Global InformationType 271 radar information
 Type 271 was the primary sub-hunting radar of HMCS Sackville. Its lighthouse-like radome can be seen above the bridge. | |
| Country of origin | UK |
|---|---|
| Manufacturer | Allen West and Co, Marconi |
| Designer | ASRE |
| Introduced | 1941 |
| Type | Sea-surface search, early warning |
| Frequency | 2950 ±50 MHz (S-band) |
| PRF | 500 pps |
| Beamwidth | 8.6º horizontal, 85º vertical |
| Pulsewidth | 1.5 μs |
| RPM | 2 rpm |
| Range | 1 to 11 NM (1.9–20.4 km) |
| Diameter | 28 in (0.71 m) |
| Azimuth | 220 to 360º |
| Precision | ~2º, 250 yards range |
| Power | 5 kW, 70 kW |
| Other Names | Type 272/3, CD Mk IV, V, VI, Chain Home Extra Low |
| Related | Type 277 radar, 276, 293 |
The Type 271 was a surface search radar used by the Royal Navy and allies during World War II. The first widely used naval microwave-frequency system, it was equipped with an antenna small enough to allow it to be mounted on small ships like corvettes and frigates, while its improved resolution over earlier radars allowed it to pick up a surfaced U-boat at around 3 miles (4.8 km) and its periscope alone at 900 yards (820 m).
The prototype, 271X, was fitted to HMS Orchis in March 1941 and declared operational in May. Small numbers became available during the year, with about thirty sets in operation by October. The design spawned two larger versions, Type 272 for destroyers and small cruisers, and Type 273 for larger cruisers and battleships. The 272 was not considered successful and not widely used. The 273 differed in having larger and more focused antennas, providing higher gain and thus longer range. This proved very successful and was widely used.
Improved versions, known alternately as Q models or Mark IV, were introduced in early 1943. These had a more powerful 70 kW magnetron for greater range and added a plan position indicator (PPI) display which eased the task of arranging interceptions. The near-simultaneous arrival of ASV Mark III radar, huff-duff, Type 271 and new breaks into the German's Naval Enigma codes swung the Battle of the Atlantic decidedly in favour of the Royal Navy. Later that year, the 273Q aboard HMS Duke of York found the German battleship Scharnhorst at night, leading to its destruction during the Battle of the North Cape.
By the late-war period, improved versions of all of these designs were introduced. Originally known as the Mark V models, in March 1943 these were renamed Type 277, 276 and 293. These new models were retrofitted as ships came in for servicing and were widespread by late 1944. Type 271Q models remained in service on a number of ships in the post-war period, generally passing out of service with the ships that carried them.