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AM
AM is a type of radio wireless communications and stands for
"Amplitude Modulation".
| In order to transfer audio information - speech
or music - over radio waves we first need to convert the low frequency
audio into a higher frequency that can travel further and be picked up
by radios long distance. One means of doing that is AM radio.
In this case we simply pick a high frequency carrier that is much higher
than the audio, say 1 Mhz. This means that
the radio frequency is oscillating one million times per second.
That is much much faster than normal audio whose frequencies do not
exceed 20,000 times per second (20 KHz). |
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Amplitude Modulation |
How do we modulate this low frequency audio information onto the high
frequency carrier? For AM we vary the amplitude of that higher
frequency (the power level) at the same rate as the audio information.
At the receiving end, the radio indeed does receive the 1 MHz signal.
However, it is able to de-modulate the audio information from it by
noting the speed that the power level of the signal varies. When
the audio information is de-modulated and thus recovered from the
carrier, it can be amplified and sent to speakers.
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