..... Click the link for more information. ; radio radio, transmission or reception of electromagnetic radiation in the radio frequency range. The term is commonly applied also to the equipment used, especially to the radio receiver.
..... Click the link for more information. .
AM
in full amplitude modulationVariation of the amplitude of a carrier wave (commonly a radio wave) in correspondence to fluctuations in the audio or video signal being transmitted. AM is the oldest method of broadcasting radio programs. Commercial AM stations operate in the frequency range of 535 to 1605 kHz. Because radio waves of these frequencies are reflected back to the Earth's surface by the ionosphere, they can be detected by receivers hundreds of miles away. In addition to commercial radio broadcasting, AM is also employed in short-wave radio broadcasts, and in transmitting the video portion of television programs. See also FM.
Modulate a Carrier
Amplitude modulation (AM) is also widely used to alter a carrier wave to transmit data. For example, in AM radio, the voltage (amplitude) of a carrier with a fixed center frequency (the station's channel) is varied (modulated) by the analog audio signal.
AM is also used for digital data. In quadrature amplitude modulation (QAM), both amplitude and phase modulation are used to create different binary states for transmission (see QAM). AM is also used to modulate light waves in optical fibers. See modulation and carrier.
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| Vary the Amplitude |
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| In AM modulation, the voltage (amplitude) of the carrier is varied by the incoming signal. In this example, the modulating wave implies an analog signal. |
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| Digital Amplitude Shift Keying (ASK) |
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| For digital signals, amplitude shift keying (ASK) uses two voltage levels for 0 and 1 as in this example. |
amplitude modulation [′am·plə‚tüd ‚maj·ə′lā·shən]
| (communications) | Amplitude Modulation - (AM) A method of encoding data by varying
the amplitude of a constant frequency carrier. Contrast Frequency Modulation. |
Amplitude Modulation
a variation in the amplitude of oscillations (electrical, mechanical, and others) which takes place at a frequency much lower than the frequency of the oscillations themselves. Amplitude modulation is
used in radio technology—for example, in broadcasting. Sound vibrations are converted into electrical oscillations of low frequency Ω (the modulating signal) which periodically vary (modulate) the amplitude of the high frequency oscillations ω (the carrier frequency) generated by a radio transmitter (see Figure 1).
The amplitude-modulated oscillations are radiated in the form of radio waves that are intercepted by radio receivers, where the low frequency modulating oscillations are separated and converted back into an acoustic signal.
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