Would you agree that the earth is considered a zero potential reference
point when compared to things located on or flying above it ?
Would you agree that is true for both DC and AC ?
Would you agree that multiple paths in parallel, each with a finite
resistance, provide a smaller collective resistance (I should say impedance)
when connected in parallel ?
Would you agree that lightning is mostly RF ?
73 de Gary, AA2IZ
----- Original Message -----
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, April 04, 2009 12:35 AM
Subject: [TenTec] RF Ground
>
Do recall that any station ground has length and inductance and
impedance.
It may be a good DC ground as it has low resistance, but is it a good RF
ground? In almost any condition, the station is above RF ground. For
example, a station ground that is some 16 ft in length puts the station
at
1/4 wave above ground on 20M. That 1/4 wave ground wire can radiate or
receive noise just like an antenna.
The words "RF ground" have NO MEANING in science. They are a fignewton
of fuzzy thinking. A connection to EARTH is totally irrelevant for a
radio transmitter, receiver, or antenna. A connection to earth is NOT
part of a solution to RF interference, hum, buzz, or noise. A
connection to earth does not make an antenna work better. It only
provides lightning protection. That's very important, of course, and
to do that, ALL ground rods must be bonded together by that low
impedance path, and all wiring that enters a building must have its
lightning protection bonded together and to that network of ground rods.
For two reasons, that bonding together also minimizes hum and buzz
related to the power system.. First, pin 1 problems. Second, unbalanced
wiring. Both couple noise current into equipment.
The EARTH is a LOUSY antenna element, because it is lossy (resistive).
Any RF current flowing in the earth is lost as heat. We use radials with
vertical antennas to prevent current from flowing in the earth, and
allow it to flow in low resistance copper instead. The vertical antenna
is trying to produce an EM field, and the radials complete the path for
that field (and for the antenna current). Only a few resonant radials
can serve that purpose if they are high above the earth, but it takes
MANY radials to do that well if they are very close to the earth. Those
radials are not RF GROUND. Over the years, we have confused ourselves by
calling them a ground system, or a "ground plane." They are not. They
are part of the antenna!
73,
Jim Brown K9YC
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