[time-nuts] Re: Can ADEV of a frequency source be correctly determined using a continuous time-stamping frequency counter?

[Bob kb8tq]

> On Nov 9, 2021, at 12:26 PM, Erik Kaashoek <erik at kaashoek.com> wrote:
> 
> As far as I understood the ADEV at a Tau of 1 second is a statement about the amount of variation to be expected over a one second interval.
> It would be nice if we would be able to measure a frequency in an infinite short interval but any frequency measurement takes time.
> What if the frequency counter does a complete measurement of a frequency source every second and all the variation within that second is hidden because of the "integration" that happens over the second?
> This is specially the case with continuous time-stamping counters.
> They can provide a precise number by applying statistical methods on many measurements done during one second but they can not provide information exactly at the end of a second.
> Is this kind of statistical measurement over a period of a second still valid for determining the ADEV at the Tau of one second of a frequency source?
> Or should there be a correction factor depending on the method used in the frequency counter?
> I tried to read some scientific studies on this subject but I am not smart enough to understand.
> Hope one of you can provide some information.
> Erik.
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