Radar at Happisburgh

By Trevor Stevens, 18 February 2003

If you want to see a long way out to sea, one good way is to choose a high cliff on a piece of land sticking out to sea. So it is with coastal radar.

There are of course many other considerations. There must be an electricity supply or you would need diesel generators: there should be somewhere for the crew to live: it should not interfere with the local golf course: it should not in any way detract from the grouse shooting (a problem further north).

Happisburgh was a good choice and for two other reasons. Firstly it was about half way between similar units at Dunwich in Suffolk and Ingoldmills in Lincolnshire, and secondly it was more or less on a line between Germany and the industrial midlands.

You leave Happisburgh by the coastal road towards Walcott and Bacton, past Blacksmith's Lane on your right. After passing White's Farm on the left a few yards further on is a clump of trees on the right with a field entrance and a pillbox. You have arrived at the site of the first of Happisburgh's two radars. Nothing is now to be seen except a blast wall.

A chain of radars was established in the mid 1930's, the most visible signs of which were 3 or 4 very high steel masts (360 feet) carrying the transmitter aerials. This was called Chain Home (CH). The nearest of these to Happisburgh were at West Beckham in North Norfolk, and at Stoke Holy Cross just south of Norwich. These were high powered and had the ability to detect aircraft at well over 100 miles, but suffered from the disadvantage that they could not see low flying aircraft. Just before the war, the research boffins at Bawdsey were asked for advice. The matter became more pressing when, after war was declared, German aircraft were laying mines from low flying aircraft in the harbours of the east coast and the Thames estuary.

It so happened that Bawdsey had developed a higher frequency radar for coastal defence. Invasion was a possibility, and the new set was designed to detect ships but could also see aircraft flying as low as 500 feet up to 25 miles away.

Typical Chain Home Low radar stationThe Air Ministry purchased twenty four of these units of which Happisburgh was one. They were modified slightly and formed the basis of a new chain called Chain Home Low (CHL). Happisburgh was built at the end of 1939 and was operational at the end of the year. The unit consisted of a number of wooden huts, two of which contained respectively the transmitter and receiver. These were surmounted by a wooden gantry carrying a turntable and an aerial system looking like a very large bedstead which could be turned by an operator in the hut below.

In operation, radar involves sending a short pulse of radio energy as a beam and, if it hits an aircraft or other object, measuring the time it takes for the reflected signal to be received back at the station. When it is remebered that radio waves travel at the speed of light (186,000 miles per second) a very sensitive clock is necessary to measure this time. A cathode ray tube was the answer (much like todays TV picture tube). A spot on the tube can be made to move with incredible speed and can be made to form a complete television picture.

Typically a radar transmitter sends out four hundred short pulses every second, and at the same time as each pulse a spot is made to move from left to right across the centre of a cathode ray tube. As this spot moves at four hundred times every second there is no flicker and the operator sees a steady line. the line is calibrated in miles and the received echo, if any, is superimposed on this line. Thus the operator has the range and, because he knows which way the aerial is pointing, the bearing to the target.

In the beginning this information was passed to the CH at West Beckham, but after a while it was found that this overloaded the system and arrangements were made for all plots to be sent to a filter room at Watnall near Nottingham.

Happisburgh was working 24 hours per day, 7 days a week on a three watch system. The CO was a Flight Sergeant, and the watches were all male airmen. A watch consisted of an NCO and four or five operators and one mechanic all living in civilian billets. One watch was with Miss Cargill at The Rookery, and another with Mrs Giles at the farmhouse next door to the Lighthouse public house. Others were scattered in Walcott and Bacton.

As was common in wartime, very rapid improvements were made to the technical equipment. During 1941 the aerial systems were combined, still with manual turning by an operator sitting in front of the receiver and also a Plan Position Indicator (PPI) was introduced. This display was on the face of a round cathode ray tube (CRT) with the spot forming a line between the centre and the outer edge. The line so formed rotated about the centre, and any echo formed a small sausage glow as the aerial and the line, called a trace, rotated in step with each other. A transparent plastic mask covered the face of the CRT The National Grid was drawn on this mask so that instead of reading a range and bearing, the operator could read off a map reference to Watnall.

