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A Note on Radar and ROTOR - 3 November, 1997

Page history last edited by Ian Gillis 8 years, 1 month ago

Roy Simons

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I am starting with the early days at Baddow, having given some detailed thought on this for use by the GEC Archives and also to fulfil a promise I gave to Bill Penley to let him have some information on the display development for ROTOR and go on from there. I will in general avoid the use of names, but there are one or two who will need to be mentioned, particularly Eastwood, without whom I doubt that MRSL would have existed.

 

The first real radar work done in Baddow was during the war, when magnetron production started in 1940, before being moved to Waterhouse Lane in 1942. However testing of production continued in an upstairs office at Baddow for a number of years, possibly until the end of the war, by just two people, Oldbury and Joan Swift.

 

Pre war. The curtain arrays for CH were a Marconi design.

 

Colchester's section. He had inherited the Telephone Lab. after the loss of Murphy, who went down in the City of Benares, designed antennas for naval use. Mostly Yagi types.

 

Lea's section had designed a range of crystal calibrators for radar ranging.

 

At least half of the Baddow site, (which was A Block plus a number of huts in the fields) was devoted to crystal manufacture. Jim Aikman was one of the first to take charge of this unit.

 

The other half of Baddow was the Ionospheric Bureau supported by Eckersley and R. J. Kemp's labs (originally TV Research) and many RAF and WRNS personnel.

 

The real origin of Baddow developing radar equipment started with a requirement by the Marine Company to enter the Marine radar market. As you will know the Marine Company did not have any development staff and had for years subcontracted its development to the Telegraph Company. The Marine development section of MWTCo was in New Street under James Watt, but they only knew about echo-sounders and radio, so the work was put into R. J. Kemp's section at Baddow who did not know anything about radar either, having spent all the war on DF systems and panoramic receivers with the associated CRT displays.

 

I can clearly remember R.J.K. coming into the lab. (Room 124) just after the end of the war and announcing 'We are going to do radar'. He knocked out his pipe as usual and left.

 

However the first design was based on the American Type 268 or to be more exact on the Canadian version Type 972, The first person who returned who had radar experience was Fred Garrett and he took the transmitter under his wing, whilst I designed the display from scratch using a deflection system similar to that in the 972, which originally involved the deflection waveform being passed out to the antenna and, having been resolved, back to the display. I changed this by introducing auto- alignment and selsyn tellback turning a three phase magslip resolver which was coupled to a magslip stator round the neck of the tube. This was Radiolocator I, fitted on the Duke of Lancaster or sometimes the Duke of Argyll sailing between Heysham and Belfast daily. The Duke of Argyll was involved in a collision which sank a large deep sea vessel in the dredged channel out of Belfast one night, when the captain decided to ignore the clear echo on the radar display which showed another ship stationary across the channel.

 

When Shipway returned (he had never been in development before, being previously a lecturer at Marconi College and during the war at Malvern), he brought with him knowledge of the very latest valve circuit techniques and when the Radiolocator II was designed this was all new, and was the basis of a profitable business by the Marine Company for many years. This was nothing like the Mk I and Baker's book is incorrect in this respect. Jimmy Watt's section took the Baddow design of the Mk II and. using the circuits, re-engineered it into possibly a more sea-worthy arrangement, with more aids to mariners incorporated, such as a simple form of movement correction based on the ship's log.

 

I sailed on the Duke of Argyll on its first sailing after it had had its bow replaced and with a new captain and the prototype Radiolocator II. There are a number of stories involving Shipway and Nightingale, which I am sure you must have heard. All relate to keeping your fingers off things you do not understand.

