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9-1: Basic Principles of Signal Reproduction
Selectivity: Q and Bandwidth
Selectivity in a receiver is obtained by using tuned circuits and/or filters.
LC tuned circuits provide initial selectivity.
Filters provide additional selectivity.
By controlling the Q of a resonant circuit, you can set the desired selectivity.
The optimum bandwidth is one that is wide enough to pass the signal and its sidebands but narrow enough to eliminate signals on adjacent frequencies.