Which navigation aid provides continuous display of the relative bearing of a received RF signal?

The Automatic Direction Finder (ADF) is the navigation aid that provides a continuous display of the relative bearing of a received radio frequency (RF) signal. It operates by receiving signals from non-directional beacons, such as NDBs (Non-Directional Beacons), and indicates the direction to the source of the signal relative to the aircraft's current heading. This capability is essential for pilots to navigate effectively, especially in poor visibility conditions, as it allows them to determine their heading toward the signal source and thus locate their position relative to navigational waypoints.

By continuously updating the relative bearing, the ADF aids the pilot in maintaining an accurate course towards the beacon. This real-time feedback is crucial in enabling effective navigation in both VFR (Visual Flight Rules) and IFR (Instrument Flight Rules) scenarios, contributing significantly to overall situational awareness.

Other navigation aids listed, such as VHF Navigation (ILS), Tactical Air Navigation System (TACAN), and Marker Beacon, serve different functions. The ILS is primarily used for precise approaches during landing, TACAN combines distance measuring capabilities with directional information but does not provide a continuous relative bearing in the same manner, and Marker Beacons are used to indicate specific points along a route rather than providing