ORIGINAL MESSAGE:
On Fri, 19 Mar 2010 12:37:41 -0400, "Gary Schafer"
<garyschafer@comcast.net> wrote:
>
>What do you think happens when you use a tube for an antenna element?
>The whole element is charged. If you connect the feed line to only the front
>side of the element there is still current on the back side of it.
>How do you think the current gets around to the other side?
>
>But try to measure the current on the inside of the tube. You will find
>none!
REPLY:
You raise an interesting question about current in a tube as opposed
to a solid rod. In a sire or solid rod, the skin effect current is
only present on the skin. In a tube however, I'm not so sure there is
no current on the inner surface of the tube because that is also a
skin. The issue is complicated because any skin current on the inside
of the tube also "sees" the other side of the tube, unlike with a flat
sheet where there is no other side. So that issue remains to be
proven.
Because a sheet has two "skins", and has no other side like a tube
does, current flows on both "skins" of a sheet because it is repelled
from the center. When one drains off current from one skin, the
repulsion no longer exists and it is immediately replenished by
current from he other side. Otherwise my load padder caps would not
be connected to my load variable cap.
Fascinating discussion.
73, Bill W6WRT
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