RX12874

Winkle used a network of stations to listen for carcinotron broadcasts, and combined the information from them to track the jammer aircraft as effectively as a radar could.

The system was based on a series of High Speed Aerial (HSA) installations and AMES Type 85 ("Blue Yeoman") radars.

Once the location was determined, it was manually input into the interception controller's displays as if it were a normal radar return, distinguished only by its small circle icon instead of a single dot.

Operators could decrease the Type 85 receiver sensitivity while the radar passed that location, so that the jamming did not obscure the display at nearby angles.

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

[3] The Type 80 was a key part of the ROTOR system, a comprehensive radar and control network covering the entire British Isles.

The Royal Aircraft Establishment (RAE) immediately began developing their own carcinotrons for the V Bomber force under the name Indigo Bracket, while solutions to the jamming problem for the RAF's radars were studied.

Through the use of twelve 4.5 MW klystron transmitters broadcast through an enormous 75 by 50 foot (23 by 15 m) antenna system, the Blue Riband produced 11.4 W per MHz of reflected signal at 200 miles (320 km), thereby overpowering the assumed threat.

To force the jammer to spread out its signal across a wide band, the radar randomly changed frequencies with every pulse, across a 500 MHz bandwidth.

[7] In keeping with this role, over the next few years the number of radar stations and fighters continued to be reduced as the protected area contracted around the Midlands.

Such jamming would require the launch of the V-force while the nature of the threat was determined, and repeated spoofing of this sort could quickly wear out the aircraft and their crews.

[11] Over time these plans were repeatedly scaled back, eventually producing a system known as Linesman with three stations covering only the southern portions of England, protecting Bomber Command's bases and the BMEWS radar.

[12] In 1947, the Royal Aircraft Establishment (RAE) was handed the task of developing guided missiles, taking over from a previously diverse group of efforts.

Among the group was George Clarke, who had worked on the LOPGAP missile guidance system but was more interested in advanced radar development.

This avoided a problem seen in densely trafficked areas where the interrogation pulse from the ground IFF transceiver would generate so many transponder replies that they would overlap in time and interfere with each other.

Instead, the signal would be received by three antennas, and using a device known as a "correlator", better known today as a matched filter, pulses from a single IFF broadcast could be picked out of the many possible returns.

By making similar measurements between all the stations, A-B, B-C and C-A, three such hyperbolas are constructed, which theoretically intersect at a single point, but more typically form a small triangle due to inherent inaccuracies.

Due to short flight times, a missile tracking system would want to detect the target as rapidly as possible, but as radars of the era were mechanically rotated, there was a limit to their scanning rate.

[13] Clarke proposed using a single large "floodlight" transmitter and three receivers placed at the corners of a 15 miles (24 km) baseline triangle.

A review of the concept suggested there were too many unknown factors to begin serious development, and Clarke was moved to a group working on radar countermeasures.

A design study for a system as part of the new radar deployment known as Plan Ahead, which later became Linesman, began in late 1958, followed by a development contract in August 1959.

This presented a problem; the correlator took a short time to perform its work, longer than the ideal scanning rate during the angle measurement.

The first High Speed Aerial was built at Marconi's factory in Bushy Hill and connected to the prototype Blue Yeoman at the RRE in Great Malvern.

After considerable testing and some minor corrections, the Staxton Wold site passed its acceptance trials in May/June 1968, and was handed to the RAF in October.

When Linesman was designed in the late 1950s, it was assumed that any war would quickly turn nuclear, and if H-bombs were going off there was no point in trying to prevent L1's destruction.

Since the Linesman system was designed primarily for early warning and anti-jamming during a short all-out nuclear war, it did not have the capability needed to deal with follow-up attacks.

Even before it reached its Phase 1 availability, it was decided to abandon further improvements to the system and use those funds to design and purchase its replacement as soon as possible.

During normal reception, a series of feed horns allowed signals from anywhere across the front of the antenna to be received in a pattern that was about 70 degrees wide.

The narrow beam of the Type 85 painted any single target for only about 1⁄50 of a second, and the HSA scanned the entire 70 degree space in front of it during that period.

The operator could control the gain to make the weaker spots disappear, and then estimate the location of the aircraft in the remaining set.