Keywords: blackandwhite monochrome outdoor cloud sky black and white NH 41639: 28 Megacycle Radar Antenna. Used by the U.S. Naval Research Laboratory (NRL) for detection of aircraft by beat method in 1930, and for radar (pulse technique) in 1936. Official U.S. Navy Photograph, from the collections of the Naval History and Heritage Command. NH 41639: 28 Megacycle Radar Antenna. Used by the U.S. Naval Research Laboratory (NRL) for detection of aircraft by beat method in 1930, and for radar (pulse technique) in 1936. Official U.S. Navy Photograph, from the collections of the Naval History and Heritage Command. |