Adcock antenna (radio DF)

The Adcock antenna is a direction-finding array of spaced vertical elements, patented by Frank Adcock in 1909, used in marine and aeronautical radio direction finding to suppress the night effect that corrupts simple loop bearings. By using vertical monopoles instead of a horizontal loop, the array responds to the vertically polarized ground wave while rejecting the horizontally polarized component of downcoming sky wave, giving stabler bearings after dark. Adcock arrays were commonly paired with a Bellini-Tosi radiogoniometer so the operator could read the bearing without rotating the antennas. The technique underpinned shore HF/DF and shipboard RDF before GNSS.