 

A by-product of Radiolocator II was the Jersey ACR. This used an early fluoride display tube and , had DF bearings superimposed.. The TX used a hydrogen thyratron instead of a spark gap and a much higher powered magnetron, the RX was both log and linear (designed by my wife Margaret) and the back to back antenna, high and low looking was new and fitted with removable circular polariser gates. The vertical linear feed was designed by John Rodgers. Unfortunately his first designs had the beam pointing at the ground; he forgot that the beam was formed towards the load! (A  copy of a picture of Baddow in 1947 or 48 showing the antenna on the roof is at Sandford Mill)

 

Immediately after the war, the Air Ministry had placed a contract with the Nelson Research Laboratories at Stafford under J. K. Brown to redesign the wartime Type 11 radar. They did not know anything about radar and this contact required them to work to the 'full procedure for government development', which meant four stages of development each separately approved and finished before the next stage was started. Although this was a procedure, which was doomed to failure, it was imposed on this contract and was attempted to be imposed on the subsequent contracts at Baddow.

 

However they did by sheer chance have two people who did know something about radar. The most important was Dr Eastwood. NRL did not have the resources to carry out their radar contract and the Air Ministry specified that the work should be transferred to Marconi. Why is not at all clear, as the Baddow knowledge of radar was, to say the least, slight.

 

As a result Eastwood, Blakemore, Worthy, Presland and a few others were moved to Baddow and a very long programme commenced before a new Type 11 came into existence. (E-R's paper is not quite correct on this subject). But of course, the knowledge that was gained with the use of 50cm. radar and clutter cancellation made a very useful contribution to other, mostly PV, radar systems.

Eastwood had many contacts in the Air Ministry and as a result MWTCo was asked to study the rebuilding of the wartime radar chain. This exercise became very urgent with the blockade of West Berlin in 1948 and the invasion of South Korea in June 1950. This study work was carried out by a team of engineers many of whom had joined Baddow after the war and most of whom had radar expertise. The wartime site at Trimley Heath near Ipswich was used for trials and the station W.O. George Slack joined the company as a result of his association at that time.

 

Contracts to improve the radars were awarded to the Company in August 1948 although the study report was not completed until mid-1949.

 

CRPC was set up in January 1950 with Walter Pretty as chairman, to monitor the progress of the work on the plan, ROTOR for the UK and VAST for overseas equipment.

 

Whilst the study was in progress, others at Baddow were engaged on further development of the Radiolocator for use on large Cunard liners and also on an Admiralty contract called POSTAL which was the research phase of the radar to be called the 984. The part of this latter work allocated to Kemp's section which was for a time run by B. J. Witt and shortly afterwards by Shipway was the transmitter monitor. This came out of our expertise in high-speed oscilloscope work. We had to design the oscilloscopes for testing the Radiolocator Mk II, as there was no suitable commercially available test gear. These 'scopes were the development and works standard for a number of years, including the period of the subsequent ROTOR display contract.

 

There were a number of visits to Witley to discuss the naval work. I remember a lengthy debate between the ASE people and Keall, who was designing the proposed receivers, over the measurement of noise figure to 0.1 dB. The real world was some way off at that time.

 

The initial ROTOR and VAST contracts (contractually in Services Equipment Division) were implemented by the newly formed RDG at Broomfield under Hugh Wassell. A great many new staff were recruited from people leaving the services and very substantial teams of development installation planning and installation people were assembled.

 

The contractual requirements were very large and it was not possible for all the development work, or all the production, to be carried out within MWTCo. Extra factories were opened and about 100 sub-contractors involved.

 

This first phase included improvements to the Types 7, 13, 14, both mobile and static, with the associated displays to be installed in CEW's CHEL's and GCI's. The PPI displays were rotating coil equipments (Console Type 60).

 

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.

 

One or two remarkable meetings took place during this period. On one occasion I was sacked, as were a number of other Marconi people, by Mr. A. G. Clark of Plessey, as we did not appear to be actually making something on the shop floor.

