[time-nuts] Thermal effects on cables --> ADEV

[Scott Stobbe]

I think their advice was to limit the ADEV calculation for some tau to 300
bins. The standard error on estimating the standard deviation is ~ +- 5%
for 200 samples. So loosely speaking in the neighborhood of 100-300 bins
the resulting adev will have an rms uncertainty of roughly 5%. So limiting
the number of bins to 300 for any particular tau you wish to monitor, you
will see the ADEV wonder up and down over time, but if it exceeds say 5
sigma, 25% something is up.

On Fri, Jan 13, 2017 at 12:30 PM, Ole Petter Rønningen <
opronningen at gmail.com> wrote:

> That IS interesting.. It reads to me that the advice is to keep a "moving
> 300 pt ADEV" when continously monitoring a (pair of) frequency source in
> e.g a VLBI site - the reason for limiting it to 300 pts being that much
> more than that is likely to average out potential issues..
>
> Does that make sense?
>
> > Den 13. jan. 2017 kl. 17.04 skrev Bob Camp <kb8tq at n1k.org>:
> >
> > Hi
> >
> > There’s an interesting comment buried down in that paper about limiting
> ADEV to
> > < 300 samples per point. Their objective is apparently to better
> highlight “systematic
> > errors”. I certainly agree that big datasets will swamp this sort of
> thing. I’m not quite
> > sure that I’d recommend ADEV to find these things in the first place. My
> guess is that
> > it’s the only spec they have to call the device good or bad in this case
> …They don’t seem
> > to have Hadamard in their list of variances. If I was going after
> systematics with a deviation,
> > that’s the one I’d use. Of course I probably would not use a
> something-dev in the first place.
> >
> > Bob
> >
> >
> >> On Jan 13, 2017, at 1:52 AM, Ole Petter Ronningen <
> opronningen at gmail.com> wrote:
> >>
> >> Hi, all
> >>
> >> The question of phase shifts in cables pops up every now and then on
> this
> >> list - I stumbled across a good table of measured phase shifts with
> >> temperature in different cable types in this paper:
> >> http://www.ira.inaf.it/eratec/gothenburg/presentations/ERATEC_2014_
> PresentationWSchaefer.pdf
> >> that I though would be of interest to others.
> >>
> >> A quick summary given below, see pdf for full details. Lots of other
> >> interesting stuff in there also.
> >>
> >> Values in ppm/K, for 10 Mhz except when otherwise stated. (The paper
> gives
> >> values for 5, 10 and 100Mhz)
> >>
> >> Huber-Suhner Multiflex 141: -6
> >> RG-223: -131.9
> >> Semiflex Cable: -11.5
> >> Huber-Suhner: -8.6
> >> Times Microwave LMR-240: -3.4
> >> Times Microwave SFT-205: 7.7
> >> Meggitt 2T693 SiO2: 30.6
> >> Andrew FSJ-1 (@5Mhz): 25
> >> Andrew FSJ-4 (@5Mhz): 10
> >> Andrew LDF-1P-50-42: 2.8
> >> Andrew LDF4-50A: 4.7
> >> Times Microwave TF4FLEX (@100Mhz):6.4
> >> Phasetrack PT210 (@100Mhz): 2
> >>
> >> Ole
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