Why does an AM radio channel require any bandwidth at all? Why can’t it just transmit on a single, precise frequency?
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I think most answers here just complicate things instead of getting to the root of the question.
>Why does an AM radio channel require any bandwidth at all?
The simple answer would be: because the information you’re trying to transmit (generally voice or music) is, even without modulation, a waveform made of a lot of different frequencies. For example, you need at least a bandwidth of 4 kHz (from around 20 Hz to 4000 Hz) for voice to be intelligible.
You can, in fact, transmit a SINGLE continuous tone using AM modulation. That would require essentially no bandwidth (at least, mathematically speaking it would be infinitesimal), but that transmission would be useless because the whole point of communications is to transmit a *random*, *varying* piece of information.
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