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

[Bob kb8tq]

Hi

The simple answer is that there are no shortcuts allowed if you are after a proper
ADEV. You take the (single) phase samples at the specified tau and push them into
the math. Anything else you do, will reduce the noise and thus compromise the noise 
measuring properties of the approach. 

Bob

> 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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