Gene Fuller, W4SZ wrote:
"As expected from the simple mirror image model there is complete far
field cancellation in the phi = 0. theta = 0 direction."

Right. Real and virtual imaqges are equidistant and 180-degrees out of
phase perpendicular to the reflector.

The more distant the radiator from the reflector, the smaller its image
appears. The phase difference between the radiator and its image varies
with the distance between them.

At 1/2-wavelength from the reflector, a round-trip takes 360-degrees and
leaves the phase unchanged. However, the reflection inverts the phase.
Incident and reflected waves cancel perpendicular to the reflector.

Two antenna elements, or one with its image in a reflectoe, will be
directional. An unobtainable isotropic is the reference, so te antenna
has gain.

There is no way to mount a J-pole next to a tower and preserve its omni
characteristics. The question is which directions would you favor and
which would you diminish?

You know the tower may be impenetrable, and the vector sum of incident
and reflected signals directly opposite the tower depends on the antenna
to tower spacing.

An antenna modeling program should be able io show you your options.

You know thet 1/2-wave spcing cancels in the diretion of the antenna
mounted on the tower face. Add or subtract a 1/4-wave to the spacing,
and the incident and reflected waves reinforce instead of cancel. As I
think Roy said, you pay your money and take your choice.

Best regards, Richard Harrison, KB5WZI