Definition
A radio receiver equipped with a directional antenna used to determine the bearing from which a radio signal is being transmitted. Ground-based DF equipment is used by air traffic facilities to locate aircraft by tracking the direction of their radio transmissions, and can provide pilots with steering information back to the airport.
Plain English
A piece of radio equipment that tells you which direction a signal is coming from. On the ground, controllers can use it to figure out where an aircraft is by listening to its radio calls and seeing which way the signal is arriving from.
Context Anchor
Seen in radio navigation, older navigation equipment discussions, and some emergency or position-finding contexts.
Why Pilots Care
Enables a pilot or controller to obtain a bearing to a station or distress beacon for navigation or search-and-rescue.
Intuition Check
DF does not mean a general sense of direction or a visual pointer. Here it means equipment that finds direction by receiving a radio signal.
Example Sentence 1
The pilot, unsure of his position in deteriorating weather, contacted the tower and requested a DF steer back to the field.
Example Sentence 2
ATC used the direction finder to establish the position of the aircraft reporting an emergency.