Radar, in principle, had been known since the mid-1930s, but it was a practical nightmare, requiring huge antennas to attain even satisfactory accuracy. The U.S. Navy asked AT&T Bell Labs for help in extending radar to higher frequencies, which would permit sharper beams and, thereby, smaller antennas. AT&T Bell Labs began its tests in 1939 , tracking ship movements from a hilltop along the coast of New Jersey. This resulted in the Mark 1, the first production high-frequency radar, which was installed on its first U.S. Navy warship in June, 1941. High-frequency radar, by the way, is a direct ancestor of the microwave oven.