ASB Airborne Radar

Diagram of ASB airborne radar
Naval Historical Center


Wavelength 58.3 cm
Pulse Width 2 microseconds
Pulse Repetition Frequency     
400 Hz
Power 5-50 kW depending on model
Range 8 miles (13 km) for submarine
25 miles (40 km) for cruiser
60 miles (100 km) for coastline
Minimum range 350 yards (320 m)
Two Yagi dipole arrays
Modified 5" J scope
10% in range
3 degrees in bearing
152 lbs
69 kg
26,000 from late 1942

ASB was an early airborne surface search radar developed for American carrier bombers and flying boats. A similar radar was adopted by the Army as the SCR-521. It was a general-purpose surface search radar capable of detecting coastlines for navigation or surface ships for scouting and attack, and it had Identification Friend or Foe capability.

The set used two Yagi dipole array antennas, one below each wing. Each antenna was individually turned to point in any direction from straight ahead to perpendicular to the line of flight, so that the pair of antennas could cover an arc of 180 degrees in front of the aircraft. The display scope was a split J scope, with each antenna displaying on its side of the scope. Operators could compare the size of the pips on opposite sides of the scope as a kind of lobe switching to improve bearing accuracy, although the display was far from ideal for this purpose.

Aircraft using this radar included the SBD, SO3C, TBF, SB2C, PBY, PBM, PB2Y, and PV. It became the most widely used airborne radar of the war.


Jucker (2002; accessed 2014-6-19)
McMahon (1989; accessed 2014-6-19)
"U.S. Radar" (1943-8-1; accessed 2014-6-19)

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