large cylindrical parabolic reflector and 12 dipoles was used. This set was designated Type 285 and had a range of 15 miles. Types 282 and Type 285 were used with Bofors 40 mm guns. Type 283 and Type 284 were other 50-cm gunnery director systems. Type 289 was developed based upon Dutch pre-war radar technology and used a Yagi-antenna. With an improved RDF design it controlled Bofors 40 mm anti-aircraft guns (see Electric listening device). Microwave Warning/Fire Control The critical problem of submarine detection required RDF systems operating at higher frequencies than the existing sets because of a submarine's smaller physical size than most other vessels. When the first cavity magnetron was delivered to the TRE, a demonstration breadboard was built and demonstrated to the Admiralty. In early November 1940, a team from Portsmouth under S. E. A. Landale was set up to develop a 10-cm surface-warning set for shipboard use. In December, an experimental apparatus tracked a surfaced submarine at 13 miles range. At Portsmouth, the team continued development, fitting antennas behind cylindrical parabolas (called "cheese" antennas) to generate a narrow beam that maintained contact as the ship rolled. Designated Type 271 radar, the set was tested in March 1941, detecting the periscope of a submerged submarine at almost a mile. The set was deployed in August 1941, just 12 months after the first apparatus was demonstrated. On November 16, the first German submarine was sunk after being detected by a Type 271. The initial Type 271 primarily found service on smaller vessels. At ASE Witley, this set was modified to become Type 272 and Type 273 for larger vessels. Using larger reflectors, the Type 273 also effectively detected low-flying aircraft, with a range up to 30 miles. This was the first Royal Navy radar with a plan-position indicator. Further development led to the Type 277 radar, with almost 100 times the transmitter power. In addition to the microwave detection sets, Coales developed the Type 275 and Type 276 microwave fire-control sets. Magnetron refinements resulted in 3.2-cm (9.4-GHz) devices generating 25-kW peak power. These were used in the Type 262 fire-control radar and Type 268 target-indication and navigation radar. United States In 1922, A. Hoyt Taylor and Leo C. Young, then with the U.S. Navy Aircraft Radio Laboratory, noticed that a ship crossing the transmission path of a radio link produced a slow fading in and out of the