There are tons of references for cryogenic cases, but few at room
temperature. So I measured some.

https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1

These are rough numbers but useful for what I'm doing. I need to mount
an electro-optical modulator on a temperature-controlled block,
probably vibration isolated, and need to run four coaxes to it, two RF
and two bias.

On Fri, 11 Jun 2021 11:18:24 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>There are tons of references for cryogenic cases, but few at room
>temperature. So I measured some.
>
>https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>
>These are rough numbers but useful for what I'm doing. I need to mount
>an electro-optical modulator on a temperature-controlled block,
>probably vibration isolated, and need to run four coaxes to it, two RF
>and two bias.

Be aware that thin coax hardlines are usually Teflon-insulated, and so
suffer from the "Teflon knee" effect, where the electrical length
changes abruptly around 20 C (crystal structure phase change). Don't
know if this matters in your application. If the cables are short,
the effect is small.

The good news is that Teflon can be run a good bit hotter than
polyethylene et al.

Joe Gwinn

John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> There are tons of references for cryogenic cases, but few at room
> temperature. So I measured some.
>
> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>
> These are rough numbers but useful for what I'm doing. I need to mount
> an electro-optical modulator on a temperature-controlled block,
> probably vibration isolated, and need to run four coaxes to it, two RF
> and two bias.
>

Calculate thermal resistand of inner and outer conductor and you have
a very good first estimate
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------

On Fri, 11 Jun 2021 18:21:48 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:

>On Fri, 11 Jun 2021 11:18:24 -0700, John Larkin
><jlarkin@highland_atwork_technology.com> wrote:
>
>>There are tons of references for cryogenic cases, but few at room
>>temperature. So I measured some.
>>
>>https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>
>>These are rough numbers but useful for what I'm doing. I need to mount
>>an electro-optical modulator on a temperature-controlled block,
>>probably vibration isolated, and need to run four coaxes to it, two RF
>>and two bias.
>
>Be aware that thin coax hardlines are usually Teflon-insulated, and so
>suffer from the "Teflon knee" effect, where the electrical length
>changes abruptly around 20 C (crystal structure phase change). Don't
>know if this matters in your application. If the cables are short,
>the effect is small.
>
>The good news is that Teflon can be run a good bit hotter than
>polyethylene et al.
>
>Joe Gwinn

I mentioned the Teflon effect to my customer (who is providing my
trigger) and they'd never heard of it. And they are harassing me over
picoseconds.

My block will only run at 35 or 40C, so any cable should survive. I'll
probably measure prop delay of candidate cables vs temperature.

On 11 Jun 2021 22:51:30 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:

>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> There are tons of references for cryogenic cases, but few at room
>> temperature. So I measured some.
>>
>> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>
>> These are rough numbers but useful for what I'm doing. I need to mount
>> an electro-optical modulator on a temperature-controlled block,
>> probably vibration isolated, and need to run four coaxes to it, two RF
>> and two bias.
>>
>
>Calculate thermal resistand of inner and outer conductor and you have
>a very good first estimate

I measured the electrical resistance of the shield and multiplied by
150,000. Close enough.

Maybe I can find some super tiny cable for the bias signals, which are
slow and drive the hi-z part of the EOM.

John Larkin wrote:
> On Fri, 11 Jun 2021 18:21:48 -0400, Joe Gwinn <joegwinn@comcast.net>
> wrote:
>
>> On Fri, 11 Jun 2021 11:18:24 -0700, John Larkin
>> <jlarkin@highland_atwork_technology.com> wrote:
>>
>>> There are tons of references for cryogenic cases, but few at room
>>> temperature. So I measured some.
>>>
>>> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>>
>>> These are rough numbers but useful for what I'm doing. I need to mount
>>> an electro-optical modulator on a temperature-controlled block,
>>> probably vibration isolated, and need to run four coaxes to it, two RF
>>> and two bias.
>>
>> Be aware that thin coax hardlines are usually Teflon-insulated, and so
>> suffer from the "Teflon knee" effect, where the electrical length
>> changes abruptly around 20 C (crystal structure phase change). Don't
>> know if this matters in your application. If the cables are short,
>> the effect is small.
>>
>> The good news is that Teflon can be run a good bit hotter than
>> polyethylene et al.
>>
>> Joe Gwinn
>
> I mentioned the Teflon effect to my customer (who is providing my
> trigger) and they'd never heard of it. And they are harassing me over
> picoseconds.
>
> My block will only run at 35 or 40C, so any cable should survive. I'll
> probably measure prop delay of candidate cables vs temperature.
>

