On Sun, 24 Jul 2005 16:36:15 +0100 (BST), Roger Parsons wrote:
>there is always an external field even with perfectly shielded
>coaxial cable.
What do you mean by "perfect?" Perfect means that there would be no
external field, perfect uniformity of shield current around the
circumference of the shield, no "holes" in the shield, and implies a
solid shield like hardline.
It is also well known that, thanks to skin effect, at radio
frequencies, SIGNAL current tends to flow on the inside of a coaxial
shield, and NOISE current (that is, current due to external
excitation) tends to flow on the outside of the shield.
Jim Brown K9YC
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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