AndyS wrote:

Andy asks:
Roy, is the field radiated by the parasitic element shifted in phase
relative to the incident field. If not, what determines the phase
shift ?

Yes, it can be different in both phase and magnitude, determined by the
length and diameter of the parasitic element. That's what you're doing
when you adjust the lengths of the elements of a Yagi -- adjusting the
phase and amplitude of the re-radiated fields from the elements.

Roy Lewallen, W7EL