The introduction of the hydrogen bomb led to serious questions about the nature of the defence, as a single bomber escaping interception was capable of causing catastrophic damage.

In the area of air defence, they suggested moving the emphasis to research and development, as they expected there would be rapid technological improvement over the next few years and there was no point building existing designs that would soon be obsolete.

[8] ROTOR was to be a two-phase program, initially providing coverage only in the "Core Defended Area" around London, and then gradually expanding to cover the entire British Isles over time.

[17] Among the important advances in the immediate post-war era were higher-power cavity magnetrons over 1 MW, and the introduction of new wide-bandwidth low-noise crystal detectors.

[11] In 1950, the TRE combined these crystal detectors with new electronics and produced a microwave-frequency receiver that added 10 dB of signal-to-noise ratio, slightly more than three times the sensitivity of previous designs.

[23] An order for eight production units was delivered in July 1952,[c] with Decca building the electronics, Currans the turntable assembly, and Starkie Gardiner the 75 by 25 foot (22.9 m × 7.6 m) semi-parabolic reflector antenna.

[16] The design's improved resolution allowed it to distinguish between closely spaced targets at 95 nautical miles (176 km; 109 mi), well over twice the range of the Type 7.

Due to the curvature of the Earth, and assuming the maximum possible altitude of an air-breathing aircraft was about 60,000 feet (18,000 m), this corresponds to a range of 320 nautical miles (590 km; 370 mi).

[23] But Ardent also demonstrated that ROTOR's limited coverage over northern Scotland provided a "back door" route that allowed bombers to elude the fighters.

[24] Concerns expressed by the Admiralty that this route could be used to mine western ports led an order for an additional eight Stage IA radars in February 1953.

The only issue requiring modifications to the basic design was a minor change to the oil system in the 8 foot (2.4 m) diameter bearing that supported the antenna.

Trimingham was handed over operationally to the RAF in February 1955,[31] about six months later than initially expected, but still well over two years before the original ROTOR plans called for the MEW's to be installed.

[31] Several improvements were considered as the construction of the original units continued, including the addition of a new 2 MW magnetron and a pressurized waveguide system to keep humidity out of the piping to prevent arcing.

In January 1957, the installation at RAF Saxa Vord was subjected to 90 nautical miles (170 km; 100 mi) wind loads which strained the antenna, and demanded changes to the support framework and mounting system.

In the case of the Mark III, neither of these apply; the range of the system was so great that it could cover the entire inland area even if sited on the coast, and local reflections were avoided by the much narrower beam of the radar, which could aim away from obstructions.

In this case, a protracted battle might occur in which the RAF and Army would seek to attrite the Soviet force so that follow-up attacks would become ineffective, essentially a damage-mitigation strategy.

[43] In contrast to fission weapons, which had to be delivered relatively close to their targets, the hydrogen bomb was so powerful that it could be dropped within miles and still be effective, especially in a strategic role against cities.

With the accuracy demands greatly reduced there was no need for the bomber to fly over the target for aiming, one could drop the bomb from long range or use a booster to form a simple stand-off missile.

They had already given up on the concept of a close defence based on anti-aircraft guns and handed the SAM mission from the Army to the Air Force to be integrated into their interceptor operations.

IRBMs based in East Germany would hit the UK in about 15 minutes, potentially with no warning as the existing radar systems would not see them on their high trajectories far above the horizon.

If the Soviets flew aircraft far offshore and jammed the BMEWS radar, they could force the RAF to launch the V bombers to staging areas while the threat was investigated.

[53] In this case, even complete jamming of the Type 80 was acceptable, as it would still provide a warning that Soviet aircraft were aloft, without effecting the operation of the main stations far to the south.

[31] Ultimately only the logarithmic receiver was adopted, as it consisted solely of a small amount of additional electronics, while the polarizer required significantly more work and changes to the antenna.

It was originally designed for the British Army to sort and filter approaching aircraft and then hand off selected targets to the Yellow River radars that aimed the anti-aircraft artillery.

These stations were known as Air Traffic Control Radar Units (ATCRU), and organized around four major centres, Ulster (Killard Point), Southern (Sopley), Mersey (Hack Green) and Border.

The civilian air traffic control services paid for the installation of a digitizer ("plot and code extractor") to feed information from Bishops Court's displays into the overall ATC network.

[19][36] The technique of feeding high-power microwaves through slip rings was not fully developed when the Type 80 was being designed, so the radio frequency portions of the system are located in the "cabin" below the reflector, rotating with it.

A significant improvement in the Type 80 compared to earlier radars was an automatic tuning system that allowed it to easily adjust to changes in the frequency as the magnetron warmed and cooled, and especially when it was serviced or replaced.

Primary among these were the "fighter control cabins" that included a Console Type 64, which was centred on a 12 inches (300 mm) cathode ray tube display, which was a large format for the era.

This room contained the equipment that calculated altitude from the angle, passed messages between the various offices, ran the identification friend or foe system, produced map imagery that could be displayed on the consoles, and also in some cases received information from remote radars.