Increased capacitance for VLF umbrella antennas using multiple-wire rib construction

Umbrella antenna configurations are used to top-load electrically short monopole antennas to increase effective height for efficiency and to decrease capacitive reactance for tuning purposes. A technique for obtaining larger effective height and capacitance for a given antenna configuration, which uses multiple-wire structural members to increase the effective antenna surface area, is proposed. The results of scale-model, theoretical, and experimental investigations for a 300-foot umbrella antenna are presented. A capacitance increase of 24 percent is obtained for the case of a 1 to 18 increase in antenna rib diameter.