VHF horizontally-polarized antennas for aircraft

Apart from a few military applications, the only VHF horizontally-polarized systems in general use on aircraft are those for the navigation aids ILS (instrument landing system) and VOR (VHF omni-range). As these are used on all but the smallest civil aircraft and on many military ones, antenna solutions have been produced for a wide range of aircraft size and shapes. Two classes of antennas are discussed, giving omniazimuth and directional coverage respectively