[time-nuts] Thermal effects on cables --> ADEV
Ole Petter Rønningen
opronningen at gmail.com
Fri Jan 13 12:30:37 EST 2017
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>:
> 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.
>> 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:
>> 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
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