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Re: [TowerTalk] Double shield

To: <>, "VR2BrettGraham" <>
Subject: Re: [TowerTalk] Double shield
From: "Jim Lux" <>
Date: Tue, 12 Oct 2004 21:46:15 -0700
List-post: <>
> The "holes" in the braid of a piece of coaxial cable I see are often
> bigger than that in a mesh surface of a dish receiving C-band, if
> not Ku-band.  The mesh is like waveguide beyond cutoff & so are
> the holes in the braid.

Big difference between woven braid and perforated surfaces as far as EM
propagation goes...
Yes, the holes in the mesh are like WG past cutoff, but there's no conductor
penetrating the hole.  In a braid, there's conductors weaving in and out
through the holes.

It's like building screen rooms.. woven mesh bad: welded mesh good.

However, Tom's comments relating to the numerical difference are well taken.
In most applications, the difference between 60 and 100 dB isolation is
> Sure doesn't look right & filling those holes somehow should certainly
> make it better, or so we tend to think.


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