Tom Clark, K3IO said the following on 12/24/2006 12:26 AM: > The straight ADEV will certainly be affected if there is a drift. The > ADEV for delta time=T is simply the RMS difference between the clock > phase at time t and time t+T. Any rate offset will appear in this > calculation.
I must have been mistaken then, because I recalled (probably incorrectly) some conversation here that a linear drift would not have a significant impact on the calcluation. > If you are using STABLE32, you might want to fit out a smooth > polynomial with the tools that are supplied. Or as an alternative, use > the Modified ADEV; this computes the difference to both earlier and > later times and implicitly includes the removal of a simple offset. I will play a bit more with the different versions of ADEV. > John -- you can get info on STABLE32 at [1]http://www.wriley.com/. > Even if you don't get the software, the manual is a good bible and can > be fetched at [2]http://www.wriley.com/Manual146.pdf. Pay special > attention in the manual to pages 31-49 for a discussion of the types > of variances that are of use in the community. FYI -- The folks who > maintain the Rb and Cs clocks on the GPS satellites are sold on the > Hadamard variance as a long-term performance measure. > To learn how to read an interpret the slopes on an ADEV plot, refer to > pages 77-83. On page 79, you will see that the Modified ADEV gives you > more information in the short-term (i.e. the area where the VCXO is > the principal contributor) part of the curve for White vs Flicker > phase modulation. > I highly recommend STABLE32 -- many of us have found it well worth the > $400 price that Bill Riley charges for his labor of love! > 73, Tom Yeah, Stable32 really is excellent, and the manual has lots of good stuff that I need to study more! Thanks! 73, John _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
