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Standard AM is the modulation scheme used for wireless communication we most often consider AM radio. It is very similar to DSB-SC, but with an important change.

This form of amplitude modulation first adds a constant to the incoming signal, then multiplies it by a cosine signal (a sine wave, the math comes out nicer if you use cosine for it though the waves are effectively identical).

Or, in other symbols, given an input signal G(x), the output signal H(x) is (G(x)+A)*cos(f*t), where f is the frequency in radians.

This constant is chosen such that the absolute value of the input signal's variation from zero will never be greater than it.

This is done so that an incoherent demodulator, also known as an envelope detector can be used on the receiving end. What an envelope detector does, essentially, is take the absolute value of the incoming signal's amplitude. This is why it's possible to build a crystal radio, which is a very simple electronic device.

Compare DSB-SC, single sideband, and QAM.

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