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FD Fire Control Radar
Photograph of director with FD radar
National Archives #19-N-30722
Cropped by author
FD Mark 4
Specifications:
Wavelength
40 cm
Pulse Width
1.5 microsecond
Pulse Repetition Frequency
1640 Hz
Power
15-20 kW
Range
12,000 yards (11,000m) on 5" (127mm) shell splash
40,000 yards (37,000 meters) on
bomber
12,000 yards (11,000 meters) on
submarine
20,000 yards (18,000 meters) on
destroyer
30,000 yards (27,000 meters) on
battleship
Scope
A scope
Accuracy
40 yards (37 meters)
4 mils
Resolution
1500 feet (460 meters)
10 degrees
Production:
667 sets from 1941 to 1944
FD Mark 12
Specifications:
Wavelength
33 cm
Pulse Width
1.2 microsecond
Pulse Repetition Frequency
480 Hz
Power
100-110 kW
Range
45,000 yards (41,000 meters) on
bomber
40,000 yards (37,000 meters) on
battleship
Scope
A scope
Accuracy
15 yards (14 meters)/3 mils
Resolution 300 feet/7degrees
Production: Used on Mark 37 directors for
5"/38 guns
starting in 1944
The U.S. FD fire control
radar was known in British
service as the Type
285. It was similar to FC
but had a larger antenna and gave altitude information. The antenna was
a stabilized 6' by 6'
(1.8m by 1.8m) double reflector with 2x4 dipoles and the display was an
"A" scope with a 100,000 yard (91,000 m) range scale.
An improved version, the Mark 12, used the same antenna but an
improved set. The Mark 12 also incorporated a Mark 22 low angle height
finding radar. Its "A" scope used a 50,000 yard (45,000 m) range scale.
References
Buderi
(1998)
Friedman
(1981)
Guerlac (1987)
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