What is the purpose of COAC?

• A. Increases gain of IF stages
• B. Reduces the gain of selective IF amplifier stages for Large target returns
• C. Modulates the video signal
• D. Provides automatic gain control

Answer: (B)

COAC is a form of automatic gain control that specifically targets the IF path to prevent overload from very strong echoes. When a large target return comes in, the signal can push the IF amplifiers into non-linear operation or saturate the video, which blurs or hides weaker targets. COAC automatically reduces the gain in selected IF stages under these high-signal conditions, keeping the video output within a usable, linear range. This preserves the ability to detect weaker targets even in the presence of strong reflections. It’s not about simply increasing gain, and while it’s a type of AGC, its job is to attenuate gain for large returns rather than to boost gain or modulate the video signal.