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From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: Dressing RG6
Date: Tue, 14 May 2024 17:31:17 -0700
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On Tue, 14 May 2024 23:33:35 -0000 (UTC), "Don" <g@crcomp.net> wrote:

>Jeroen Belleman wrote:
>> Phil Hobbs wrote:
>>> John Larkin wrote:
>>>> Don wrote:
>
><snip>
>
>>>>> The parasitic capacitance created between coax and its metal armor can
>>>>> open a Pandora's box of potential problems.
>>>>
>>>> Capacitance between the coax outer and the copper pipe? Proper coax
>>>> shouldn't have any external field.
>>>
>>> If the whole system is really coaxial, that’s true. Leaky shields, ground
>>> loops, and so on, will modify that.
>>>
>>> Depending on the application, you may or may not care.
>>> If the whole system is really coaxial, that’s true. Leaky shields, ground
>>> loops, and so on, will modify that.
>>>
>>> Depending on the application, you may or may not care.
>>
>> I've been putting coax inside copper tubes or braids to measure
>> and/or reduce the transfer impedance (leakage). I did that to
>> measure small signals in a particle accelerator, which typically
>> has kicker magnets and RF cavities with kA currents and kV
>> voltages nearby.
>>
>> A colleague developed a special low transfer impedance coax
>> cable for this sort of application. It had two screens with
>> intermediate magnetic shielding. It was unpleasant to work
>> with, because part of the magnetic shielding was a steel
>> spiral foil tape that was razor sharp. But it worked really
>> well.
>
>Empirical observation always trumps theory for me. Did you ground [1]
>the copper tubes or braids?
>
>Note.
>
>[1] Whitlock cynicism can be ignored:
>
>    Q. What does "ground" mean?
>    A. A fantasy invented by engineers to simplify their work.
>
>    _An Overview of Audio System Grounding & Interfacing_
>    by Bill Whitlock
>
>Danke,

I means just what it says. Dirt.