In response, in 1958 a new design was built by combining the electronics from the Blue Riband with a smaller antenna originally developed as an upgrade for the Orange Yeoman radar.

By this time the entire Linesman concept had been called into question, as the radar sites and unhardened centralized command centre would be trivial to destroy even with conventional weapons.

A key part of the concept was a set of six Sector Control Centers where data from all of the radars would be sent to produce the Recognized Air Picture of the surrounding area.

[3] As ROTOR was just getting started, in 1951 the Telecommunications Research Establishment (TRE) began experimenting with new low-noise crystal detectors that improved reception by 10 dB, and new cavity magnetrons of roughly 1 MW power.

These Type 80 Mark III's led to many changes in the ROTOR layout as the centralized control rooms were removed and the entire battle from detection to interception was instead handled directly from the radar stations themselves.

[5] In 1950, engineers at the French company CSF (now part of Thales Group) introduced the carcinotron, a microwave-producing vacuum tube that could be rapidly tuned across a wide range of frequencies by changing a single input voltage.

The Admiralty Signals and Radar Establishment purchased one and fit it to a Handley Page Hastings named Catherine, testing it against the latest Type 80 late that year.

To solve this problem, Blue Riband proposed mounting four antennas in a square, meaning the entire sky would be scanned after it rotated 90 degrees.

[14] For the Blue Riband, they adopted a somewhat smaller version with a 100 foot (30 m) diameter with six bogies carrying a framework on top that acted like a flat turntable.

The goal of ROTOR was to limit damage to the UK while RAF Bomber Command was destroying the USSR's ability to launch additional attacks.

[21] Defensive systems against aircraft would only be needed for a short period while the USSR built up its missile fleet, and beyond the mid-1960s the only purpose of radar would be early warning.

[23] The UK approached the US in October 1957, initially offering a site in northern Scotland, but in February 1960 it was moved south to its eventual location at RAF Fylingdales in order to allow it to fall under the protective cover of the shrinking air-defence area.

[24] While all of this was taking place, the RRE North Site, the Army-oriented centre, had invested some effort into a new radar antenna to replace the rather complex lens system used on the AMES Type 82 "Orange Yeoman".

[26] Based on this ongoing work, in November 1958 the Air Ministry set the specifications for a production model and gave it the name AMES Type 85.

In 1960, the Canadian National Research Council published a report on using this design to filter out carcinotron signals, which, like the ignition noise, looked like very short pulses in any single frequency as it swept through the band.

This gave added reason to have a radar that could provide early warning with enough range even in strong jamming to give the missiles ample time to aim and fire.

The passive tracking system would extend this out, at least against the jammer-carrying aircraft, to cover all of England north to the Scottish highlands as well as the eastern half of Ireland.

[37] As it appeared the three-station network would be all that would ever be built, the layout was modified from a triangle to a line by moving the inland position at Bramcote to the existing coastal ROTOR station at Boulmer on the coast.

[28] Zuckerman went further, pointing out that the coverage during peacetime made the system an excellent way to track civilian aircraft as well, and suggested that Plan Ahead might form the basis for a shared military/civilian air traffic control network.

[40] Meanwhile, the recently formed National Air Traffic Control Service under Laurence Sinclair were planning an extensive network of their own based on the new Decca DASR-1 and Marconi S264 radars.

In December, each of the stakeholders gave presentations on their prosed systems and areas of overlap, and the Patch Committee was tasked with returning a complete report within six months, in May 1961.

[45] A final change was made by moving the prototype Type 84 at RAF Bawdsey originally planned for Saxa Vord to Bishops Court in Northern Ireland, which saved one DASR-1.

[48] By the end of 1962 the mount and turntable were largely complete, but the klystrons remained a problem and now there were delays in the radio equipment that would carry the data to the MCC.

However, by applying the new technique of pulse compression, the RRE system demonstrated a 13 dB improvement in rain conditions with no effect on overall detection capability.

By the late 1960s the Warsaw Pact had reached some level of parity in both tactical and strategic weapons, and the idea of any aggression on their part being met by a massive nuclear retaliation was no longer reasonable.

[55] It was also revealed that the communications links were carried via the rather visible BT Tower, only to be replaced by landline systems running in conduits outside the Soviet embassy.

[56] This retained the three Type 85 systems, while upgrading the stations at Saxa Vord, Buchan and Bishops Court to handle more traffic and provide more complete coverage.

Improvements in receiver electronics had also made radar systems significantly more sensitive, allowing them to detect weaker returns, and thus cover the same area using far less power.

[59] The original prototype at the RRE South Site was no longer actively needed for the Linesman effort as the Neatishead unit began installation.

With every pulse, the two active klystrons would generate a single preselected frequency within their 60 MHz range and then be mixed together and sent to all twelve feedhorns and produced the classic Cosec² distribution pattern.