Topband: "Missing" Buried Radials for a Monopole
w8ji at w8ji.com
Fri Aug 24 12:15:10 EDT 2012
> Do you think that radials --either elevated or laying on the ground--
> radiate? Or does all of the radiation come from the vertical monopole
> the radial system?
There is no question radials radiate, and it is impossible to stop them from
radiating or coupling to things around them, at least in the near field.
If they didn't radiate or couple, they couldn't do anything. :-)
> There is a recent thread about this on the antennex.com Antenna-discussion
> forum, which I originated. I tend to believe that while there is a local
> field around the radials, it does not go far. The far-field radiation only
> comes from the vertical portion.
There are three "fields" at work. Electromagnetic, which is a weak force but
unless cancelled goes on through space forever. Electric and magnetic
induction fields, which are rapidly decaying fields involved in local energy
storage and distribution.
The question is really all about proportions. Nothing cancels the EM field
from a single radial except earth reflection. Two radials can pretty much
cancel in the farfield, but not perfectly. Model a freespace groundplane
with two perfectly balanced radials. You will see the pattern distortion
caused by radial radiation.
Near earth, there is an "image" that helps cancel radiation, but it isn't
perfect. If it was perfect our Beverages would not work as Beverages. If the
image was missing our ewe and flag antennas would not work nearly as well.
We have to watch making things black and white.
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