High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder introduced in World War II. High frequency refers to a radio band t
FH4 "Huff-duff" equipment on the museum ship HMS Belfast
"Super Duff" equipment on the museum ship HMS Belfast. The circular indicator provides a direct reading of the relative bearing from-which signals are received - red numerals for to port of the ship, green for to starboard
Adcock antenna
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The Adcock antenna is an antenna array consisting of four equidistant vertical elements which can be used to transmit or receive directional radio waves.
High-frequency direction finding
…the field and direction finding investigations. NPL had two devices used in these studies that would prove critical to the development of huff-duff, an Adcock antenna and a modern oscilloscope. The Adcock antenna is an arrangement of four monopole masts connected electrically to act as two virtual loop antennas…
Diagram from Adcock's 1919 patent, depicting a four-element monopole antenna array; active antenna segments are marked in red.
27-meter (90-foot) diagonal spacing Japanese Adcock direction finder installation for 2 MHz in Rabaul