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==== sidebands ====Any signal that is modulated produces sidebands. AM sidebands are predictable. FM sidebands are dependent upon the frequency deviation and modulation index. With an AM signal the bandwidth required is twice the maximum frequency of the modulation. While the same is true for a narrowband FM signal, the situation is not true for a wideband FM signal. Here the required bandwidth can be much larger, with detectable sidebands spreading out over large amounts of the frequency spectrum. Usually it is necessary to limit the bandwidth of a signal so that it does not unduly interfere with stations either side.