[TowerTalk] Rig on Second Floor - Grounding
Jim Brown
jim at audiosystemsgroup.com
Sun Aug 26 00:02:50 EDT 2007
On Sat, 25 Aug 2007 20:52:10 -0400, D. Scott MacKenzie wrote:
>Now should I also have a separate counterpoise
>for the RF ground?
I don't understand the question. A "counterpoise" is part of an
antenna -- it provides a return path for antenna current in
single-ended antennas (like verticals and long wires). That has
NOTHING to do with ground or the earth. Indeed, the EARTH is quite
lossy, and makes a lousy counterpoise. That's why we use radials
if we need a return path for antenna current.
You said you plan for him to use a 20M dipole. A dipole is a
completely self-contained antenna -- the current flows from one
half of the antenna to the other (and back). Ground is not in that
path. Indeed, there's no place to connect a counterpoise.
There is a long-standing myth that radio systems need to be
grounded to work, or to be noise-free, or to prevent RFI. It is
one of those lies that has been repeated so often that it is
almost universally believed. Virtually every radio instruction
manual I've ever seen repeats the lie. But it is totally false.
The only (good) reason for connecting a radio or antenna to the
EARTH is lightning protection.
73,
Jim Brown K9YC
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