See Also: Omnidirectional Antenna, Horizontally Collinear Antenna, Yagi Antenna, Corner Reflector Antenna, Selecting Base Station Antenna
Or aerial, system of wires or other Conductors used to transmit or receive Radio or other Electromagnetic Waves (see Television). In a transmitting antenna, the signal from an Electric Circuit causes Electrons in the antenna to oscillate; these moving electric Charges generate Electromagnetic Radiation, which is then transmitted through space. The distribution pattern of the
transmitted wave depends on the design of the antenna; radio broadcast-station
antennas are frequently designed to emit waves in all directions, whereas those
used for Radar and for certain Communications systems focus the waves in a single direction. In a receiving antenna,
electromagnetic waves cause the electrons in the antenna to oscillate, inducing (see Induction) a signal that can be detected by an electric circuit. In general, a longer
antenna is used to transmit or receive signals of longer Wavelengths. Theoretically, the same antenna can be used both for sending and for
receiving signals, but in practice, transmitting antennas are constructed to handle
higher Power loads than receiving antennas. Phased array antennas, used for long-range
radar and Radio Astronomy, are composed of large groupings of individual antennas that are aimed
electronically by changing the relative phase of the signal at each antenna.