[time-nuts] Thermal effects on cables

REEVES Paul Paul.Reeves at uk.thalesgroup.com
Mon Jan 23 10:13:39 EST 2017

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 converting the larger diameters down to a suitable size for the connectors at the higher frequencies though....
I thought that the HP cabling for the 8510 series VNAs was air spaced but I might well be wrong - I just tried not to damage them :-)

Paul Reeves

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at 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 <opronningen at gmail.com>

> 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.
I've like to know how VNA cables compare. They are expensive enough - a couple of cables around 600 mm long (24") for my VNA are over $5000. They are much larger diameter than normal cables, but much more flexible too.
The construction is obviously very different. Since mine are designed for use to 26.5 GHz, the internal diameter of the outer conductor can be no more than a couple of mm, yet the overall cable has a diameter of about 15 mm.

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