DIRECTIONAL ANTENNA. An antenna having the property of radiating or receiving radio waves in larger proportion along some directions than others. A directional antenna used as a transmitting antenna is sometimes called a "directive antenna." If the angle within which the radiation is substantially confined is a small one, the antenna may appropriately be described as a "beam antenna." A type of antenna known as a "coil antenna" consisting of one or more complete turns of wire has directional characteristics and has the property of radiating or receiving radio waves in larger proportion in angular regions 18o° apart than in other directions. One type of directional receiving antenna used particularly at low radio frequencies consists of a comparatively low horizontal aerial having a physical length of the same order of magnitude as that of the signaling waves to be received. Such an antenna is known as a "wave antenna."