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.

The prototype Type 79X, which was fitted experimentally to the minesweeper HMS Saltburn in October 1936, used a 4 m wavelength that required the antennas to be strung between the ship's masts.

[4] In February 1940, John Randall and Harry Boot built a working cavity magnetron, which soon produced 1 kW of power at a wavelength of only 10 cm from a device about the size of a shoe box.

The Valve Laboratory led development of the tunable reflex klystron that provided the needed intermediate frequency signal for a superheterodyne receiver that operated at microwave frequencies, while the Telecommunications Research Establishment (TRE), the Air Ministry's research arm, introduced a silicon-tungsten crystal detector that generated the appropriate high-frequency signals for the reflex klystron.

This test demonstrated the new radar's ability to pick up targets even when they were very close to the horizon, something previous designs could not do due to reflections off the ground that the tightly focused microwave signal avoided.

Through the summer and autumn of 1940, a period after the Fall of France later called the First Happy Time by Germans, British losses in the North Atlantic rose to unsustainable levels.

[7] During this wide-ranging "Trade Protection Meeting", the call for "An efficient radar set for anti-submarine surface and air escorts must be developed" was approved by the Prime Minister and given the highest national priority.

The solution was to place the transmitter and the initial stages of the receiver on the back of the antennas in a metal box, reducing the wiring length to about 1 foot (0.30 m).

[13] The antenna was placed on a rotating platform that was manually turned around the vertical axis using a drive shaft that passed through the roof of the radar operator's cabin and ended in a steering wheel taken from an automobile.

[17] After the successful tests on Orchis, Eastney continued to produce the original order and increasingly liaised with Allen West on the production models.

[18] The Type 272 was also mounted to cruisers, but in this role a new problem was discovered; the blast from the main guns was strong enough that it tended to crack the perspex in the radome.

[19] In October 1941, Mediterranean Command asked for some solution to the problem of detecting Italian human torpedoes which were attacking ships in Gibraltar and Alexandria.

A modified version of the Type 273 was provided, removing the stabilization system (not needed on land) and further increasing the reflectors to 4.5 feet (1.4 m) which improved gain to 575.

The installation occurred in two stages: during one cleaning a new area on the ship was prepared for the radar, and on its next visit a completed unit was hoisted aboard by crane.

Previously they would have to carefully watch for "blips" in the display as they swung the antenna, and then rotate it back and forth in ever-smaller motions in order to determine the exact angle.

The resulting phase of the mixed output signal encoded the angle between the antenna and north, and was used to drive another synchro on the CRT's deflection plates.

[15] Development of microwave techniques continued at a rapid pace through 1941 and by the end of the year several significant improvements had progressed to production quality.

[22] The most surprising of all was the new "strapped" magnetron design, a seemingly minor modification that produced an enormous boost in performance, allowing a unit the same size of the original NT98 to reach efficiencies on the other of 40%, or even 50 to 60% when used with a new and more powerful magnet.

[24] In order to deploy the new magnetrons as quickly as possible, it was decided to retain the existing antenna installations and use the CV56 at 70 to 100 kW, ultimately settling at 70.

[28] The system's most famous action was during the Battle of the North Cape on 26 December 1943, when the 273Q on HMS Duke of York detected the German battleship Scharnhorst at a range of 45,500 yards (41.6 km), and tracked her continually from that point onward.

[30] This early detection, combined with accurate blind-fire ranging from the Type 284 radar, led to the Duke of York landing her very first salvo on Scharnhorst and putting her forward batteries out of action.

[33] The Commander-in-Chief Home Fleet praised the performance of the system: a) The surface warning provided by Type 273Q was entirely satisfactory, giving on PPI a clear picture of the situation throughout the engagement.

Blast from the ship's own broadsides so shook the office that some of the overhead supports for the panels were carried away, but the set remained functioning throughout the entire period.

[38] By the end of August, the testing team reported: Operationally NT271X was a great advance on previous sets in maximum range, discrimination, counting and accuracy.

A new version, Radar, Coast Defence, Number 1 Mark 5, mounted the now single antenna on a separate and much smaller trailer with the rest of the electronics in a non-rotating semi-trailer.

[39] To address these attacks, in December 1942 the RAF took over eleven of the CD units and renamed them the AMES Type 52, but much better known as Chain Home Extra Low.

The flat upper and lower surfaces of the cheese made this simple, and the metal plates protected the receiver from stray signals from the transmitter.

This used a single cathode ray tube (CRT) with the beam being pulled across the display left-to-right by a time base generator triggered by the transmission pulses.