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thumb Crystal Palace transmitter, London
A transmitter is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications.
A transmitter usually has a power supplyAn electronic power supply often referred to somewhat incorrectly as an AC adaptor is an electronic device that produces direct current of a particular voltage and current from a source of electricity such as a battery or wall-socket power. The direct cur, an oscillatorAn electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. Types of electronic oscillator There are two main types of electronic oscillator: the harmonic oscillator and the relaxatio, a modulator, and amplifierAn amplifier is a device which changes a small movement into a larger movement. The relationship of the input to the output--usually expressed as a function of the input frequency--is called the transfer function of the amplifier, and the magnitude of thes for audioAudio can mean: sound that can be heard electronic or other signals of frequencies audible to humans (about 20--20,000 Hz) broadcasting or reception of sound high-fidelity sound reproduction sound recording and reproduction in general "I hear" in the Lati (AF), intermediate frequency (IF) and radio frequencyRF can also denote rheumatoid factor Radio frequency or RF refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. Such frequencies account for the following parts of (RF). Sometimes a device, for example, a cell phone contains both a transmitter and a radio receiver or transceiver. The modulator is the device which piggybacks (or modulates) the signal information onto the carrier frequency, which is then broadcast.
In broadcasting, the part which contains the oscillator, modulator, and sometimes audio processor, is called the exciter. Confusingly, the high-power amplifier which the exciter then feeds into is often called the "transmitter" by broadcast engineers. The final output is given as transmitter power output (TPO), although this is not what most stations are rated by.
Effective radiated power (ERP) is used when calculating station coverage, even for most non-broadcast stations. It is the TPO, minus any attenuation or radiated loss in the line to the antenna, multiplied by the gain ( magnification) which the antenna provides toward the horizon. This is important, because the electric utility bill for the transmitter would be enormous otherwise, as would the cost of a transmitter. For most large stations, the transmitter power is no more than 20% of the ERP. Electronics