The rectangular frame-like object seemingly fastened above the pilothouse of the USS New York (BB-34) in 1938 wasn’t an oversized mattress spring or an early-model solar panel. It was the antenna for the XAF, the first radar set installed on board a major U.S. warship.
Successful tests of the new device—including three months of 20-hour-a-day operation for aircraft detection, navigation, and gunnery practice—convinced the Navy that radar would be a godsend. The awkward-looking, 17-foot-square antenna could reliably detect aircraft as far as 100 nautical miles out and spot surface ships 15 miles away. And it could track projectiles and falling shot while they were in flight.