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From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: Dressing RG6
Date: Wed, 15 May 2024 08:06:03 -0700
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On Wed, 15 May 2024 07:27:07 -0700, John Larkin
<jjSNIPlarkin@highNONOlandtechnology.com> wrote:

>On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
><jeroen@nospam.please> wrote:
>
>>On 5/15/24 01:33, Don 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?
>>
>>Both ends were connected to the connector shields. The point of
>>the exercise was to reduce transfer impedance, which at low
>>frequency (<1MHz) is simply proportional to screen resistance.
>>
>>Jeroen Belleman
>
>Two parallel coaxes can make an attenuator.
>
>What was the coupled frequency response like?

Just say your data below.