Bert, When you do tests like this, how long do you let the oscillators "settle" prior to testing?
Doc Sent from my iPad On Sep 30, 2012, at 4:23 PM, ewkeh...@aol.com wrote: > Rick > I have some 10811's all below 1 E-12 in the 1 to 100 sec. range, a few as > low as 4 E-13 at 10 seconds. How low have you seen, I have the opportunity > to test 40+ units and hope to find a few even better ones. Any guidance will > be appreciated. > My best reference is 3 E-13 so any thing as good or better would have to be > tested by some one else after initial test. > Bert Kehren > . > > > In a message dated 9/30/2012 3:49:33 P.M. Eastern Daylight Time, > rich...@karlquist.com writes: > > I only measured one 10811. However, John Vig's tutorial > (available at IEEE UFFC) rather categorically states that > piezoelectric resonators have flicker noise of frequency. > What I measured was most closely related to phase noise, > as opposed to Allan Deviation. Phase noise of 10811's is > more consistent unit to unit than ADEV and certain more consistent > than aging. BTW, ADEV at HP was measured against a > special 10811 that was 500 Hz off frequency. I was never > able to find out how they arrived at this "golden" unit. > But it seems clear that it could not have been the > best ever unit for ADEV, thus the real "golden" units > that came down the pike were simply rated as ADEV too good > to measure. I tried to get a project started where we > would use a frequency synthesizer to do the offset. > Then we could take the best units and compared them against > each other. Then, as well accumulated test data, the > cream would gradually rise to the top and we would have > some true golden units. The problem was that there ADEV > at those levels wasn't a "money spec". > > Rick > > On 9/30/2012 12:16 PM, Ed Palmer wrote: >> Would this characteristic be similar across all 10811s or would there be >> as much unit to unit variation as there is for aging and Allan Deviation? >> >> Ed >> >> On 9/30/2012 11:03 AM, Richard (Rick) Karlquist wrote: >>> I recently modified an old 10811 to bring out the crystal >>> leads on miniature coax (instead of having them connect >>> to the oscillator circuit). This allowed me to measure >>> the crystal's inherent flicker noise of frequency. >>> The measurements indicate that the 10811 phase noise out >>> to at least 100 Hz is entirely due to the crystal. >>> An interesting aspect of flicker noise of frequency >>> is that Allan deviation is independent of tau. Thus, >>> just one number describes the crystal noise. >>> >>> Rick >>> >>> On 9/30/2012 4:44 AM, Bob Camp wrote: >>>> Hi >>>> >>>> Close in, it looks like it's pretty much the crystal and the loading >>>> of the bridge oscillator. >>>> >>>> Bob >>>> >>>> On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist >>>> <rich...@karlquist.com> wrote: >>>> >>>>> The E1938A uses a crystal that is basically the same as >>>>> the 10811 crystal except that it is in a reduced height >>>>> package. However the phase noise is not as good as a >>>>> 10811 due to broadband noise in the automatic frequency >>>>> control circuit. By the time I discovered this, it >>>>> was too late to try to fix it. >>>>> >>>>> Rick Karlquist N6RK >>>>> E1938A designer >> >> >> _______________________________________________ >> 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.