People like to simplify things, to make them easier to understand. They
read that radials are important, but don't understand why, and apply
that "sound bite" to all vertical antennas. (Or even to all antennas.)
This sort of binary thinking -- or rather, non-thinking, is commonly
applied to politics and a vast number of other fields besides antenna
theory.

When you put power into an antenna, a current flows out of one conductor
of the feedline to supply that power. An equal and opposite current
flows into the other conductor. In the case of a grounded vertical, this
means that whatever current flows into the base of the antenna also
flows through the ground -- where the feedline shield is connected. Due
to the resistance of the ground, this results in I^2 * R power loss. If
the antenna's radiation resistance is comparable to or lower than the
ground resistance, the fraction of applied power that's lost is
significant, so it's common to lower the ground resistance by using
radials. Radials become increasingly important as the vertical gets
shorter, because a short vertical has a lower radiation resistance.
However, the feedpoint radiation resistance of a half wave vertical is
very high -- typically higher than the ground resistance. For a given
power input, a relatively small current flows into the base of the
antenna, so very little current flows in the ground. Consequently, the
ground loss is low, and there's no need to decrease its resistance with
radials.

Roy Lewallen, W7EL

larry d clark wrote:

in a never ending quest to acquire antenna knowledge
i've been doing some reading of a paper back book
by a well know antenna guru who's now a sk.
he claims that if a vertical antenna is fed at it's base
with a parallel resonant l/c circuit and tapped on the
inductor to to get an appropriate swr match, it's
rf ground can be no more than a 3'x3' screen combined
with a rod in the ground.

in my mind, this seems to be something for nothing. if true
why do i read about the importance of having a number
of radials?

questions, comments, pronouncements from the gurus on high
most welcome. brickbats & complaints, etc 2&1 /dev/null

larry
kd5foy