Introduction

As part of the work for the ROTOR contract the decision was made to develop a fixed-coil design for the GCI stations. The engineering work on the fixed-coil display - Console Type 64 - and its radar office equipment was done at Great Baddow.

The fixed-coil display work was an important milestone, in that it established a display and data-handling laboratory that served Marconi for a quarter of a century and a pattern of engineering that led to products that were reliable and suitable for quantity manufacture. The fixed coil development started in 1950, aiming at completion in 1953. A large team of engineers, some graduates and some with practical Service experience, was set up and dedicated facilities for making prototypes were put in place. The development programme, like all large `crash' programmes breaking new ground, suffered a few problems. There were some difficulties with the tube, which was virtually being chosen by the Ministry, from alternatives that were in fact physically and dimensionally different, in parallel with the main development. None the less, production went ahead in a time scale that was appropriate for the whole project. The first 1000 or so  complete Type  64 consoles and several thousand items of radar office equipment were manufactured by subcontract in the Plessey Company as a result of a very close collaboration. Later, there was retrospective fitting to other stations such as the CEW, together with new stations, and these were produced in Chelmsford.

A British Success - The Console Type 64

by Wing Commander John M Brown OBE

In 1948, the worsening international situation led the Air Ministry to decide upon urgent action to bring back a number of radar stations into operational use.

In parallel with this action, Marconi's Wireless Telegraph Company Limited (MWT) was approached by the Ministry of Supply to undertake a study of the complete radar defence of this country and to make recommendations for its improvement. Such a request had never before been given to a commercial organisation, as, until then, this type of work had been the prerogative of the Government's Research Establishments.

The study was undertaken by Dr Eric Eastwood, Chief of MWT's Baddow Research Laboratories, who had formerly been on the Headquarters staff of No 60 Group during the war. He was assisted by a team of experts and they used Trimley Heath GCI Station for experimental purposes. The recommendations made in the Radar Defence Study covered the lines of future research including the design and development of transmitters of higher power, Moving Target Indication (MTI) for clutter reduction, and (of interest to us in this article) a completely new display system which would meet the needs of the Services for some years to come — Fixed Coil.

Development of the Console Type 64

Formerly, ppi radar displays had used rotating deflection coils around the neck of the CRT, connected to the radar head through an electro- mechanical link. Fixed coil, as its name implies, uses static deflection coils, but fed with suitable X and Y waveforms to produce the rotating trace on the tube face. This now facilitated the presentation of additional information and symbols such as identification markers, area maps, multiple head selection, sector sweeping, trace expansion, and inter-console marking. This latter facility enabled operators to work together and to allocate positively and pass plots from one another.

MWT embarked on the development of the fixed coil system in 1950. The concept was to keep the display console as compact as possible, to enable consoles to be grouped together, and to feed them from centralised back-up cabinets housed in the Radar Office. The ability to easily service the console involved the mounting of sub-chassis on sliding runners or being hinged. The design of the circuitry was very sophisticated to ensure that the radar display accuracy was of a high order. This was of great importance since passing rotating waveforms through deflection coils can introduce distortion which can vary in different sectors. The deflection waveform was also complex since it now included inter-trace markers, so named as they were inserted during the flyback and deadtime period between the main radar scans.

The design of the new 12" CRT was entrusted to the English Electric Valve Company, and, in service, it proved to be a superb display tube with extremely high resolution and excellent afterglow characteristics giving good track continuity. The advanced characteristics of the CRT necessitated comprehensive protection circuitry within the console to include trace dimming in the event of scan failure, and octagonal blanking to limit the excursion of the scanning beam towards the edges of the tube (to prevent tube puncturing).

On the initial version of the Console Type 64, the control desk included a knob from which a Type 13 nodding height-finder could be positioned and a 'slaved' azication inter-trace line marker would confirm its direction. Even allowing for the reduction in the physical size of the Console 64, compared with its predecessors, being valved, it required a good flow of cooling air, which, when installed at a radar station, was supplied from the centralised equipment cooling system.

The fixed coil display system was developed and produced in three years, an astonishing achievement bearing in mind its complexity. Its production was shared between MWT and Plessey; some 600 display consoles were produced, as well as all the back-up equipment. The first ROTOR GCI to be equipped was Bawdsey in December 1953, and up to ten stations were being worked on within the ROTOR plan at any one time. By the middle of 1955, ROTOR had been installed, but, subsequently, because of the success of the fixed coil system, the CEW ROTOR sites were re-built to take the Console 64 in place of the previously installed moving coil Console 60. The Console 64 System was also installed in France and Germany.

