SCR-720 Airborne Radar

Photograph of SCR-720 radar antenna

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Wavelength 10 cm
Pulse width
0.75 microseconds
Pulse repetition frequency     
1500 Hz
Scan rate
360 rpm (ranges below 100 miles)
100 rpm (at 100 mile setting)
3 kW
Range Bombers at 10,000 feet (3000  m): 10 miles (16 km)
Fighters at 17,000 feet (5200 m): 5 miles (8 km)
Minimum 250 feet (75m)
29" (74 cm) parabolic
5" (12.7cm) B scope
5" (12.7cm) C scope
3" (7.6 cm) B or C scope
3 degrees
412 lbs
187 kg
In production by 1944-5

The SCR-720 (AI Mark X in British service) was an air intercept radar for night fighters derived from the larger SCR-520. It was used in the P-61 Black Widow and was equipped for IFF (Identification Friend or Foe). The scope could be set for maximum ranges of 1, 10, 20 or 100 miles (1.6, 16, 32, or 160 km), which was rather optimistic on the high end. It could search a full 180° forward of the aircraft, and its altitude search settings were 0° to 0°, -5° to +5°, +5° to +20° and +20° to +50°. The multiple scopes and range select features gave the SCR-720 partial immunity to chaff.

An unconventional use for the radar was to cover the blind spot directly overhead suffered by conventional Navy radar, which could only reach to about 75 degrees above the horizon. For example, several Essex-class carriers were fitted with SCR-720 sets on their catwalks to cover the blind spot.


Friedman (1983)

Naval Historical Center (accessed 2008-6-20)

Price (2005)

Wildenberg (accessed 2011-5-6)

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