On Sun, 7 Jan 2007 19:17:55 -0000, "David" nospam@nospam wrote:

Various books claim that a ground plane reflects the radio wave emitted by
the vertical, and then claim that a ground plane is formed or simulated by
four elevated radials.
I emailed two Professors of antenna theory about this.

Reply from Professor Constantine Balanis:
"The radials should act more as a ground plane. Four of them are usually the
minimum. The more of them, the better the ground plane. The objective of the
ground plane is to reflect the energy from the main element; the vertical
wire".


Hi David,

This is becoming tiresome by half.

"Quotes" that do not have a context (what was the question asked?) are
more name dropping than an informed discussion. It is also called
shopping for testimony.

"Does a ground plane reflect?" This is a loaded question much like
"Have the Republicans offered a balanced budget?" Each question can
be so heavily qualified as to guarantee success and bragging rights.
Each can be so heavily doped up on the narcotic of self-indulgence as
to offer only the prospects of a somnambulistic nod of affirmation.

If one conspired to erect a 2M vertical on the radial field of a
former AM station; then, yes, these radials reflect admirably. If one
takes the same 2M vertical (as shipped from, say, Comet) and looked at
the reflection components of its radials; then, yes, these radials
reflects, but with less than pedestrian results. Difference is found
in the application. The AM station ground field will produce more 2M
reflection contacts to the horizon, the standard radials of a 2M Comet
will have indifferent reflection contacts oriented towards satellites.

Simple modeling and analysis reveals this in less than an hour's work.

More effort in the field confirms the modeling and analysis.

Modeling and analysis conform to every expectation offered by all the
authors quoted, given they use the same tools and were, perhaps,
instrumental in their development.

The "Image" theory relates to reflections found in the far field
beyond the physical extent of practical radials. To force the
standard implementations of radials into supporting this theory (to
the exclusion of the greater application), debases the intent of the
theory. Actually, to call it a theory is painting the rose and
gilding the lily. This tarted up observation is used mainly to soothe
the troubled minds of neophytes until they become accustomed to
dealing with larger, more involved problems. It is a suitable
metaphor; however, metaphors are the weakest form of argument as they
often fail early on close examination.

73's
Richard Clark, KB7QHC