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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: Dressing RG6
Date: Wed, 15 May 2024 23:24:28 +0200
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On 5/15/24 17:06, John Larkin wrote:
> 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.
> 

I didn't?

Jeroen Belleman