[time-nuts] Question about frequency counter testing

Magnus Danielson magnus at rubidium.dyndns.org
Sun May 13 14:40:52 EDT 2018


On 05/13/2018 08:09 PM, Bob kb8tq wrote:
>>> If so, that raises a whole added layer to this discussion in terms of “does it do
>>> what it says it does?”.
>> This question is also important for amateur/hobby measurement equipment. I do not need equipment that "does not do what it says it does" even if it is build for hobby use.
>> The theme about *DEV calculations has many important details I want to understand right, sorry if I asked too many questions (some of them probably were naive) and thank you for the help, it is very appreciated! I hope our discussion is useful not only for me.
> You are very much *not* the first person to run into these issues. They date back to the very early use of things like
> ADEV. The debate has been active ever since. There are a few other sub debates that also come up. The proper 
> definition of ADEV allows “drift correction” to be used. Just how you do drift correction is up to you. As with filtering, 
> drift elimination impacts the results. It also needs to be defined ( if used)., 

There is actually two uses of ADEV, one is to represent the amplitude of
the various noise types, and the other is to represent the behavior of
the frequency measure. The classical use is the former, and you do not
want to fool those estimates, but for the later pre-filtering is not
only allowed, but encouraged!


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