Signals Plan 1958 — ROTOR Phase 1A

The Radar Defence Study of 1948/49, referred to earlier, had foreseen the evolution of the fixed coil system, as well as the development of the new generation of higher powered surveillance radars, the Radar Type 80 being the first. This radar, through its excellent operational performance, reduced the necessity for the number of over-lapping ROTOR stations. Under the 1958 Signals Plan, a number of GCI stations were to be designated Master Radar Stations (MRSs) and, in 1956, MWT was tasked with re- designing the fixed coil system to exploit more fully the inter-trace capabilities.

This involved a major re-development of the back-up equipment and introduced a Dekatron 10:1 timing system, whereby the station prf of 250 was divided down to produce 10 inter-trace sequences. The opportunity was also taken to introduce automatic zero control circuitry to negate the need for setting up controls, whilst achieving optimum registration between the main radar trace and the individual inter-trace sequences. Changes were also made to the Console 64 to introduce a joystick to give position and velocity control to inter-trace markers, as well as the ability to `dial up' (using a GPO-type dial) an individual console and route a marker or symbol to the selected console. The additional inter-trace marker facilities enabled inter-station marking to be possible as well as the ability to transmit co-ordinates to ground-to-air missile sites.

Furthermore, with the addition of active and passive selective IFF equipment, the interrogation of selected aircraft (by laying a marker over a target) was now introduced.

Two further operational requirements arose: the first, for a 21" CRT horizontal font-type console and this became designated the 4476. This console was designed to take up to four joysticks, enabling four supervisors to monitor operations at any time. Apart from more powerful deflection drive amplifiers, it shared similar units as fitted in the Console 64. The second requirement was for a fixed coil height/range display system to replace the Console 61 in ROTOR. This had been a re-engineered version of the wartime DU6, but was unstable and was incompatible with ROTOR Phase 1A; additionally, the new height/range system needed to work with both the Radar T13 and the recently introduced American FPS-6. ROTOR Phase 1A system was introduced into the Services in 1959.

Raid Analysis Displays

With the added flexibility of the fixed coil system, under Phase 1A, MWT was tasked with the development of Type A and Type B scope presentations for raid analysis on the Console 64. In the case of the B-scope, a joystick controlled 'bucket' marker was placed enclosing a designated target (a gated area of 20 miles by 20°). On the B-scope display, the bucket sector appeared as a rectangle, with the individual targets shown as squares. A joystick-controlled marker on the B-scope display was then positioned to encircle the 'square response'.

On the A-scope, the responses were staggered (slightly displaced by introducing some azimuth scan into the range scan). An even more successful A-scope presentation was achieved by accident! Whilst working with a colleague at Baddow, who was buried under the console plinth re- connecting cables to the console, he, in error, reversed two cables which meant we had a range and azimuth scan reversal. It so happened, that just as I was switching on, the Section Chief walked in, looked at the Console and said, "It looks like a magic carpet". It did; the single range base line had now turned into a lozenge shape, and sprouting out of the `carpet' were the perfect spectrums of two targets. It combined the best features of the A and B scopes in one presentation. The ease of target analysis were self-evident. Thereafter, it was always known as 'Magic Carpet' and it was sold to several Air Forces overseas.

Conclusion

The Console 64 remained with the Royal Air Force for nearly 40 years; it started with ROTOR, continued with Linesman/Mediator, and was only removed with the introduction of the latest system: Improved UKADGE. The quality of the display picture of the Console 64 was a by-word in the Fighter Control Branch of the RAF; it was rarely bettered for sharpness and consistency. It pioneered the introduction of fixed coil, a system on which all future displays was based.

Photographs

(The coloured photographs are taken at the RAF Signals Museum, Henlow - click thumbnail for a larger version)

R3 Intercept Cabin	Indicator Unit
Console 64	Showing LH and RH Deflection Amps & Voltage Stabiliser

Extract from article by Roy Simons

In 1950 it was decided that the displays for the GCFs should be 'fixed coil’ which would enable markers to be displayed. These displays would use a 'new' fluoride CRT that would give better track presentation than the existing green or blue phosphor tubes. This decision resulted in a major development programme at Baddow to attempt to design and produce a new display with all its radar office equipment to meet the original time scale of the end of 1953 for completion of ROTOR 1. In fact all the CEW and CHEL sites were completed by April 1953. The first GCI at Bawdsey was ready in December 1953.

In order to implement the 'Fixed Coil' display work a large number of engineers were recruited to supplement the existing radar people. Many of these had wartime experience, but about an equal number were new graduates. Rooms 123a, 123b, 124, 101, 102, 103 at Baddow were made available. A special workshop team was allocated to ROTOR prototyping under Fred Leach and a complete radar office was erected with all its cooling plant in Room 123a and three displays in Room 103.

