The Field of a Dipole with a Tuned Parasite at Constant Power

Theoretical curves are shown of the electric field in the forward direction and in the backward direction for a center-driven half-wave dipole in the presence of a parallel center-tuned parasite of the same length and radius. The ratio of the electric field of the two-antenna array to the field of the driven unit alone at constant power is given as a function of the distance b between the antennas in the range from b = 0 to b = λ0, for both the forward direction (the parasite is a reflector) and the backward direction (the parasite is a director). The total reactance of the parasitic antenna is used as a parameter in the form X22= Xs2+ X2where Xs2= Xs1, is the self-reactance of the parasite in the presence of the identical, driven dipole and X2is the tuning reactance at the center of the parasite. Values for which curves are shown are X22= 20, 10, 0, -10, -20 ohms and X22= Xs2or X2= 0. Reactances and resistances used are those of the first-order King-Middleton-Tai theory.