Art, KB9MZ wrote:
"---special thanks to the earlier posters who added more insight to the
values of Q."

Art`s posting is a misrepresentation of the way antennas work in my
opinion. Q of an antenna from an impedance standpoint is related to how
narrow its bandwidth is over a small frequency range. Its Q at resonance
is:

2 pi x total energy stored by antenna / energy dissipated per cycle.

Attempts to maximize gain while minimizing size of an antenna generally
reduce its bandwidth while also reducing its radiating efficiency. See
"Antennnas" by Kraus, 1950, pages 433-434.

Coupling is another word for mutual impedance. The mutual impedance
between two antennas is defined by:

Z12 = E2/I1.

This is the ratio of the voltage induced in antenna #2 by the current in
antenna #1. See Terman`s 1955 edition page 894 for details.

Antennas or elements of arrays can be coupled and must be if a parasitic
array is to be effective. Spacing and tuning of the elements is
essential to performance. Unless elements are near resonance, reactance
is too high for significant current flow. Also, which side of resonance
parasitic elements are tuned to determines which direction radiation
will be reinforced in and in which direction radiation from the direct
radiator and re-radiation from the parasite will tend to cancel.

Terman says on page 905 of his 1955 edition:
"The exact effect on the directional pattern that is produced depends
upon the magnitude and phase of the induced current, i.e., upon the
spacing of the antennas and upon the tuning of the parasitic antenna.
For example, if the driven and parasitic antennas are relatively close
together and parallel, then the current induced in the parasitic antenna
will be such as to reduce the strength of the radiation in the direction
of the parasitic antenna when the latter is resonant at a lower
frequency than that being transmitted. If resonant at a higher frequency
than is being transmitted, the parasitic antenna acts as a "director"
and tends to concentrate the radiated field in its direction."

The information above all came from books by famous authors. We can`t
and don`t live long enough to make all the mistakes for ourselves.

Best regards, Richard Harrison, KB5WZI