Transmitter

Radio transmitters on a tower.

In electronics, a transmitter is a device which sends signals using radio waves.

The transmitter converts direct current (DC) into alternating current (AC) at the desired frequency. Most transmitters use a quartz crystal to set the frequency of the resulting carrier wave. A modulator modifies the carrier wave, by frequency modulation or amplitude modulation or some other kind, to include the information needed, such as an audio or video signal. The modified waves are sent by an antenna to another antenna at the receiver which extracts the information from the waves.

Transmitter Media

Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, US. It broadcasts at 101.9 MHz with a radiated power of 48 kW.
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.
Hertz discovering radio waves in 1887 with his first primitive radio transmitter (background).
Guglielmo Marconi's spark gap transmitter, with which he performed the first experiments in practical Morse code radiotelegraphy communication in 1895–1897
High power spark gap radiotelegraphy transmitter in Australia around 1910.
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
An Alexanderson alternator, a huge rotating machine used as a radio transmitter at very low frequency from about 1910 until World War 2
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.
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.

Related pages

Other websites

This short article about technology can be made longer. You can help Wikipedia by adding to it.