the resistors that > proportion the power between the two heater transistors. > At some ratio, the thermal gain will peak at over 1000 > typically. If you just take pot luck, you would be lucky > to do 100. You are still limited by the tempco of the > electronics, no matter what thermal gain you achieve at > the crystal. > > You should also be aware that the 10811 is fairly humidity > sensitive, which can seem like temperature sensitivity > if the humidity and temperature change together. > > The HP E1938 was a much better design in terms of environmental > insensitivity, but that didn't help much because the > ultimate stability was limited by crystal frequency jumps, > which didn't seem so bad with the 10811 due to the large > environment errors in it. In the E1938 they stuck out like > a sore thumb. > > Rick Karlquist N6RK > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
