An Ultra-Wideband Bicone Antenna

An ultra-wideband bicone antenna is developed to cover the 25 MHz to 6 GHz frequency band with a minimum gain at the horizon greater than -5 dBi (>100 MHz) to -10 dBi (25-100 MHz) over this frequency range and a VSWR falling between 2:1 and 3:1. This bicone has a radiating aperture that is 2 inches in diameter and 44 inches long. The novel feature of this design is the bicone is much less than a half wavelength (236 in.) at 25 MHz. To achieve this reduction in size and still maintain the desired VSWR, the bicone characteristic impedance is designed to be 306 Omega, much higher than the 50 Omega, impedance of a typical coaxial feed line. This paper demonstrates the advantages of such high impedance bicones and shows an inexpensive technique for broadband matching the bicone to the coaxial feed line