[time-nuts] TAPR TICC boxed
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Tue Apr 4 07:23:05 EDT 2017
http://www.spacetechexpo.eu/assets/files/2015/Recent-Developments-in-Phase-Stable-Cables.pdf
is a more readily accessible source of data on coax cable delay tempco et.
Bruce
>
> On 04 April 2017 at 00:13 Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
>
> Copper jacketed low density PTFE insulated coax cables typically exhibit a net phase change of over 1000ppm during the PTFE phase transition. See figure 2 p14 of the Cables and connectors supplement to March 2017 microwave journal. Solid PTFE insulated cables exhibit an even greater (2 -3x) phase change. to achieve a phase shift tempco of 10ppm/C either hermetically selaed silicon dioxide powder insulated coax or "phase tracking" semirigid or better phase tracking flexible coax is required.
>
> Bruce
>
> > >
> > On 03 April 2017 at 21:22 Attila Kinali <attila at kinali.ch> wrote:
> >
> > On Mon, 3 Apr 2017 15:05:55 +1200 (NZST)
> > Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> >
> > > > >
> > > > > > >
> > > > For even more fun you could try to detect the PTFE phase change at around 20C using a cable with PTFE dielectric.
> > > >
> > > > This will require several 100 meters of cable to be measureable with
> > > > the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase
> > > > stable cables reach even <1ppm/K. Measuring a change of 10ppm with
> > > > a resolution of 60ps means that the delay has to be in the order of 6µs,
> > > > which is close to 1000m of cable. Even if dithering gives another facor
> > > > of 10, this still means 100m of cable.
> > > >
> > > > > > >
> > > > >
> > For this level of comparison I would suggest to use a sinusoidal signal,
> > instead of a pulse, and do phase comparison, which gives a resolution
> > in the order of 1ps with very little effort, thus reducing the required
> > cable length to 10-20 meters.
> >
> > Attila Kinali
> >
> > [1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011
> > http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf
> >
> > --
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