Low frequency performance of hemispherical coverage conical log-spiral antennas

The performance of a conical log-spiral antenna is examined with particular reference to the effects of varying the spiral constants of the antenna, and the fundamental differences between two- and four-arm spirals are discussed. In order to extend the useful range of the antenna to frequencies below the frequency-independent range, reflections from the arm ends have been reduced by resistive loading; the deterioration in antenna parameters is then due solely to truncation of the active region. For both loaded and unloaded cases, good agreement is generally found between experiment and theory. Anomalies due