Definition
A ground-based, low- or medium-frequency radio transmitter that broadcasts a signal equally in all directions. An aircraft equipped with an automatic direction finder (ADF) receiver uses the signal to determine the magnetic bearing from the aircraft to the station, allowing the pilot to home to, track from, or fix position relative to the beacon.
Plain English
A radio station on the ground that sends out a signal in every direction. A receiver in the aircraft points an arrow toward the station so the pilot knows which way it lies.
Context Anchor
Seen in instrument flying, older navigation procedures, and some approach charts that use an NDB as a point to navigate to or from.
Derivation
Nondirectional' means 'not pointing in any one direction.' The beacon itself does not aim its signal — it radiates outward equally on all sides. The direction information comes from the aircraft's receiver, not from the station.
Why Pilots Care
Supplies a simple backup navigation reference when other aids are unavailable or during certain instrument approaches.
Analogy
An NDB is like a radio station broadcasting in every direction. Your airplane’s receiver acts like a pointer that helps you tell which way the station is from you.
Intuition Check
Do not read nondirectional as meaning “useless for direction.” It means the ground transmitter sends the same signal outward in all directions; the aircraft receiver is what shows the direction to the station.
Example Sentence 1
After losing GPS signal, the pilot tuned the ADF to the local nondirectional beacon and tracked inbound to the airport.
Example Sentence 2
The chart showed the nondirectional beacon located five miles south of the airport.