During this time experiments were made with fighter aircraft, and it was not long before specialist officer controllers arrived at Happisburgh to control, day or night, aircraft mainly from Coltishall. During they day Spitfires could see the target if pointed in the right direction by the Happisburgh controller who could see friend and foe on his screen. At night the aircraft would be Beaufighters or Mosquitoes who had their own very short range radars on board. It was a bit of a cat and mouse situation and very exciting for the radar crew who could watch and hear everything that was going on. Incidentally, there used to be a telephone kiosk near the cross roads where the coast road to Walcott and the Stalham road meet. As a result of crossed wires it was possible to listen to the radio telephone conversations between the ground radar and aircraft. Alas the kiosk is no more.

Life on duty at Happisburgh was either very boring in bad weather or very exciting in good, but things were to change in 1942. Firstly a group of WAAFs arrived to take the place of the male RAF operators who were posted elsewhere (probably overseas). They were billeted in Pyghtle, a house near the school in Happisburgh. As more girls arrived, Pyghtle was closed as a billet and they were all moved to Norton House in Bacton. Before long there were WAAF cooks, drivers, admin staff, admin officers and even radar mechanics.

The other thing of note brought Happisburgh right up to date with the construction of a new radar about 100 yards from the original unit and closer to the sea. For all the girl crews it was accessed by footpath from Happisburgh One, but the heavy equipment came in by track through Chimney Farm. The low brick building with flat concrete roof is still visible although the internal partitions have been removed together with all the equipment, and it is now used as a store for agricultural purposes. If you look very carefully at the bushes next to the operations block, it is just possible to make out the four concrete blocks which formed the feet at the base of a 185ft wooden tower. This had a motor driven revolving aerial on top which enabled the radar to see further and lower out to sea.

Happisburgh Two, being the more modern of the two units, plotted to Watnall the comings and goings of friendly and foreign aircraft and a few ships which were plotted to Yarmouth. A centimetre height finder was added in 1943. the unit was still operational in 1947 but it is not known when it was closed and the equipment withdrawn.

Happisburgh One on the other hand had no work to do after 1945 and indeed was running down before the end of the war. Many of the girls went away on cookery and other courses to prepare them for civilian life.

If you have been interested in radar at Happisburgh, it is suggested that you should visit the RAF Air Defence Radar Museum at Neatishead. The museum posesses a vast knowledge of radar matters in addition to the displays of equipment. They knidly provided some of the information contained in this article. This is one of the best tourist attractions in Norfolk and is well worth a visit. It is not open every day, but a telephone call to the museum on 01692 631485 will give the opening days and times, or visit www.radarmuseum.co.uk

Ramblings from Happisburgh

Narrated by Trevor Stevens to Loughton Library 24 November 2005

My wife agrees that “ramblings” is probably the correct way to describe over sixty-year-old memories, largely disjointed and unsupported by any documentary evidence. It may be a good thing to start at the beginning.

Having been kitted out at Padgate and square-bashed at Great Yarmouth, I passed through the basic radio course at Woolwich Polytechnic, which included some simple metal work. At this stage we were classed as Radio/Wireless Mechanics UT and it was not until being posted to Yatesbury that the difference between Radio and Wireless became clear. We were now RDF Mechanics UT and the Wireless types had gone elsewhere. The school was operating a two-shift system and my class learnt their lessons at night. This had the advantage that we never had to guard the water supply reservoir and could leave the camp during the day. This to the great annoyance of the guards, who were clearly intended to keep airmen in rather than to keep intruders out. Much time was wasted at Yatesbury learning about equipment (C.H. for example) which I at least was never to see again.

On leaving Yatesbury, on Christmas Eve 1941,1 was posted to Happisburgh, pronounced Haisboro (and hereinafter referred to as H), a CHL/GCI Radar situated about halfway between Cromer and Great Yarmouth on the Norfolk coast. Transport collected me and my kit from North Walsham railway station and dumped me at a large rambling farm house called “The Rookery” (now a residential home for adults with learning difficulties) just as the complete Rookery watch were leaving for “The Lighthouse”, a pub a few yards down the road.

So began my stay at H and the serious business of finding out how it all worked.

