[time-nuts] Re: 3-Cornered Hat fails with negative variances, is there anything I can to to improve?

[Erik Kaashoek]

Jim
I'm not able to access the paper as I'm not an IEEE member.
And the math probably will be way over my head anyway.
Do I understand correctly that for testing one should next to something
like the ADEV of the counter noise, also measure the histogram to check if
the noise is gaussian and the PSD to check for hidden frequencies in the
noise?

If the three phase relations are measured simultaneously and the 3
equations solved to calculate A, B and C. Would calculating the ADEV of A,B
and C not eliminate the noise of the measurement device?
Keep in mind it's been a very long time since I studied statistics.
Erik

On Sun, Oct 16, 2022, 20:30 AC0XU (Jim) via time-nuts <
time-nuts at lists.febo.com> wrote:

> I published a couple of papers on Tri-Cornered Hat and Grosslambert.
>
> https://ieeexplore.ieee.org/document/9234829
>
> https://www.ion.org/publications/abstract.cfm?articleID=17805
>
> My position is that this is a statistical problem, and it is best to
> analyze the results statistically. In particular, you can estimate the
> distributions of the measurements and the computed ADEV estimates. You
> never end up with unphysical results because even if the simple
> tri-cornered hat formula produces a negative result for some time scale,
> the estimate includes an uncertainty interval that includes positive
> values. Unfortunately, the usual ADEV apps don't perform this analysis.
> Some day I hope to publish one but that hasn't happened yet. The algorithm
> I use is described in the first paper.
>
> Sadly, no manufacturer of stable timing devices makes much of an effort to
> capture the statistical properties of their devices. The most that most
> manufacturers do is post ADEV values at a few time scales. I haven't seen
> any datasheets with confidence intervals for ADEV. Also, manufacturers can
> be cavalier with temperature sensitivity, which can be huge even for OCXOs
> and  "atomic clock on a chip" devices. So you have the right idea - testing
> is super important.
>
>
>
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