SK was an American-made air-search radar used during World War II by the United States Navy. Models included SK-1, SK-2 and SK-3.^[2]

SK was a long wave search set for large ships. It furnished range and bearing of surface vessels and aircraft, and it could be used for control of interception. The set had both "A" and PPI scopes, provisions for operating with remote PPIs and for IFF connections, and built-in BL and BI antennas.^[3]

With the antenna at 100 ft (30 m), SK could detect medium bombers at 1,000 ft (300 m) altitude at 100 miles (160 km). Range accuracy was ± 100 yards (91 m) and azimuth accuracy ± 3°. There was no elevation control, but elevation could be estimated roughly from positions of maximum and minimum signal strength.^[3]

Shipment for SK included spares, with tubes for 400 hours, and a separate generator if the ship's power is DC. SK was not air transportable.

SK had 10 components weighing approximately 5,000 lb (2,300 kg). The heaviest unit, at 2,400 lb (1,100 kg), was the antenna assembly. The antenna measured 15 ft (4.6 m) x 16 ft 9 in (5.11 m). It was mounted 100 ft (30 m) or more above water. The minimum operators required were one per shift. Primary power required was 3500 kilowatts, 115 volts, 60 Hz. The source of power is ship's power of 115 volts, 60 Hz.^[3]

During the later stages of World War II, a parabolic antenna called SK-2 replaced the SK-1.^[1]

• SK-1 aboard HMS Trumpeter
• SK-1 aboard USS Texas
• SK-1 aboard USS Wichita
• SK-2 aboard USS Alabama
• SK-2 aboard USS Macon
• SK-3 aboard USS Princeton

• List of radars
• Radar configurations and types
• Air-search radar