Teflon's mechanical properties go all over the shop at the glass
transition, but the dielectric properties don't. So if you've got a
bunch of mechanical stress due to bending, say, I expect it'll relax all
at once at T_g, causing mechanical motion that may be quite noticeable.
However, it ought to stay still after that if it's undisturbed.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 6/11/2021 7:32 PM, John Larkin wrote:
> On 11 Jun 2021 22:51:30 GMT, Uwe Bonnes
> <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
>
>> John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>> There are tons of references for cryogenic cases, but few at room
>>> temperature. So I measured some.
>>>
>>> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>>
>>> These are rough numbers but useful for what I'm doing. I need to mount
>>> an electro-optical modulator on a temperature-controlled block,
>>> probably vibration isolated, and need to run four coaxes to it, two RF
>>> and two bias.
>>>
>> Calculate thermal resistand of inner and outer conductor and you have
>> a very good first estimate
> I measured the electrical resistance of the shield and multiplied by
> 150,000. Close enough.
>
> Maybe I can find some super tiny cable for the bias signals, which are
> slow and drive the hi-z part of the EOM.
>
As you just pointed out and I'm sure many noticed, the thermal
conductivity is proportional to the resistance.

 I assume these are all copper shield material.

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

On Sat, 12 Jun 2021 08:55:22 -0500, amdx <amdx@knology.net> wrote:

>On 6/11/2021 7:32 PM, John Larkin wrote:
>> On 11 Jun 2021 22:51:30 GMT, Uwe Bonnes
>> <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
>>
>>> John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>>> There are tons of references for cryogenic cases, but few at room
>>>> temperature. So I measured some.
>>>>
>>>> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>>>
>>>> These are rough numbers but useful for what I'm doing. I need to mount
>>>> an electro-optical modulator on a temperature-controlled block,
>>>> probably vibration isolated, and need to run four coaxes to it, two RF
>>>> and two bias.
>>>>
>>> Calculate thermal resistand of inner and outer conductor and you have
>>> a very good first estimate
>> I measured the electrical resistance of the shield and multiplied by
>> 150,000. Close enough.
>>
>> Maybe I can find some super tiny cable for the bias signals, which are
>> slow and drive the hi-z part of the EOM.
>>
>As you just pointed out and I'm sure many noticed, the thermal
>conductivity is proportional to the resistance.
>
>  I assume these are all copper shield material.

The semi-flex ones are tinned braided copper.

The 150K factor is pretty good for most metals. Some alloys seem to be
higher, so the tinned braid might be even higher theta. I'd want to
use flexy stuff for the bias runs anyhow.

Something like this:

https://www.dropbox.com/sh/ai3f96yxa8huj5n/AABNqgU6fJmygUjWqtwbbQk4a?dl=0

The 3gshielding gap-pad stuff is wonderful. It's soft and compressible
and flows around parts, and is about 5 w/m-K or so.

--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.