Maurice Cuffiin was initially the project manager for the radar office and I was the project manager for the display. Cufflin left after a short period to join EMI and I became responsible for all the equipment design and its transfer to Plessey in a new factory in Horns Road Ilford, to where the manufacture was subcontracted. 

It was proposed that a liaison visit should be made to ASE Witley as it was believed that they were designing a display system to work with the 984 and it was probable that it might have similar requirements to ours. As a result of a full day's visit, the only information we received was a drawing of a diode with nothing connected to either end and the surprising knowledge that ASE were using the EEV metal coned CRT in their work.  

There were many reasons why the delivery of the first 'fixed coil' system was later than the hopes of the Ministry. The basic idea came from TRE, where an experimental data handling system was being studied using electromechanical storage from Ericcson. This became known as ADIS and the prototype was installed in H Block, well before the Blue Yeoman was added.

Originally the deflection waveforms were to be resolved using sine-cosine, as this gave a DC reference from input to output and would allow any markers to be easily referenced in position. However no wire-based resolver was capable of giving the smoothness and accuracy required, not to mention problems with contact noise. In the event, the sine cosine resolvers were retained for the height finding azimuth resolvers to present a short intertrace azimuth mark on the displays and a decision was  taken to use a magslip resolver for the PPIs.

This decision required the design of accurate clamps for the intertrace periods and precise linear amplifiers. One or two issues had to be solved. Diodes had significant heater to cathode leakage, causing AC modulation of the clamped position. This was cured by having separate heater transformers. The rotating armature of the magslip generated an AC current, which was not earthed reliably via the ball races at each end, causing noise. This was solved by adding a brush to remove the unwanted noise signals. Capacitors with a large dielectric constant were shown to have storage in the dielectric, solved by using a mica dielectric where needed.

Uncertainty or incorrect decisions were taken by the Ministry on some items which caused significant delay. The new CRT, the CV429, was initially made with various bulb shapes by several firms. There were also several contracts all starting to use this tube: Orange Yeoman, 984, PAR and our Type 64. At the meeting which I attended, the decision as to which shape should be used was determined by the Ministry looking to the system which was closest to production. At that time PAR! This determined the shape, which was that supplied by EMI. We had been using tubes with the Cinema Television bulb shape. When the specification was finalised we had a major redesign to cope with a much bulkier glass envelope.

This was not the end of the tube story. Mullard, who were convinced that they would get the contract, had proceeded to go firm on their glass shape and went into production. They did get the contract, (you could have expected it to have gone to EMI as their tube had the chosen shape) but, no, it was awarded to Mullard. Unfortunately the Mullard bulb shape did not conform to the Ministry drawings and they were not prepared to alter their production tools. They sub-contracted the manufacture to Cinema Television, which firm the Ministry had excluded from their consideration as the process control at the Rotunda was so poor that there was cross contamination between phosphors, which gave a white or green flash in front of the orange fluoride which was or should be without any initial flash.

Another decision, which caused considerable delay, was the requirement to reduce the width of the display console by one inch after the design was well advanced and initial models had been built. Almost every unit had to be redesigned, wrapping some round the now larger tube housing and reducing accessibility considerably.

A by-product of the choice of the EMI tube was the effect on the focusing arrangements. We had carried out a detailed analysis of the path of the beam through long focus coils using specially made one inch CRT's which could have the screen positioned at any point within the coil and a very good performance coil was designed and built into the prototypes. However the EMI tube had a very long gun assembly which reached almost up to the join with the bulb. This caused us to have to change to a narrow gap coil as used in domestic TV to avoid interaction between the metal of the gun and the magnetic field of the focus coil.

Another problem arose when we first put live radar on to the display. With the fixed coil system, off-centering to the full range of the picture was easily available. However, with the clutter off centred into the neck of the tube there was sufficient energy in the beam to puncture the glass. This caused a late extra development and incorporation of an octagonal blanking unit to prevent this happening by restricting the video pedestal to the area of the tube face.

Console 64 at the RAF Signals Museum at Henlow

Henlow have some of the equipment formerly at RAF Locking - the museum website includes a description of the Console 64 fixed-coil display system and details of the refurbishment of a Console 64 and associated drive equipment. Also available are copies of the APs (Air Ministry Publications) for the Console 64 and fixed coil back-up. In addition there is a video of the heightfinder being azicated by a joystick provided by Colin Hinson. These are training notes.

Editors note - it seems likely that this equipment is that I had in my charge when I was an instructor at Locking.