Phase center distributions of spiral antennas

The phase center distributions of four types of equiangular spiral antennas were experimentally determined at a frequency of 3000 mc to enhance the general knowledge of these types of frequency independent antennas. The usual methods that are available for determining phase centers were considered. The two probe method for examining the far field wavefront was used. However, a new type of probe antenna was developed that is capable of being made very inexpensively for either horizontal or vertical polarization.