A prototype four-horn cluster IFF antenna

The experimental design of a prototype four-horn cluster IFF antenna is described. The antenna was evaluated for voltage standing wave ratio (VSWR), model antenna range patterns, and in-flight horizontal and banked aircraft radiation patterns. The data is presented to show that each antenna horn demonstrates isotropic gain within plus or minus 45 degrees of its azimuth pointing direction and a front to back ratio gain of about 20 db. The prototype antenna will provide an aircraft with improved and controlled coverage for reception of IFF signals and will limit the volume of space to which its replies are radiated.