Definition
A ground-based, low- or medium-frequency radio transmitter that broadcasts a continuous signal in all directions. Aircraft equipped with an Automatic Direction Finder (ADF) receiver use the signal to determine the bearing from the aircraft to the station, allowing the NDB to be used for en route navigation, approach guidance, or as a position fix.
Plain English
A radio station on the ground that sends out a steady signal in every direction. A receiver in the aircraft points to the station so the pilot knows which way it is.
Context Anchor
Seen in instrument procedure and en route navigation discussions, especially where a route or procedure is based on a ground radio station.
Derivation
Called 'non-directional' because the signal is sent out equally in all directions, unlike a VOR which sends out directional radials. The pilot's receiver — not the station — works out the direction.
Why Pilots Care
Provides a simple backup navigation method in remote areas or when primary systems are out.
Analogy
An NDB is like a radio lighthouse. It does not point at you personally; it simply sends out a signal, and your equipment helps you figure out where the signal is coming from.
Intuition Check
Non-directional does not mean the pilot gets no direction from it. It means the ground station broadcasts in all directions; the airplane’s equipment provides the direction information.
Example Sentence 1
The pilot tuned the ADF to the NDB frequency and tracked inbound to the station.
Example Sentence 2
They used the NDB as a fix while flying the published instrument approach.