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
the number of bins to 300 for any particular tau you wish to monitor, you
will see the ADEV wonder up and down over time, but if it exceeds say 5
sigma, 25% something is up.

On Fri, Jan 13, 2017 at 12:30 PM, Ole Petter Rønningen <
opronningen@gmail.com> wrote:

On Fri, 13 Jan 2017 07:52:18 +0100
Ole Petter Ronningen opronningen@gmail.com wrote:

I would like to add here a couple of more references:

"Phaste stability of typical navy radio frequency coaxial cables",
by Rodriguez, 1965
http://www.dtic.mil/dtic/tr/fulltext/u2/628682.pdf

"Current Innovations In Phase Stable Coaxial Cable Design"
by Times Microwave Systems
https://www.timesmicrowave.com/downloads/tech/phasearticle.pdf

"Understanding Phase versus Temperature Behavior - The Teflon Knee",
by Micro Coax
http://www.micro-coax.com/wp-content/themes/micro_coax/includes/pdf/applications_notes/13-MIC-0012.Phase_vs_Temp_Behavior_FINAL.pdf

"Temperature Stability of Coaxial Cables",
by Czuba and Sikora, 2011
http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf

"Phase stable RF-cable for space applications"
by Karstensen et al. 2013
Poster: https://www.ethz.ch/content/dam/ethz/special-interest/mavt/design-materials-fabrication/composite-materials-dam/Research/Posters/067.pdf
Paper: https://escies.org/download/webDocumentFile?id=60894

		Attila Kinali

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

On 13 January 2017 at 06:52, Ole Petter Ronningen opronningen@gmail.com
wrote:

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.

Dave

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 :-)
Regards,

Paul Reeves

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@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@gmail.com
wrote:

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.

Dave

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi

Nothing is ever simple if you dig deep enough:

http://www.jensign.com/RG58U/

http://www.cliftonlaboratories.com/the_curious_case_of.htm

Bob

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:
https://www.gore.com/sites/g/files/ypyipe116/files/2016-07/GMCA-0224-DAT-US-MAY16_e.pdf

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

On Mon, Jan 23, 2017 at 8:26 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:

On Mon, 23 Jan 2017 15:13:39 +0000
REEVES Paul Paul.Reeves@uk.thalesgroup.com wrote:

If you are only looking at the impedance, then yes. But once you get
to high frequencies, you get also multi-mode behaviour of the coax cables
and connectors, which leads to dispersion. That's why people hardly use
N connectors for GHz frequencies, even though the connector itself would
allow it. For VNAs where even small phase shifts/instabilities due to
multi-mode behaviour/dispersion are a no go, the connectors are usually
3.5mm (basically a precise version of the SMA), 2.9mm, 2,4mm etc
and go down to even 1.0mm which can be spec'ed up to 110GHz.

BTW: the 3.5mm connector is one that you will find on many instruments
that go beyond 1-2GHz. Unfortunately it looks exactly the same as an
SMA connector and will mate with one. Even more unfortunately, mating
it with an SMA connector will scar the connector and most likely move
it out of spec (ie degrade it to a simple SMA connector). If it's just
an adapter, you've only lost a bit of money (in the order of a few €100).
If it was the connector of your VNA/oscilloscope/..., you might need to
send it in for an expensive repair.

		Attila Kinali

--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor

On 1/23/17 7:13 AM, REEVES Paul wrote:

I think the large outer diameter is essentially a soft armoring, which
limits the bend radius, which in turn limits the deformation of the
outer conductor and dielectric.

VNA test port cables also have very good shielding effectiveness as well
as stable propagation properties.

The underlying cable would have to be fairly small diameter, because
otherwise you'd get moding problems at high frequencies.  At 60 GHz, the
cable really has to be smaller than a few mm diameter.

On 1/23/17 9:16 AM, Bob Camp wrote:

here's my guess on the curious case cable: it was mismarked by accident
at the factory (e.g. 93 ohm coax, marked as 50 because someone forgot to
push the button on the marking machine), and dumped in the scrap bin,
and then sold by someone who bought the surplus and just read the markings.

Or, even sold as a whole spool, likely at a discount, to a
"knowledgeable buyer" who was willing to take it, mismarkings and all.

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