Definition
An electronic circuit in a radio receiver that automatically adjusts the receiver's amplification to keep the output signal at a relatively constant level, regardless of how strong or weak the incoming signal is.
Plain English
A built-in feature in a radio that automatically turns the volume up when the signal is weak and turns it down when the signal is strong, so what you hear stays at a steady level.
Context Anchor
Seen in discussions of aircraft communication radios, navigation receivers, and other avionics that receive signals.
Derivation
Gain in electronics means how much a circuit amplifies (increases) a signal. Automatic Gain Control simply means the circuit controls its own gain without the user having to adjust it.
Why Pilots Care
Prevents radio audio from fading out on weak signals or becoming distorted on strong ones, supporting reliable communications.
Analogy
It is like a device that quietly turns the volume up when a speaker is far away and turns it down when the speaker gets close, keeping the sound comfortable.
Intuition Check
Gain does not mean earning or winning something here. In this term, gain means electronic amplification: making a received signal stronger inside the equipment.
Example Sentence 1
Thanks to automatic gain control, transmissions from a tower five miles away and one fifty miles away come through the headset at about the same volume.
Example Sentence 2
Avionics technicians check the automatic gain control circuit when a navigation receiver shows inconsistent signal strength.