Hi
> On Dec 17, 2017, at 6:50 PM, Magnus Danielson <mag...@rubidium.dyndns.org> > wrote: > > Hi, > > On 12/17/2017 03:09 PM, Mattia Rizzi wrote: >>> you demand ergodicity, you cannot have 1/f. You can have only one or the >> other. Not both. And if you choose ergodicity, you will not faithfully >> model a clock. >> I am talking about the issues of flicker noise processes for an >> experimentalist. I know that the (current) theory is incompatible with >> ergodicy, but for an experimentalist ergodicity is an assumption that you >> have to do. You did as well, in Attila#2. > > We need to assume the properies of our model is static as we measure it and > try to estimate the model parameters. > > However, the noise we have does not have the normal convergence properties, > so much of the normal ways of defining things does not directly apply. > > Much of the methods we have come out of experimentalists trying to make > models and methods adapt to their measurement reality. > > A spectrum analyzer will pre-filter flicker noise and by that change its > statistical behavior, it will start to behave much more like white noise, but > there will be a bias in the reading. The bias in the reading depends on the > filtershape and noise type. This is known from both theory and actual > measurements. > > Similarly will counter-based observation behave. > > This heated debate on ergodic etc. needs to focus on what actually happens > and leave the theory draftingboard, since honestly, you guys to not make > enough sense even to me. Leave the fancy definitions aside for a moment and > let's focus on the properties and how we achieve them and how not to achieve > them. > >>> Please take one of the SA's you have at CERN, measure an oscillator >> for a long time and note down the center frequency with each measurement. >> I promise you, you will be astonished. >> Let's keep the focus on flicker noise, for instance, flicker noise of an >> amplifier. Noise in oscillators is more fuzzy. > > It's the noise of oscillators you need to handle, because it will be there to > act as test signals for amplifiers. > > It is however understood and we have methods to handle it. > > The models we have work within some limits. I've spent time to learn these > limits and checked it with those knowing much better. Being rigorous about > this is not for the fainthearted, and while many knows some, it does not help > if you want to be rigorous. Then again, very very few are. I have not seen > any real convergence in your debate, it's kept fluctuating without > stabilizing just as a RMS measure does on these noisetypes, you keep > deviating even wilder even. > > I find that much of the terms and definitions in classical statistics is > really not applicable as you encounter 1/f and further noises. While useful > background, as you enter the dark dungeon of time and frequency, there be > flicker dragons and other monsters that the classical statistics didn't > prepare you very well for, even if it was a good education. > > To go further, for a while all references to ergodic, I.I.D., gaussian etc. > just have to pause, because they are not contributing to understanding, they > only contribute to disagreement. Let's discuss actual properties separate, > and maybe we can come back and conclude what it means in other terms, but not > now. You then hit the very basic fact that a “standard noise process” does not cover what real oscillators or amplifiers do in the field. They have a *lot* of “noise like” issues that impact their performance. Simply coming up with a model for this or that process is only a very basic start to modeling a real device ….. Bob > > Best Regards, > Magnus > _______________________________________________ > 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.
