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

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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 = λ 0 , 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 X 22 = X s2 + X 2 where X s2 = X s1 , is the self-reactance of the parasite in the presence of the identical, driven dipole and X 2 is the tuning reactance at the center of the parasite. Values for which curves are shown are X 22 = 20, 10, 0, -10, -20 ohms and X 22 = X s2 or X 2 = 0. Reactances and resistances used are those of the first-order King-Middleton-Tai theory.