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For a VLF flat-top antenna much smaller than the radian sphere (a sphere whose radius is one radianlength), the effective height, effective area, and effective volume are defined. The required power factor of radiation proportionately determines the effective volume. For a specified power to be radiated, the effective height inversely determines the current and the effective area inversely determines the voltage. For a limited electric gradient on the overhead wires, the current requires a proportionate area of conductor surface. A corresponding total length of wire in the flat top is adequate if disposed for uniform distribution of charge and if spread out to realize the required effective area. These objectives are obtained more readily by some configurations, such as long parallel wires or concentric circles of wire. This study has been made for the U. S. Navy's high-power transmitter to be located in Maine, the first to radiate 1 megawatt continuously at 15 kc.
Date of Publication: January 1958