On Fri, 21 Jan 2005 14:50:05 -0600, "Richard Fry"
wrote:

"Richard Clark" wrote
The transmission line being orthogonal is in the plane of the
dipole's null - hence zero conduction.
___________

But the nulls of a dipole are off its ends. The t-line connects to the
dipole center, where relative field normal to the longitudinal axis of the
dipole is at a maximum.

Hi OM,

It takes only a moment to visualize a dipole, frozen in time, where
each arm supports the opposite charge. The continuum of forces
between the two, in three-space, shows a distinct plane of response
where a net-zero force is exhibited. This reference plane, a virtual
ground, falls between the poles and is orthogonal.

A common artifice of erecting vertically polarized antennas above
dipoles bears this out. The two are invisible to each other. It also
allows for the use of towers to support beams, but also explains why
guy wires which violate balance (do not fall within the plane) must be
broken up as conductors. The towers have a smaller degree of coupling
than do the guy wires that support them.

Even folded dipoles in commercial installations make use of this
reference plane by providing a mounting point (180 degrees from the
feed) to the support structure. No regard needs to be made for
"shorting" out the loop at this point.

The null you speak of is exhibited in the far field - the utility of
BalUn/Chokes are in the near field. The transmission line may lie
within the reference plane, but its metallic connection to one of the
poles necessarily violates the electrical balance. The BalUn/Choke
isolates this connection.

73's
Richard Clark, KB7QHC