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9-2: Superheterodyne Receivers
Automatic Gain Control
The amplitude of the RF signal at the antenna of a receiver can range from a fraction of a microvolt to thousands of microvolts; this wide signal range is known as the dynamic range.
Typically, receivers are designed with very high gain so that weak signals can be reliably received.
However, applying a very high-amplitude signal to a receiver causes the circuits to be overdriven, producing distortion and reducing intelligibility.
With AGC, the overall gain of the receiver is automatically adjusted depending on the input signal level.