Plain English Meaning

An older ADF instrument where you can turn the outer ring of numbers by hand. By turning the ring so your current heading sits at the top, the needle then shows the actual compass direction to the radio station, instead of just the angle from the nose of the aircraft.

Full Definition

An Automatic Direction Finder (ADF) instrument whose compass card (the circular dial showing 0°–360°) can be manually rotated by the pilot using a heading-set knob, so the aircraft's current magnetic heading can be aligned to the top of the dial. With the card set to heading, the needle then points to the magnetic bearing to the tuned non-directional beacon (), rather than only the .