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National Archives #19-N-30722
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FD Mark 4
| 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
| 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
Friedman
(1981)
Guerlac (1987)
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