 

On another occasion, 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. Initially the participants were to be Shipway, Whitaker and Starksfield, but the Admiralty did not recognise the latter two, as they had never been cleared for naval work. In the event Eastwood Shipway and I went, as we were OK, and met Benjamin. 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 is an excellent photograph of Shipway, Whitaker and Starksfield and myself. The three of us were the management of the Datamation laboratories for a number of years, in fact until the re­organisation 1965)

 

Also at this time, RRDE were designing a display with markers, for use with Orange Yeoman. I visited Colin Fielding at Leigh Sinton Road and collected plenty of information, some of which had not reached St Andrew’s Road.

 

A momentous meeting took place in mid-1953 attended by Eastwood and myself. It was one of the regular series of progress meetings on ROTOR development and production, on this occasion chaired by Admiral Berghardt The secretary was Willie Bond and he recorded some of the comments verbatim, especially that made by Dr Eastwood who when asked to explain why the programme was late replied that 'He was a bl**** poor prophet.'

 

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 focussing 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.

 

During the course of the development I was asked by TRE to visit Kelvin Hughes, as they were having problems with their development of the photographic projector. I was interested to find that they had copies of our drawings (with my signature on them). The design was ours and 1 was surprised to find that TRE had not told us that they were giving out our design information to help another contractor.

 

I have to give enormous credit to Plessey for their mammoth efforts in getting the production line set up in such a short period. Dick Skinner and Alan Lescott were Production and Test Managers working for Parsons who had overall charge. There were many detailed changes and, with the speed of development, drawings and specifications overlapped production considerably. A final effort was their setting up a modification line in the Ops. Room at Bawdsey with a large number of Plessey operators to ensure everything that was offered for acceptance was up to the latest drawings and that on the day Mod State 1 could be stated as having been met.

 

Production progress meeting were held in the King's Head at Chigwell, where it was found that the MWTCo senior resident AID inspector, Brewin (his office was in Marconi House Strand) could be sent to sleep if he was provided with a suitable beverage at lunch. This allowed any contentious topics to be covered without too much debate and the AID inspector at Plessey, a certain D. Bell, (yes this is the one you remember) was on our side. The AID resident inspector in Chelmsford, Rose, was hardly ever seen during the course of this contract.

 

At the handover meeting, the Ministry of Supply who had been criticising the Company for being late, were embarrassed when the RAF refused to accept the station, as they were unable to man or maintain it for some months. It was handed back to the company until the RAF was ready.

 

Subsequent stations were built and handed over at a rate of one a month. The Company seconded Bruce Neale and the RAF seconded Alan Cushing (recently called up for National Service) as the setting-to-work team. They visited each station in turn and earned the respect of all concerned for their ability and understanding of every aspect of the system.

 

Ironically the size of the project with the number of stations, (62 by 1954), meant that other developments, such as Green Garlic (the prototype Type 80 radar) with much greater range than the Type 14, changed the performance requirement. ROTOR 2 which included the Type 80 radar saw the development of a 21 inch horizontal display. ROTOR 3 was for extra stations in Northern Ireland and the Western Isles. However the easing of international tension and therefore the possibility of hostilities reduced the need for the same number of operational stations. At the latter end of the programme, ROTOR stations were being handed over on one day and being dismantled the next.

 

The fixed coil display system stayed in service until LINESMAN became operational although in a progressively reduced number of stations. Operational facilities were added in Phase 1A and subsequently on a piecemeal basis, making greater use of the intertrace period. Joysticks were introduced to control markers and the heightfinders. Also there was a long-range modification, to allow displays to show returns to the full limit of the range determined by the PRF.

 

Over the following years, the Display and Data Handling labs at Baddow continued their work in extending the performance of systems with new technology as it became available. ROTOR was all valves, but by the end of the 1950's transistors were becoming available. This allowed the introduction of digital techniques. The first Ministry contract to use logic circuits was Passive Detection. On the display side, most of the circuits other than the output stages were able to be transitorised and equipments such as Labelled Plan displays and Tabular displays were produced and installed in West Drayton as part of the Middle Airspace System with three Myriad computers in the 1970's

 

Roy Simons

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Ian Gillis said

at 4:15 pm on Feb 10, 2016

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