. The Bell System technical journal . similar in appearance tothe Main Unit of Radar Mark 1 shown in Fig. 9. Two types of antennas were provided for this radar: a 6 ft. by 6 ft.parabolic array similar to the Mark 1 antenna, and a 3 ft. by 12 ft. parabolicarray. Either one or the other of these antennas was mounted on top ofthe gun director and rotated with it in azimuth. Both were provided withazimuth lobe switching to be described later. Because of the relativelynarrow elevation beam of the 6 ft. by 6 ft. array, this antenna required gyro FIRE-CONTROL R.DARS FOR NAVAL VESSELS 23 stabilizatio

. The Bell System technical journal . similar in appearance tothe Main Unit of Radar Mark 1 shown in Fig. 9. Two types of antennas were provided for this radar: a 6 ft. by 6 ft.parabolic array similar to the Mark 1 antenna, and a 3 ft. by 12 ft. parabolicarray. Either one or the other of these antennas was mounted on top ofthe gun director and rotated with it in azimuth. Both were provided withazimuth lobe switching to be described later. Because of the relativelynarrow elevation beam of the 6 ft. by 6 ft. array, this antenna required gyro FIRE-CONTROL R.DARS FOR NAVAL VESSELS 23 stabilizatio Stock Photo
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. The Bell System technical journal . similar in appearance tothe Main Unit of Radar Mark 1 shown in Fig. 9. Two types of antennas were provided for this radar: a 6 ft. by 6 ft.parabolic array similar to the Mark 1 antenna, and a 3 ft. by 12 ft. parabolicarray. Either one or the other of these antennas was mounted on top ofthe gun director and rotated with it in azimuth. Both were provided withazimuth lobe switching to be described later. Because of the relativelynarrow elevation beam of the 6 ft. by 6 ft. array, this antenna required gyro FIRE-CONTROL R.DARS FOR NAVAL VESSELS 23 stabilization in elevation to take care of pitch and roll of the ship. Suchstabilization was not required with the broad elevation beam obtained withthe 3 ft. by 12 ft. antenna; and in addition, this wider antenna providedmore accurate tracking due to the narrower antenna beam in azimuth.Installations of these antennas aboard ship arc shown in Figs. 20 and 21and 22, 23 and 24.. Fig. 20—Radar Mark 3 antenna (6 x 6) on Cruiser Honolulu (Navy Photo 144-6-42) Antenna Lobe Switching The problem of measuring angles accurately with a relatively broadradio beam has been faced many times in the radio direction finding art.The most successful attack has made use of the fact that while the nose of aradio antenna beam is blunt, the sides of the beam are relatively steep; i.e., while the rate of change of signal amplitude with angle is very low near thenose of the beam it becomes substantial down on the side of the beam.A very well known application of this principle is the airway radio rangewherein two very broad overlapping beams define a narrow path by uti-lizing the points where the two overlap with equal intensity. A somewhatsimilar scheme in which the antenna beam is switched rapidly betweentwo positions has been applied in radar, and in an early form was first used 24 BELL SYSTEM TECHNICAL JOURNAL in this country by the Signal Corps in the work described by Gener

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