Topband: Elevated Radials
rfry at adams.net
Tue Mar 5 18:45:27 EST 2013
Guy Olinger posted:
>...The very same NEC 4.2 with raised quarter wave radials over routine real
>life ground made of dirt will show field intensities in the ground. (etc
Sorry, but this is a misunderstanding/misuse of NEC for this situation.
The r-f currents flowing in the earth under and near elevated, horizontal
radials are NOT the source for the r-f currents flowing on those radials,
themselves. Those radial wire currents are supplied by the currents flowing
on the inside surface of the outer conductor of a coaxial transmission line
used to drive the monopole -- which is connected to the common point of
those elevated radial wires.
Elevated radials behave much differently than buried radials. In effect,
driving a vertical monopole against an even number of geometrically-
symmetric pairs of at least two elevated, horizontal wires used as a
counterpoise converts a base fed (unbalanced) monopole radiator into a
balanced radiator -- which neither needs, nor can use a structural
connection to the earth for most efficient system performance.
For proof of this, please study the measurements of a real-world system
using 4 x 1/4-wave elevated radials described in the link below, for/at
WPCI, 1490 kHz in Greenville, SC, and the rest of that paper.
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