Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.
A stack of "fishbone" and Yagi–Uda television antennas
Coaxial cable feedline emerging from a VHF ground plane antenna.
Schematic of a wave moving rightward down a lossless two-wire transmission line. Black dots represent electrons, and the arrows show the electric field.
A radio transmitter is usually part of a radio communication system which uses electromagnetic waves (radio waves) to transport information (in this case sound) over a distance.
Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods connected to a radio transmitter (not shown). The transmitter applies an alternating electric current to the rods, which charges them alternately positive (+) and negative (−). Loops of electric field leave the antenna and travel away at the speed of light; these are the radio waves. In this animation the action is shown slowed down enormously.
Complicated waveguide feed of a military radar
One of the most common types of transmission line, coaxial cable.
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.  This animation shows the action slowed enormously
Electronic symbol for an antenna
Variations on the schematic electronic symbol for a transmission line.
Hertz discovering radio waves in 1887 with his first primitive radio transmitter (background).
Antennas of the Atacama Large Millimeter/submillimeter Array.
Guglielmo Marconi's spark gap transmitter, with which he performed the first experiments in practical Morse code radiotelegraphy communication in 1895-1897
An automobile's whip antenna, a common example of an omnidirectional antenna.
A transmission line is drawn as two black wires. At a distance x into the line, there is current I(x) travelling through each wire, and there is a voltage difference V(x) between the wires. If the current and voltage come from a single wave (with no reflection), then V(x) / I(x) = Z0, where Z0 is the characteristic impedance of the line.
High power spark gap radiotelegraphy transmitter in Australia around 1910.
Half-wave dipole antenna
Standing waves on a transmission line with an open-circuit load (top), and a short-circuit load (bottom). Black dots represent electrons, and the arrows show the electric field.
1 MW US Navy Poulsen arc transmitter which generated continuous waves using an electric arc in a magnetic field, a technology used for a brief period from 1903 until vacuum tubes took over in the 20s
Diagram of the electric fields ( blue ) and magnetic fields ( red ) radiated by a dipole antenna ( black rods) during transmission.
A type of transmission line called a cage line, used for high power, low frequency applications. It functions similarly to a large coaxial cable. This example is the antenna feed line for a longwave radio transmitter in Poland, which operates at a frequency of 225 kHz and a power of 1200 kW.
An Alexanderson alternator, a huge rotating machine used as a radio transmitter at very low frequency from about 1910 until World War 2
Cell phone base station antennas
A simple example of stepped transmission line consisting of three segments.
One of the first vacuum tube AM radio transmitters, built by Lee De Forest in 1914. The early Audion (triode) tube is visible at right.
Standing waves on a half wave dipole driven at its resonant frequency. The waves are shown graphically by bars of color ( red for voltage, V and blue for current, I ) whose width is proportional to the amplitude of the quantity at that point on the antenna.
One of the BBC's first broadcast transmitters, early 1920s, London. The 4 triode tubes, connected in parallel to form an oscillator, each produced around 4 kilowatts with 12 thousand volts on their anodes.
Typical center-loaded mobile CB antenna with loading coil
Armstrong's first experimental FM broadcast transmitter W2XDG, in the Empire State Building, New York City, used for secret tests 1934–1935. It transmitted on 41 MHz at a power of 2 kW.
Polar plots of the horizontal cross sections of a (virtual) Yagi-Uda-antenna. Outline connects points with 3 dB field power compared to an ISO emitter.
Transmitter assembly of a 20 kW, 9.375 GHz air traffic control radar, 1947. The magnetron tube mounted between two magnets (right) produces microwaves which pass from the aperture (left) into a waveguide which conducts them to the dish antenna.
The wave reflected by earth can be considered as emitted by the image antenna.
The currents in an antenna appear as an image in opposite phase when reflected at grazing angles. This causes a phase reversal for waves emitted by a horizontally polarized antenna (center) but not for a vertically polarized antenna (left).
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In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna.

- Transmitter

In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver.

- Antenna (radio)

In a radio antenna, the feed line (feedline), or feeder, is the cable or other transmission line that connects the antenna with the radio transmitter or receiver.

- Feed line

Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas (they are then called feed lines or feeders), distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses.

- Transmission line

In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line.

- Transmitter

An antenna lead-in is the transmission line, or feed line, which connects the antenna to a transmitter or receiver.

- Antenna (radio)
Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.

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