On Fri, 11 Jun 2021 17:27:59 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>On Fri, 11 Jun 2021 18:21:48 -0400, Joe Gwinn <joegwinn@comcast.net>
>wrote:
>
>>On Fri, 11 Jun 2021 11:18:24 -0700, John Larkin
>><jlarkin@highland_atwork_technology.com> wrote:
>>
>>>There are tons of references for cryogenic cases, but few at room
>>>temperature. So I measured some.
>>>
>>>https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>>
>>>These are rough numbers but useful for what I'm doing. I need to mount
>>>an electro-optical modulator on a temperature-controlled block,
>>>probably vibration isolated, and need to run four coaxes to it, two RF
>>>and two bias.
>>
>>Be aware that thin coax hardlines are usually Teflon-insulated, and so
>>suffer from the "Teflon knee" effect, where the electrical length
>>changes abruptly around 20 C (crystal structure phase change). Don't
>>know if this matters in your application. If the cables are short,
>>the effect is small.
>>
>>The good news is that Teflon can be run a good bit hotter than
>>polyethylene et al.
>>
>>Joe Gwinn
>
>I mentioned the Teflon effect to my customer (who is providing my
>trigger) and they'd never heard of it. And they are harassing me over
>picoseconds.

I suspected the part about picoseconds.

>My block will only run at 35 or 40C, so any cable should survive. I'll
>probably measure prop delay of candidate cables vs temperature.

If your stuff is always above 25 C while in operation, you won't see
the knee effect. The customer cables coming to your stuff may be
another issue. I assume that your requirements are worded such that
the delivery cables are not your problem.

Hmm. Any idea how long these delivery cables are?

Coaxial cables insulated with foamed polyolefin have no such knee.

I assume that the relevant cables in your product are less than a foot
in length.

The small-diameter rigid coax (solid copper shield, solid Teflon,
solid or stranded copper center) is actually pretty flexible, and is
easily formed by hand, or in a wooden form if multiple assemblies will
be made. One can hand wind baluns using such coax insulated with a
heat-shrink outer jacket (needed to prevent shield-to-shield shorts).

Joe Gwinn

On Fri, 11 Jun 2021 21:18:33 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>John Larkin wrote:
>> On Fri, 11 Jun 2021 18:21:48 -0400, Joe Gwinn <joegwinn@comcast.net>
>> wrote:
>>
>>> On Fri, 11 Jun 2021 11:18:24 -0700, John Larkin
>>> <jlarkin@highland_atwork_technology.com> wrote:
>>>
>>>> There are tons of references for cryogenic cases, but few at room
>>>> temperature. So I measured some.
>>>>
>>>> https://www.dropbox.com/s/yvwgbmm9moiyiue/Coax_Thermals.jpg?raw=1
>>>>
>>>> These are rough numbers but useful for what I'm doing. I need to mount
>>>> an electro-optical modulator on a temperature-controlled block,
>>>> probably vibration isolated, and need to run four coaxes to it, two RF
>>>> and two bias.
>>>
>>> Be aware that thin coax hardlines are usually Teflon-insulated, and so
>>> suffer from the "Teflon knee" effect, where the electrical length
>>> changes abruptly around 20 C (crystal structure phase change). Don't
>>> know if this matters in your application. If the cables are short,
>>> the effect is small.
>>>
>>> The good news is that Teflon can be run a good bit hotter than
>>> polyethylene et al.
>>>
>>> Joe Gwinn
>>
>> I mentioned the Teflon effect to my customer (who is providing my
>> trigger) and they'd never heard of it. And they are harassing me over
>> picoseconds.
>>
>> My block will only run at 35 or 40C, so any cable should survive. I'll
>> probably measure prop delay of candidate cables vs temperature.
>>
>
>Teflon's mechanical properties go all over the shop at the glass
>transition, but the dielectric properties don't. So if you've got a
>bunch of mechanical stress due to bending, say, I expect it'll relax all
>at once at T_g, causing mechanical motion that may be quite noticeable.
>However, it ought to stay still after that if it's undisturbed.
>
>Cheers
>
>Phil Hobbs

This is cool, especially page 2.

https://tinyurl.com/2u3mmmth

and

https://tinyurl.com/pjteuj5h

I'm working with a system that provides us timing info through two
paths, an electrical 10 MHz sinewave clock and an optical fast trigger
pulse.

Should be fun. Coax and fiber delay tempcos have the opposite sign!

--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.