Out-of-band response of VHF/UHF airborne antennae

Abstract

The out-of-band response of an antenna is an important factor in determining the receiving system's susceptibility to the RF environment in which it is required to operate. A method for measuring the response of antennas below band is presented that is reliable, repeatable, and simulates to a high level of confidence plane wave conditions-the actual propagation mode that all airborne communication/navigation (COMM/NAV) antennas sense from most ground emitters and broadcast stations. The method has shown that the gain of most airborne COMM/NAV antennas is approximately -60 dBi, in the higher frequency range, to -120 dBi, in the lower frequency range, depending on the antenna. The VHF Whip antenna presents higher gain, due to its mechanical dimensions.<>