Definition
An antenna designed to transmit or receive radio signals more strongly in one direction than in others. Its radiation pattern is shaped so that signal strength is concentrated along a preferred bearing, allowing the antenna to favor signals coming from (or going to) a specific direction while reducing sensitivity to signals from other directions.
Plain English
An antenna that 'points' — it sends or picks up radio signals best in one chosen direction, and weakly in others.
Context Anchor
Seen in aircraft radio, navigation, and ground-station equipment discussions where signal direction or signal strength matters.
Derivation
From 'direction' (Latin directio, meaning a straight course or aiming) plus 'antenna.' The name simply tells you what the antenna does: it works in a particular direction rather than equally all around.
Why Pilots Care
Provides stronger, more reliable signals for navigation and communication while reducing unwanted interference from other directions.
Analogy
Think of a flashlight versus a bare bulb. A bare bulb (non-directional antenna) lights the whole room evenly. A flashlight (directional antenna) sends most of its light one way, so it's much brighter in that direction and dim everywhere else.
Intuition Check
Do not assume a directional antenna automatically tells you the aircraft's direction. It means the antenna's signal is stronger in certain directions than in others.
Example Sentence 1
The ADF uses a directional antenna so the needle can point toward the selected NDB station.
Example Sentence 2
Maintenance replaced the omnidirectional antenna with a directional model to strengthen the signal on the primary comm radio.