Re: [time-nuts] Thermal effects on cables

of precise time and frequency measurement Subject: Re: [time-nuts] Thermal effects on cables On Mon, 23 Jan 2017 15:13:39 + REEVES Paul <paul.ree...@uk.thalesgroup.com> wrote: > Surely the impedance of the cable is only affected by the ratio of the > inner conductor and out

Re: [time-nuts] Thermal effects on cables

On 23 January 2017 at 17:29, Tim Shoppa wrote: > > Funny how people always want to put the words "dielectric" and "constant" > right next to each other but we know it isn't constant :-) > > Tim N3QE > Yes. I will have to look into this, as I see some quite widely different

Re: [time-nuts] Thermal effects on cables

oI On 23 Jan 2017 17:02, "REEVES Paul" wrote: > > Hi David, Hi Paul > Surely the impedance of the cable is only affected by the ratio of the inner conductor and outer conductor diameters modified by the internal dielectric constant, nothing to do with the

Re: [time-nuts] Thermal effects on cables

A google search for digiwave turned up cheap coax at walmart. I don't know how well copper clad steel holds up in the kHz, low MHz. On Mon, Jan 23, 2017 at 5:01 PM, Bob Camp wrote: > Hi > > Back a long time ago the people I was working with spent time looking > at the impedance

Re: [time-nuts] Thermal effects on cables

Hi Back a long time ago the people I was working with spent time looking at the impedance of a variety of coax cables. The data they came up with on some varieties of cable would suggest that cable is not an outlier… Bob > On Jan 23, 2017, at 3:08 PM, jimlux wrote: > >

Re: [time-nuts] Thermal effects on cables

On 1/23/17 9:16 AM, Bob Camp wrote: Hi Nothing is ever simple if you dig deep enough: http://www.jensign.com/RG58U/ http://www.cliftonlaboratories.com/the_curious_case_of.htm here's my guess on the curious case cable: it was mismarked by accident at the factory (e.g. 93 ohm coax, marked

Re: [time-nuts] Thermal effects on cables

On 1/23/17 7:13 AM, REEVES Paul wrote: Hi David, Surely the impedance of the cable is only affected by the ratio of the inner conductor and outer conductor diameters modified by the internal dielectric constant, nothing to do with the frequency of operation. You might well have problems

Re: [time-nuts] Thermal effects on cables

On Mon, 23 Jan 2017 15:13:39 + REEVES Paul wrote: > Surely the impedance of the cable is only affected by the ratio > of the inner conductor and outer conductor diameters modified by > the internal dielectric constant, nothing to do with the frequency of >

Re: [time-nuts] Thermal effects on cables

s [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David > Kirkby (Kirkby Microwave Ltd) > Sent: 23 January 2017 13:26 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Thermal effects on cables > > On 13 January 2017 at 06:52, Ole Pette

Re: [time-nuts] Thermal effects on cables

Dave, the typical spec sheet for VNA cables have a very restricted "lab temperature" range specified. For example 23C +/- 5C. There's a very nice graph showing effect of flexure on phase stability in Fig 2 of this spec sheet:

Re: [time-nuts] Thermal effects on cables

...@febo.com] On Behalf Of Dr. David Kirkby (Kirkby Microwave Ltd) Sent: 23 January 2017 13:26 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thermal effects on cables On 13 January 2017 at 06:52, Ole Petter Ronningen <opronnin...@gmail.com> wrote: >

Re: [time-nuts] Thermal effects on cables

On 13 January 2017 at 06:52, Ole Petter Ronningen 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: >

Re: [time-nuts] Thermal effects on cables

On Fri, 13 Jan 2017 07:52:18 +0100 Ole Petter Ronningen wrote: > 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: >

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

May I suggest to turn the 24 hours reset period into a parameter? On Fri, Jan 13, 2017 at 8:45 PM, Tom Van Baak wrote: > Mark, Ole, > > Yes, averaging can both enhance precision but also destroy information. In > many cases too much data is a bad thing. The solution is to

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

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

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

Mark, Ole, Yes, averaging can both enhance precision but also destroy information. In many cases too much data is a bad thing. The solution is to add another dimension to the plot. Stable32 does this with DAVAR (dynamic Allan variance). TimeLab has a multi- "trace" feature. Both of these break

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

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 > wrote: > > That IS interesting.. It reads to me that the advice is to keep a "moving 300 > pt

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

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

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

You are certainly justified to be cautious of only using an xDEV for state of health. I don't know what GPS does for example to mark SV's as healthy or not healthy. On Fri, Jan 13, 2017 at 1:11 PM, Bob Camp wrote: > Hi > > I do agree with their point that systematics will get

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

Hi I do agree with their point that systematics will get buried in giant data blocks. What I’m not quite as sure of is the utility of even 300 sample blocks to spot systematic issues. Bob > On Jan 13, 2017, at 1:08 PM, Scott Stobbe wrote: > > I think you might be

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

I think you might be overthinking their point, that if you plan to use an xDEV as a measure for state of health, don't use years worth of data. Otherwise it could be days before the xDEV visually changes. On Fri, Jan 13, 2017 at 11:04 AM, Bob Camp wrote: > Hi > > There’s an

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

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

Re: [time-nuts] Thermal effects on cables

On 1/12/17 10:52 PM, Ole Petter Ronningen 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:

Re: [time-nuts] Thermal effects on cables

I should have mentioned this in the original post - the measurements were not taken on the same cable length. Beware, and consult paper. Ole On Fri, Jan 13, 2017 at 7:52 AM, Ole Petter Ronningen wrote: > Hi, all > > The question of phase shifts in cables pops up every