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

Bob Camp kb8tq at n1k.org
Fri Jan 13 14:41:37 EST 2017


Hi


That’s the way I read what they are saying. More or less: Keep the number of samples above
100, but below 300.

Bob

> On 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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