I don't have any personal data to validate this, but W8JI, N6BT and
others have claimed that verticals with modest numbers of low elevated
radials have increased losses when there is also a path to earth (e.g. a
ground rod) from the common junction of the radials. That's one reason
that a common mode choke is often recommended between the antenna &
elevated radials and the feedline, which then allows the feedline shield
to be connected to earth.
This does seem to be less than optimum situation for lightning, however.
Apparently, there is less potential loss with increasing numbers of
radials, which lowers the RF voltage at the radial junction and the
percentage of the displacement current flowing in the dirt.
73, Terry N6RY
On 2009-03-16 8:31 AM, Jim Brown wrote:
> No. A radial system prevents current flow in the earth by
> providing a much lower impedance path for that current. It also
> provides capacitive coupling to the earth for lightning, so it can
> improve lightning protection. For a lot of reasons, the best
> situation by far is to have all the grounds in any installation
> bonded together by a very low impedance path (beefy and short).
> And it also is generally best for minimizing receive noise.
>
> 73,
>
> Jim K9YC
>
> --Original Message Text---
> From: RLVZ@aol.com
> Date: Mon, 16 Mar 2009 11:20:31 EDT
>
> Hi Guys,
>
> I sure enjoy the great information shared on TT!
>
> Question: since "The purpose of radials is to PREVENT transmitter current
> from flowing in the earth"
> then for better radiation efficiency would it be better to have the radials
> isolated from the lightning
> ground?
>
> 73,
> Dick- K9OM
>
>
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