Which description corresponds to Automatic Direction Finder (ADF)?

• A. A GPS-based navigation aid.
• B. Electronic navigation equipment that operates in the low- and medium-frequency bands, used with NDB, showing the degrees clockwise from the nose of the aircraft to the station being received.
• C. An inertial navigation system.
• D. A VHF navigation beacon.

Answer: (B)

An Automatic Direction Finder uses signals from non-directional beacons (NDBs) that transmit on the low- and medium-frequency bands. The ADF receiver tunes to these LF/MF signals and the indicator shows the direction to the station as a bearing measured clockwise from the aircraft’s nose. This direct bearing to the beacon is the defining feature of an ADF, distinguishing it from other nav aids. The other options describe different systems: GPS-based navigation uses satellites, inertial navigation relies on internal motion sensors, and VHF navigation beacons (like VOR) operate on VHF and use a different type of bearing indication.