They provided long-range early warning capabilities but also had the accuracy needed for interception plotting and "putting on" of other weapons systems like surface-to-air missiles.
Earlier mechanically scanned 3D radars used multiple feed horns in a vertical stack, but this was difficult to make in a mobile form; when moved they would go out of alignment.
The system was initially offered to the RAF, whose Linesman radar network was the subject of much concern over its survivability due to its fixed locations and single control centre in London.
Around the same time, NATO was beginning the process of upgrading their Europe-wide radar network, NADGE, and their basic requirements were similar to the UK's.
The key feature was mobility; the design had to be able to be pulled by Land Rovers, slung under a Sea King helicopter, and fit within a single C-130 Hercules aircraft.
This process produced several new requirements; like the S600, the system should be mobile or at least transportable, that it have improved jamming resistance, and that the era of the 2D radar and separate height finder used in the S600 was over and that the new design had to have a single 3D antenna.
The waveguide network and horns were complex and had to be accurately aligned during setup and maintenance, and a version robust enough to be mobile would be difficult to build.
A series of analog delay lines performed phase shifting on the IF to steer the beam electronically as well as store the resulting signal.
[11] Such a system can steer the beam vertically by delaying the signal as it is sent to the elements, and this phased array radar concept was being actively researched, especially in the United States.
The end result was a series of outputs, nine in the original design,[21] eight of which were aimed in a different vertical direction while the ninth was an all-sky beam used for early detection.
[20] The aimed outputs were identical to those created by the separate physical feed horns in a system like Orange Yeoman, but implemented completely in electronics in a box about the size of a minibar.
[22] Altitude information was extracted as it had been in Orange Yeoman; comparing a received pulse's strength in adjacent outputs allowed the vertical angle to be measured with some degree of accuracy.
[24] While development on new 3D systems continued, the Royal Air Force (RAF) was in the final stages of the installation of its latest radar network, Linesman.
Linesman had been designed in 1958, in the era when the NATO response to any attack by the Warsaw Pact would be widespread use of its overwhelming superiority in air power to deliver tactical nuclear weapons against high-value targets.
[25] By the late 1960s, the USSR was reaching some level of parity in both tactical and strategic weapons, and the idea that any war in Europe would be met by the early use of nuclear bombs was obsolete.
They repeatedly demanded that control of the interceptor aircraft take place at the radar stations rather than L1, ensuring that a single attack would not destroy the entire network.
[25][26] Other changes through this period including the new "plot extraction" systems that were highly effective at picking out moving aircraft, especially when they combined the information from more than one radar.
[28] Starting in 1972, the government redirected the money originally earmarked for upgrades to the Linesman system to be used to replace it as soon as possible with a new network known as UKADGE.
Chain Home had only survived attacks by the Luftwaffe due to the availability of backup radar systems that could be put into operation within hours, and Marconi noted their design could offer the same capability.
[18] At this point, Marconi had what appeared to be a sure contract win with the RAF but that would be a small number of radars; Linesman had only three main sites and two secondaries.
Feeling they still had a high chance of winning contracts for NADGE, Marconi took it upon themselves to develop a new version of the same basic system to meet the new requirements, the S723.
[34] During this period, semiconductor technology had been improving dramatically, especially in the high-power market where transistors were now available that were capable of controlling tens of kilowatts of power.
Marconi decided to modify the original design by replacing the single twystron with a series of individual transistorized transmitter modules, one on each horizontal row.
The main spar now carried all of the electronics and no longer required the separate transmitter semi-trailer, and all of the processing and display was reduced to a single ISO container.
The redesign also gave time to design packaging changes so the entire assembly now fit onto the antenna trailer and two 30 foot (9.1 m) ISO containers.
[38][40] Another was ordered using NATO funds for installation in the Faroe Islands and operated by the Royal Danish Air Force but feeding its data into the RAF's UKADGE system.
[41] Martello initially won only a single contract outside the UK under NADGE; the Royal Danish Air Force ordered an S723 which they sited on the island of Bornholm mounted on a tall tower.
[42][43][2] Part of the modernisation efforts of Hellenic Air Force's 2nd NARCS included the installation of the S-743D with the system entering service with the unit in May 1996.
This led to a further version with reduced stack height of only 16 elements, the LANZA-MRR (for Medium Range Radar), with the original retroactively becoming LANZA-LRR.
The MRR comes in two forms, one on a trailer that combines the entire system and can be set up and run as soon as power is supplied, and a similar version for use as a long-range naval radar.