Control of Radiating Properties of Antennas

A system of tuning is described by which the current distribution and therefore the radiating properties of an antenna, may be varied over an extremely wide range. This is effected by means of a localized capacity and inductance connected to the top of the radiator. The capacity may conveniently take the form of a sphere, a cylinder, or a disk. The inductance may take the form of a coil housed within the sphere or cylinder or it may consist of two parallel wires so adjusted for length as to supply the necessary inductive component. By appropriate adjustment the current distribution may be varied at will. The advantages are: (a) Increased radiation efficiency of antennas for any given length; (b) control of radiation angle and consequently the distance at which fading may become important; and (c) reduction of ground losses. The system is believed to be particularly adaptable to frequencies between 500 and 300,000 kilocycles.