The elements are given the correct lengths and spacings so that the radio waves radiated by the driven element and those reradiated by the parasitic elements all arrive at the front of the antenna in phase, so they superpose and add, increasing signal strength in the forward direction.
32.
So one could as well model the operation of the parasitic element as the superposition of a dipole element receiving power and sending it down a transmission line to a matched load, and a transmitter sending the same amount of power up the transmission line back toward the antenna element.
33.
There is a single driven element driven in the center ( consisting of two rods each connected to one side of the transmission line ), and a variable number of parasitic elements, a single " reflector " on one side and optionally one or more " directors " on the other side.
