12 Facts About Amplitude modulation


Amplitude modulation is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave.

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Single-sideband Amplitude modulation uses bandpass filters to eliminate one of the sidebands and possibly the carrier signal, which improves the ratio of message power to total transmission power, reduces power handling requirements of line repeaters, and permits better bandwidth utilization of the transmission medium.

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In electronics, telecommunications and mechanics, Amplitude modulation means varying some aspect of a continuous wave carrier signal with an information-bearing Amplitude modulation waveform, such as an audio signal which represents sound, or a video signal which represents images.

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However its presence provides a simple means of deAmplitude modulation using envelope detection, providing a frequency and phase reference to extract the Amplitude modulation from the sidebands.

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In some Amplitude modulation systems based on AM, a lower transmitter power is required through partial or total elimination of the carrier component, however receivers for these signals are more complex because they must provide a precise carrier frequency reference signal from a greatly reduced "pilot" carrier to use in the deAmplitude modulation process.

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Christmas Eve

Simple form of amplitude modulation is the transmission of speech signals from the traditional analog telephone set using a common battery local loop.

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Amplitude modulation was one of the first researchers to realize, from experiments like the above, that the existing technology for producing radio waves, the spark transmitter, was not usable for amplitude modulation, and that a new kind of transmitter, one that produced sinusoidal continuous waves, was needed.

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Amplitude modulation invented and helped develop one of the first continuous wave transmitters - the Alexanderson alternator, with which he made what is considered the first AM public entertainment broadcast on Christmas Eve, 1906.

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Amplitude modulation discovered the principle on which AM is based, heterodyning, and invented one of the first detectors able to rectify and receive AM, the electrolytic detector or "liquid baretter", in 1902.

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Amplitude modulation was virtually the only type used for radio broadcasting until FM broadcasting began after World War II.

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Amplitude modulation's analysis showed only one sideband was necessary to transmit the audio signal, and Carson patented single-sideband modulation on 1 December 1915.

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One can view the sidebands as that Amplitude modulation m having simply been shifted in frequency by fc as depicted at the bottom right of figure 2.

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