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(NB This text is an extract from the late Harry Cole's unpublished work "The History of the Marconi Radar Company" 1997.)

The S600 series of radars was an unqualified success. This success resulted from applying classical marketing principles, notoriously difficult to do in the high cost capital goods field; predicting what the market wants and planning to produce it at a price users are prepared to pay means long-term commitment of massive resources — if you get it wrong, the results can be ruinous. It had been judged that the S600 series would become obsolescent by the late '70s and that the market need would be different. It was argued that the requirement for larger and more expensive systems was being satisfied in the UK by 'LINESMAN', in NATO by NADGE, in Saudi Arabia by SAGEU — in all of which Marconi was a major player. In the US these needs were satisfied by their own indigenous products, almost impossible to dislodge. However, the need persisted for the performance of the big static radars to be achieved by a mobile system. At the same time, electronic warfare was increasingly significant and resistance to 'jamming' was also vital. Air Defence radars have to provide height data on non-cooperative targets, thus to meet the needs the new radar must, perforce, be 3D.

The prototype STAR system had been tried out, using an S600 radar as an illuminator with a STAR vertical array to provide the necessary height data by within-beam scanning in the vertical plane. This was found to be much too expensive in bandwidth and money to give a marketable product. However, the technique could be adapted to provide a set of beams, overlapping in elevation. Each beam would have its own receiver and because the beams would be present simultaneously, monopulse technique could be used to get height data on targets from a knowledge of elevation and range. The beams would be formed by combining the receiver outputs at IF. By governing the precise phase and amplitude of these IF outputs and combining them in a passive beam-forming network, the individual beam's elevation angle could be accurately fixed. For target illumination the beams would effectively be combined to form one 'cosecant squared' pattern during transmission. It was decided that the Company would make a massive investment in a new family of 3-D radars using this systems architecture, with the family name 'Martello'.

The early work had already begun in 1973; a programme of definition for development having been mapped out. This was under the project name of “RAMPART”. At the time NATO had only an outline specification but it included restricting the operating frequency to the S-band (10cmj. It became clear that the range requirement called for exorbitant output power, extremely difficult to achieve; an L-band solution would clearly be preferable.

The UK MoD had expressed the view that the frequency band ought not to be specified in order to give manufacturers the greatest freedom to offer a wider variety of systems. In 1974 NATO deleted its preference for S-band, but their specification was still incomplete; there was still dissent among the NATO host countries on details of the specification. In the light of this, the Company took a chance and started a major development programme on an L-band solution expressly aimed at the NATO draft specification. Thus, the S713 began its life as father of the Martello family.

Its antenna was a planar array consisting of a vertical stack of identical linear radiators, each 6m wide and centre fed. There were sixty of these mounted on a central spine on a rotating pedestal. The vertical stack was 10.6m high. The array formed eight beams in the vertical plane. When in transmit mode, their combined pattern was used to radiate power provided by a coherent wide-band Twystron; pulse compression was used to enhance clutter rejection and resolution. The antenna was raised or lowered by a hydraulically-powered set of rams, the whole being transported on a long trailer chassis. A subsidiary trailer fitted with a twenty foot ISO container carried the radar head electronics including a two-position radar management display suite.

Martello was first exhibited at the Farnborough Air Show in 1978, creating a great deal of interest. Soon after came an order from the UK MoD for four systems and, not long after that, the Company was awarded the Queen's Award to Industry for Technology.

Up to the time Martello was produced there had been no substantial changes to the NATO specification. However, there had been considerable debate between the Service and Technical Groups of host countries. By the end of 1978 it became apparent that the NATO and UK definition of height accuracy determination was being relaxed, while that of target discrimination was being tightened. These changes were taking the NATO specification out of Martello's reach.

The implications were that the whole antenna, receivers, and beam-forming network would need complete redesign. It was realised that semiconductor technology had reached a point where an all-solid-state distributed transmitter system could be a viable reality. The difficult decision to begin a re-design of the S713 was immediately taken. The same system architecture was retained with one significant difference — the transmitter was now no longer a single entity; it was provided by giving each of the linear array boards its own transistorised L-band power unit as well as its own receiver. The antenna was also re-designed and now consisted of a vertical stack of forty identical linear arrays, giving a height of 7.1m. A narrower azimuth beam was formed by increasing the antenna width to 12.2m The spine carrying the linear arrays was also completely different; it now contained all the electronics for the transmitters and receivers, beam-forming network, drive circuits and power supplies. The S723 formed its surveillance cover by synthesizing all eight beams. As in the S713, all beams used pulse compression and digital signal processing, the targets being plot extracted and their height given by monopulse processing. Fortunately costs were kept down because full anti­-clutter processing was only required on the two lowest elevation beams. It was first seen in public at the 1984 Farnborough Air Show. It was a real triumph of mechanical and electronic engineering. Its virtues were quick to be appreciated by the RAF who purchased four systems. These were accepted into full service in 1989. Martello became the Company's flagship radar.

Input by John Brown

in the late 60s, I attended one of Dr Straker's future product policy meetings, and in a somewhat dramatic style, Nigel Ellis-Robinson, tabled a new Baddow ITM (Internal Technical Memorandum) entitled 'An Agile Beam Radar'.  At the time, E-R said there were no semi-conductor devices on the market to switch fast enough, but the concept was there.  Some years later Martello emerged, and now I was introducing it through my responsibilities for implementing IUKADGE in the UK, and at the Faroes!

Editors note - there were continuing developments up to the S743, S753 and S763 - see here

Martello

Wikipedia

Martello Type S713 (RAF Type 90) and Type S723 (RAF Type 91)

Martello Type 743

Flight Global article 1, 2

Radar tutorial - 723  743

This is from a 1988 RAF recruitment leaflet - shows actual use.

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