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.
