According to various internet sources, by 1939, radar had evolved to the point where is was practicable to use it in combat. The British had given a great deal of thought as to how radar could be used effectively, and this research proved extremely valuable during the Battle of Britain.   Meanwhile, the Americans were pursuing their own, independent, research into radar.  From 1930 to 1940, the U.S. Naval Research Laboratory explored the use of radio for ranging and detection, and in 1935, the Committee on Naval Appropriations of the U.S. House of Representatives provided $100,000 to the Naval Research Laboratory for the development of radar. The research led to the first U.S. radar, the XAF, which was permanently installed on USS New York (BB-34) in 1939. By the time the Japanese attacked Pearl Harbor on 7 December 1941, 20 radar units had been installed on selected ships.*   In production, the XAF was designated as the CXAM radar.   The follow up was the CXAM-1, which included some enhancements. 

SK was an improvement on the CXAM air search radar set. It was essentially an SC-2 radar set, with a larger antenna with 6×6 dipoles. The radar was capable of detecting a medium bomber at 10?000 feet and 100 nautical miles. There was no elevation control but elevation could be estimated roughly from positions of maximum, and minimum signal strength of the difference of the signals between the antenna rows. A later version was named SK-2 and used a large parabolic antenna fed by a dipole.+

Both the SK and the SK-2 were mainly used on larger units of the US Fleet.

*Partially sourced from Naval Heritage and History Command website.
+Partially sourced from the radartutorial.eu website.

There is one SK-2 radar dish included.   The detail and fineness of the radar is, frankly, incredible.   The bracing for the radar is well defined, while the mesh of the radar screen is as fine as photo-etch.  The base to attach the radar to the mast is also printed integral to the part.  The two biggest concerns one will have using this radar is a)  painting with a light enough hand that you don't clog the mesh, and b) getting if off the print raft without breaking it.

 This is Black Cat Models set AC3500091f, US Navy SK-2 radar (x1).  It retails for about $10.00 USD, and is available directly from Black Cat Models - who I'd like to thank for this review sample - or from some of our other fine sponsors.   Highly recommended!