Hi What level of stability are you trying to measure?
What sort of offset frequency are you running? What kind (phase noise / spurs / adev) offset oscillator are you using? What sort of limiter are you running with what sort of pre filtering? We have run around on a lot of generalities. You may have some issues that are specific to your setup. There is no “one size fits all” approach here. If you are running a couple of oscillators it the THz region and trying to look at ADEV from 1us to two months tau with one setup, a lot of what we have been saying simply does not apply. Bob > On Jan 21, 2018, at 4:23 AM, [email protected] wrote: > > > Corby, > thanks for the information. > > I'm definitely interested in the short therm ADEV but especially for Tau > from 1 day and over to test high stability standard over the time. > I will have further tests. > Cheers, > Luciano > > > Da "time-nuts" [email protected] > A [email protected] > Cc > Data Sat, 20 Jan 2018 16:14:10 -0800 > Oggetto [time-nuts] Time interval measurement vs dual mixer method > Luciano, > > I don't know of a commercial version. > > As you have seen as the two signals move away from close phase > coincidence the system noise level will increase. > > This is because the common offset oscillator noise will only cancel when > the phases are closely matching. > > This is mainly important for the lower Tau (like 1 to 10 seconds). > > I will normally adjust the phase of my reference or DUT so that myTIC is > reading 0.00000XX (close to phase match) and very slowly rising. (with my > setup most DUT will age downward). > > Then I start logging the data. > > A typical run with a 1 week aged quartz will show the TIC count slowly > increase (and may wrap) and then as the aging continues the count will > reverse and eventually go "below" zero and wrap. > > A phase plot will show a nice parabolic looking curve going up and then > as the aging crosses it will curve down. > > If there are wraps the plotter program can take them out. > > Any long plot of Quartz WILL wrap! > > Now if you plot the AD you will see a normal type plot for a good Quartz. > > If the TIC count increased well past coincidence only the Higher Taus > will be accurate. > > For the lower Tau you need to cut off the data past where it climbed too > high. > > I typically will setup as described and run a short log of say 5 minutes. > > I might only keep the first 100 Seconds and plot the AD against that. > > This will give you an accurate plot for the lower Tau. > > These two plots can then be combined to give you the whole range. > > The attached plot of an FE405B illustrates this. > > The Red plot is against a very good FTS 1200 (2X10-13th at 1 thru just > past 10 Sec) > > The blue continuation is against a very good HP 5065A (1.5X10-13th at 100 > Sec) > > So if the lower Tau are important only use logged data that are in near > phase match! > > Hope this helps! > > Cheers, > > Corby > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
