John Smith wrote:
"Oh yes, the important spacing--"

Proximity determines induction in a parasiteic element. Far from an
energy source, the parasite captures little energy and re-radiates
little. The mutual impedance between elements is small when spacing is
large.

A parasite must be nearly resonant to become excited. Behavior is
similar to a reed in a resonant-reed frequency indicator. The resonant
reed is strongly excited. Other reeds are little excited at the wrong
frequency. An out of tune antenna element has its current impeded by
reactance. A resonant element has no reactance.

Detuning a parasitic element is slight if excitation is to be
maintained, but it is enough to make the element reflect or direct as
desired.

Magnetic fields are naturally produced around current-carrying
conductors and around displacement currents too. Electric and magnetic
force lines are mutually perpendicular. In space, the plane containing
crossed electric and magnetic lines is called the wave front. Travel
direction of the front is perpendicular to the crossed electric and
magnetic lines.

Wave theory accurately predicted radio behavior before anyone thought of
acceleration causing photon emissions.

Best regards, Richard Harrison, KB5WZI