Owen Duffy wrote:
(I used the term resolve, Cecil must
call it destructive interference.)

When two coherent waves superpose in an out-of-phase
manner, it is called destructive interference. When
two coherent waves superpose in an in-phase manner,
it is called constructive interference.

100V at 0 deg superposed with 50V at 180 deg equals
50V at 0 deg. That's destructive interference.

100V at 0 deg superposed with 50V at 0 deg equals
150V at 0 deg. That's constructive interference.

One can solve a mental example. Assume a 1/4WL 600
ohm open stub made from resistance wire such that
its impedance is 50 ohms. Apply a signal from a
piece of 50 ohm coax and analyze the conditions
at the physical 50/600 ohm impedance discontinuity.
One will get a good idea of what goes on with a
1/2WL dipole at the feedpoint.
--
73, Cecil http://www.w5dxp.com