Definition
The component of a radar system that transmits radio energy in a directed beam and receives the portion of that energy reflected back from objects in the beam's path. Its shape and movement (typically rotating or scanning) determine the area the radar can cover and the direction information the radar produces.
Plain English
The part of a radar that sends out the radio signal and listens for the echo bouncing back. Where the antenna is pointing is the direction the radar is currently looking.
Context Anchor
Seen in discussions of ground radar, airborne weather radar, and how radar equipment detects aircraft, weather, or other objects.
Derivation
From Latin antenna, originally meaning the yardarm of a sailing ship -- a long pole sticking out to catch the wind. The word was later borrowed to describe rods that catch radio waves. Radar comes from Radio Detection And Ranging. So a radar antenna is literally the 'pole' that sends and catches the radar's radio signals.
Why Pilots Care
It enables detection of other aircraft, weather, and obstacles, directly supporting collision avoidance and safe navigation decisions.
Intuition Check
Do not think of a radar antenna as only a simple radio aerial for voice communication. In radar, the antenna also directs the radar signal and receives the returning signal used to locate objects.
Example Sentence 1
The weather radar antenna sweeps left and right ahead of the aircraft, painting returns from precipitation onto the cockpit display.
Example Sentence 2
Ground controllers used the radar antenna to track the aircraft's position as it entered the terminal area.