World War II radar The yellow-green eye

By the beginning of World War II (1939), the German navy had developed a radar fire-control system1 that worked fairly efficiently, although its directional accuracy was still inadequate for night firing. Further effort was concentrated, in 1940, to overcome this deficiency. In England, the first radar sets employed wave-lengths of 11 to 12 meters, but continuous exreimentation with shorter wavelengths was pursued until the 9-cm wavelength became practical. English R & D was not confined to range-finding sets, but included images on a luminous screen oscilloscope (the ``yellow-green eye'') upon which all solid, moving objects near the receiver were outlined, together with their bearings and distances. German radar development lagged behind the British because it was concerned primarily with range-finding and not with all-weather reconnaissance capabilities. This month marks the 25th anniversary of the sinking of the Hood and the Bismuarek. SPECTRUM has been fortunate in obtaining first-hand technical and historical information on this significant chapter in the development of modern military electronics.