Antenna (radio)
![](/Images/godic/202412/20/136_to_174_MHz_base_station_antennas2301.jpg")
![Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (−). Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves.](/Images/godic/202412/20/Dipole_xmting_antenna_animation_4_408x318x150ms2301.gif")
![Animated diagram of a half-wave dipole antenna receiving energy from a radio wave. The antenna consists of two metal rods connected to a receiver R. The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). Since the length of the antenna is one half the wavelength of the wave, the oscillating field induces standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R).](/Images/godic/202412/20/Dipole_receiving_antenna_animation_6_800x394x150ms2301.gif")
![Antennas of the Atacama Large Millimeter submillimeter Array.[11]](/Images/godic/202412/20/The_Atacama_Large_Millimeter_submillimeter_Array_(ALMA)_by_night_under_the_Magellanic_Clouds2301.jpg")
An antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.