[time-nuts] Question about noisetypes and ADEV

Tom Van Baak tvb at LeapSecond.com
Fri Oct 26 14:27:43 EDT 2018


> In case the screenshot does not make it though;
> W PM starts at 1.69e-9

For this you should expect 1.73 which is sqrt(3). For example:

C:\tvb> rand1 1000000 | adev4 /a 1
rand1 1000000(count) 1(sdev) 0(mean) 1540577979(seed)
** tau from 1 to 1 step 1
       1 a 1.732671e+000 999998

> W FM starts at 9.74e-10
> RW FM starts at 6.92e-10

Not sure about those two. Magnus might know.

There could also be subtle issues with your RNG or your algorithms. To double check your work, use the noise gen feature of Stable32. It's very nice. All 5 noise types and more. Consider also using a million points and then clip the last decade or two of the ADEV plot. That helps with the unnatural wiggles on the right. You will always find run to run variation. This is ok. Random is not always textbook random.

See also: http://leapsecond.com/pages/allan/Exploring_Allan_Deviation_v2.pdf

Raw data: http://leapsecond.com/pages/allan/

/tvb




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