In an ADF system, which arrangement serves as the essential sense and loop components?

In an ADF system, which arrangement serves as the essential sense and loop components?

• A. VOR/ILS receiver
• B. Transponder antenna
• C. Localizer antenna
• D. Sense and loop antennas

Answer: (D)

In an ADF system, bearing to an NDB comes from two antennas working together: a loop antenna and a sense antenna. The loop antenna provides directional information but has a 180-degree ambiguity because its pattern is the same front and back. The sense antenna resolves that ambiguity by providing the front/back indication, so you get a true bearing to the beacon. Together, these two antennas form the essential pair for the ADF’s direction-finding function. Other components listed belong to different navigation systems: the VOR/ILS receiver is for VOR and ILS guidance, the transponder antenna is for aircraft identity and radar cooperation, and the localizer antenna is part of the ILS approach system. They don’t serve as the indispensable sense-and-loop pair used to determine ADF bearing.

In an ADF system, bearing to an NDB comes from two antennas working together: a loop antenna and a sense antenna. The loop antenna provides directional information but has a 180-degree ambiguity because its pattern is the same front and back. The sense antenna resolves that ambiguity by providing the front/back indication, so you get a true bearing to the beacon. Together, these two antennas form the essential pair for the ADF’s direction-finding function.

Other components listed belong to different navigation systems: the VOR/ILS receiver is for VOR and ILS guidance, the transponder antenna is for aircraft identity and radar cooperation, and the localizer antenna is part of the ILS approach system. They don’t serve as the indispensable sense-and-loop pair used to determine ADF bearing.