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Mk. 12

Description of the radar set, tactical-technical characteristics

Figure 1: Mk. 12 (rectangle antenna)
and Mk. 22 (orange peel antenna)

Figure 1: Mk. 12 (rectangle antenna)
and Mk. 22 (orange peel antenna)

Specifications
frequency: 920 … 970 MHz
(UHF-Band)
pulse repetition time (PRT):
pulse repetition frequency (PRF): 480 Hz
pulsewidth (τ): 1 µs
receive time:
dead time:
peak power: 100 kW
average power: 48 W
instrumented range: 22 NM (≙ 42 km)
range resolution: 460 m
accuracy:
beamwidth: 10°
hits per scan:
antenna rotation:
MTBCF:
MTTR:

Mk. 12

Mk. 12 was operating in UHF-Band fire control radar. It was used with the gun director Mk. 37 with 5-inch guns. The radar had automatic tracking in range and measurement of range rate.

The antenna has two main cylindric parabolic reflectors one on top of the other. These reflectors are each 4 feet long by 2 feet high with a focal length of approximately 1/4 wavelength. Each reflector is fed by 8 dipoles mounted with their axes coincident in a horizontal line along the focal line of the reflector. The sixteen dipoles are electrically connected in four groups of four dipoles. These groups are connected to a lobe switch to position the beam in one of four positions.

Mounted centrally on the front of the antenna at the junction of the two parabolic reflectors is a smaller antenna consisting of a parabolic cylinder, 2 feet by 2 feet, fed by two dipoles. This antenna is used to suppress the side lobes of the main antenna.

Mk. 12 replaced the Mk. 4 radar but had the same limitations in low elevation angles. The radar was therefore connected with the additional Mk. 22 radar (the “orange peel” antenna in Figure 1).