Hi Frequency is a "change over time". If delta time is zero it is undefined. As you observe it in shorter time periods, the accuracy / stability gets worse. Since the error bars expand there isn't much of a limit as you go shorter. They are not quite the same thing, but they are related.
Bob > On Sep 1, 2016, at 6:35 PM, Nick Sayer via time-nuts <time-nuts@febo.com> > wrote: > > Just a stupid question... > > On a theoretical basis, can one speak of the limit of the frequency observed > as tau approaches zero? > > Might that in some way be the "instantaneous frequency" which people often > think of? > > I rather suspect the answer is "no," but I'll ask anyway. > > Sent from my iPhone > >> On Sep 1, 2016, at 3:26 PM, Charles Steinmetz <csteinm...@yandex.com> wrote: >> >> Bert wrote: >> >>> maybe some one smarter than us can working with the parameters that Tbolt >>> makes available better performance can be achieved >> >> I am quite sure of that >> >>> the frequency is being changed to compensate for time >> >> Yes, the PPS is steered by making slight adjustments to the OCXO frequency. >> But you can make these adjustments as arbitrarily small as you want with the >> setup parameters. I run my Tbolts with pretty tight limits on the frequency >> adjustments. >> >>> and we do not care about ADEV, we care about the actual >>> frequency at that moment it goes in to the measuring device >> >> There is no "there" there. One never makes a frequency measurement at just >> one instant -- the measurement will ALWAYS be done over a macro time >> interval (very often, one second, sometimes 0.1, 10, 100, or 1000 seconds). >> We never observe, and have no way to know, the instantaneous frequency (as >> you put it, "the actual frequency at that moment it goes into the measuring >> device") -- so how can we care about it? The only thing relevant (or even >> meaningful) is the average frequency during our measurement interval. >> >> xDEV tells us half of what we want to know -- how stable our oscillator is >> from one measurement interval to another. We would also like to know what >> frequency it is wobbling around -- the "centroid" frequency, if you will (to >> borrow a geometric term). (Mathematicians can argue for days about which >> type of "average" is appropriate here -- the rest of us just pick one and >> carry on.) ADEV does not tell us this "centroid" frequency directly, but it >> can be extracted from the same measurements we took to calculate ADEV. >> >> I think you are being misled by a belief that the linguistic construct, >> "instantaneous frequency," has real meaning in the world. It doesn't. >> >> Best regards, >> >> Charles >> >> >> _______________________________________________ >> 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.
