![]() An alternating current flowing back and forth in an antenna will create an oscillating magnetic field around the conductor. Radio waves, electromagnetic waves of radio frequency, are generated by time-varying electric currents, consisting of electrons flowing through a metal conductor called an antenna which are changing their velocity and thus accelerating. This animation shows the action slowed enormouslyĮlectromagnetic waves are radiated by electric charges when they are accelerated. Loops of electric field (black lines) leave the antenna and travel away at the speed of light these are the radio waves. The voltage charges the two sides of the antenna alternately positive (+) and negative (−). The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). Main article: Radio transmitter design Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. 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. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers. The radio signal from the transmitter is applied to the antenna, which radiates the energy as radio waves. Many other types of modulation are also used. In a frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. In an amplitude modulation (AM) transmitter, the information is added to the radio signal by varying its amplitude. ![]() The information can be added to the carrier in several different ways, in different types of transmitters. It combines the carrier with the modulation signal, a process called modulation. The transmitter generates a radio frequency signal which when applied to the antenna produces the radio waves, called the carrier signal. The information is provided to the transmitter in the form of an electronic signal called the modulation signal, such as an audio (sound) signal from a microphone, a video (TV) signal from a video camera, or in wireless networking devices, a digital signal from a computer. The purpose of most transmitters is radio communication of information over a distance. The term transmitter is often abbreviated "XMTR" or "TX" in technical documents. A transmitter and a receiver combined in one unit is called a transceiver. This usage typically includes both the transmitter proper, the antenna, and often the building it is housed in.ĭescription 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.Ī transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. The term is popularly used more specifically to refer to a broadcast transmitter, a transmitter used in broadcasting, as in FM radio transmitter or television transmitter. Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters, even though they often have similar circuits. The term transmitter is usually limited to equipment that generates radio waves for communication purposes or radiolocation, such as radar and navigational transmitters. Transmitters are necessary component parts of all electronic devices that communicate by radio, such as radio and television broadcasting stations, cell phones, walkie-talkies, wireless computer networks, Bluetooth enabled devices, garage door openers, two-way radios in aircraft, ships, spacecraft, radar sets and navigational beacons. When excited by this alternating current, the antenna radiates radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. It broadcasts at 101.9 MHz with a radiated power of 48 kW. ( October 2022) ( Learn how and when to remove this template message)Ĭommercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it lacks sufficient corresponding inline citations.
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