An antenna, also called an aerial, is a device made of metal rods and wires and sometimes other materials. The word comes through Latin from Greek, in which it referred both to an insect’s sensory appendages as well as to a yardarm, a spar attached to a mast to support a sail, and therefore sticking out of the mast at an angle, similar to the way an antenna protrudes from an insects head. The purpose of an antenna is to radiate and receive radio signals. Antenna basics include the fundamentals of how antennas work, the main uses to which antennas are put, and the main types of antennas.
Antenna basics of how antennas work includes the recognition that antennas can either be devoted solely to reception or to transmission or perform both tasks. Transmitting antennas convert electrical current into electromagnetic radio waves and project them into space. Receiving antennas, on the other hand, convert electromagnetic waves back into electrical current. Antennas that both receive and transmit do both.
The main applications in which antennas are used is a second element of antenna basics. Television and radio antennas have long been used in many households. TV antennas are designed to receive the signals of broadcast television. Home radio antennas for AM and FM radio are used only for reception, while CB radios, ham radios, and two-way have antennas that can both receive and send signals. Other uses of antennas include wireless LAN (local area networks), cell phones, WiFI, GPS (Global Positioning System), and radar.
One of the other elements of antenna basics is the types of antennas. Besides being described by use, antennas are typed by their construction. Television antennas include dipole antennas — some of which are called rabbit ears, stacked dipoles, reflector antennas, log-periodic dipole arrays (LPDA), and Yagi antennas. Radio antenna types include the short so-called rubber duck antennas that, for example, come with portable CB radios; tower antennas; omni-directional/unidirectional antennas that change function according to orientation; and dipole antennas. CB antennas are made for base stations, mobile CB radios, and portable CB radios. Another way of typing antennas is by placement. There are indoor and outdoor antennas, and those mounted on building roofs, vehicles, and towers.
