Transmitter
1. Overview of Transmitters:
- A transmitter is a device used in radio communication systems to transport information over a distance using electromagnetic waves.
- It can be a separate piece of equipment or part of another electronic device, with a transceiver combining both functions.
- Transmitters generate radio frequency signals applied to antennas to produce radio waves for communication.
- Examples include AM and FM broadcast transmitters, amateur radio transceivers, CB radios, and consumer products like cellphones and wireless microphones.
2. Operation and Components of Transmitters:
- Transmitters radiate electromagnetic waves through accelerated electric charges.
- Radio waves are generated by time-varying electric currents flowing through antennas.
- Components include power supply circuits, oscillators for frequency control, modulation circuits for encoding information, amplifiers for power increase, and antennas for radiation.
- The transformation of electric power into radio frequency alternating current is key to transmitter operation.
3. Regulation and History of Transmitters:
- Governments regulate transmitters to prevent interference and ensure safety.
- Licensing is required for specific frequencies and power levels allocated by the International Telecommunication Union.
- Historical advancements include spark gap transmitters, vacuum tube technology enabling AM broadcasting, and the invention of FM transmission by Edwin Armstrong.
- Licensing requirements have evolved over time to include technical and legal knowledge for operators.
4. Modulation Methods and Technological Advancements:
- Various modulation methods like AM, FM, FSK, and OFDM are used in different transmitters.
- Modulator circuits add information to carrier waves, RF amplifiers increase signal power, and impedance matching circuits ensure efficient power transfer.
- Advancements include the transition from spark gap to vacuum tube transmitters, the invention of FM transmission, and the development of transistor technology for portable devices.
5. Notable Transmitter Examples and Related Topics:
- Examples include early BBC broadcast transmitters, Armstrong’s experimental FM transmitter, and air traffic control radar using magnetron tubes.
- Related topics cover transmission sites, radio transmitter design, repeaters for extended range, transposer devices for signal processing, and the role of television transmitters in broadcasting.
- Resources like books by Serway, Faughn, and Vuille, Steven W. Ellingson, and Marshall Brain provide insights into transmitter technology.
This article includes a list of general references, but it lacks sufficient corresponding inline citations. (October 2022) |
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.
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. The term transmitter is usually limited to equipment that generates radio waves for communication purposes; or radiolocation, such as radar and navigational transmitters. 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 is popularly used more specifically to refer to a broadcast transmitter, a transmitter used in broadcasting, as in FM radio transmitter or television transmitter. This usage typically includes both the transmitter proper, the antenna, and often the building it is housed in.
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