Hi!
From: "Bob kb8tq" <kb...@n1k.org>
There is still the problem that the first post on the graph is different
depending
on the technique.
The leftmost tau values are skipped and they "stay" inside the counter. If I
setup counter to generate lets say 1s stamps (ADEV starts at 1s) it will
generate internally 1/8sec averaged measurements, but export combined data
for 1s stamps. The result will be strictly speaking different, but the
difference should be insignificant.
The other side of all this is that ADEV is really not a very good way to
test a counter.
Counter testing was not a main reason to dig into statistics details last
days. Initially I used ADEV when tried to test the idea of making the
counter with very simple HW and good resolution (BTW, it appeared later it
was not ADEV in reality :). Then I saw it worked, so I decided to make a
"normal" useful counter (I liked the HW/SW concept). The HW has enough power
to compute various statistics onboard in real time, and while it is not
requisite feature of the project now, I think it will be good if the counter
will be able to do it (or at least if it will export data suitable to do it
in post process). The rest of the story you know :)
If you are trying specifically just to measure ADEV, then there are a lot
of ways to do that by it’s self.
Yes, but if it can be done with only some additional code - why not to have
such ability? Even if it has some known limitations it is still a useful
addition. Of cause it should be done as good as it can be with the HW
limitations. Also it was/is a good educational moment.
Now it is period of tests/experiments to see the used technology
features/limitations(of cause if those experiments can be done with the
current "ugly style HW"). I have already got a lot of useful information, it
should help me in the following HW/FW development. The next steps are analog
front end and GPS frequency correction (I should get the GPS module next
week). I have already tested the 6GHz prescaler and now wait for some parts
to finish it. Hope this project will have the "happy end" :).
All the best!
Oleg
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