The radar equipment was installed in two rather tatty timber-framed, barrack type huts separated by a short passage with a door at each end. The passage was used to store PPI tubes in their crates so that they were immediately available if the Controller on duty asked for a change because of a loss of focus. One hut, brightly lit, housed the transmitter, about the size and shape of a very large upright piano, a workbench, table and sundry chairs. This was home to the duty mechanics that had provided themselves with a mattress behind the transmitter where it was both warm and comfortable. The other hut was kept in semi- darkness and housed the receiver with its PPI and Range tubes, the telephone exchange, plotting table, turning gear, tea-making materials etc. Outside was a brick blast wall and, over the top, a wooden gantry supporting the revolving aerial.

A three-watch system was operated for most of the time and on quiet nights I learned how to read map references, and to turn the aerial using the Hopkins two speed turning gear, a vicious manual device capable of giving one a smart rap in any sort of a gale.

It was also possible to stand in the ops room shadows when night fighters from Coltishall were being controlled and to admire the calm efficiency of Squadron Leader Everett and the rest of the team. The aircraft R/T was broadcast in the ops room so that we knew as soon as anybody when an attack had been successful. I was proud to be a member, even though totally ignored and serving no useful purpose whatsoever.

Each morning the duty mechanics, plus the day staff, undertook routine maintenance for one hour which mainly consisted of removing a different panel each day and dusting its top and bottom with a paint brush and vacuum cleaner. The authority who laid down these rules was clearly not of the “If it’s not broke don’t fix it” brigade, and many was the time when re- assembly did not produce the expected results.

Quarterly Overhauls were the same thing but much worse, being carried out by experts who could be guaranteed to leave the equipment in a poor condition. The station mechanics had to put matters right over the next few days. The CHL. at Hopton would be asked to cover when we were off the air and we did the same for them.

Obtaining my LAC (and the money that went with it) involved travelling to Cambridge and sitting a written exam of several hours’ duration. It also involved spending two nights in a small room at Jesus College, high up and near the roof. Washing facilities consisted of a butler sink and a cold tap on a lower floor. I can’t imagine today’s students accepting such poor accommodation.

At about this time two of us were sent to BTH (British Thompson Houston) in Rugby on a course to do with electric motors and selsyns. I think the personnel office was expecting us but the shop floor was not. It was finally agreed that the RAF were not going into the motor manufacturing business so we were sent to a part of the works where motors came in for repair. We handled all kinds of motors, from small fans to motors up to 2 hp, knocking each one to pieces, finding the cause of the problem and writing out a set of instructions to the people who did the work. Motors that were beyond repair were scrapped and those suitable for repair we re-assembled finger-tight and sent on their way. This course saved my bacon on several occasions, once at H and twice with 15054 FDP, when I took motors to pieces for repairs which should not have been undertaken by a mere radar mechanic but which were essential to keep the unit on the air.

Three events happened during 1942 that particularly stick in the mind, the first of which was a bit of a mystery at the time. A number of senior officers arrived and our telephone contacts were told that we were off the air. All operating staff and mechanics were then removed from the ops room. After an hour or so the duty watch was allowed to return, the “scrambled egg” departed in their cars and we were back to normal. We soon found out that other stations in the chain had reported considerable interference but that this was a test of “Window” was not known for a long time. This test was one of the most important of its day. The result so scared the authorities that “Window” was kept under Top Secret wraps and not used in anger until July 1943. What frightened them, of course, was the possibility that the Germans would use “Window” against us.

The second happening required a rather special sort of volunteer. An airman (expendable as always) was put down in a dinghy some miles out at sea by our local Air-Sea Rescue Walrus. Various radar sensitive aerials were used and the miserable airman in his dinghy was moved yet further out to discover the maximum range at which ditched crews could be seen and rescued.

The third involved disturbing dozens of pigeons at the top of H’s church tower. A small aerial was fixed to the top and telephone cable was used to link this aerial with the radar receiver about half a mile away. The signal was fed into the PPI time base circuit so that a perfect horizontal polar diagram was produced on the PPI tube and could be copied on tracing paper. The tracing showed that our aerial system was giving excellent results.

During 1942 workmen had been busy building a new ops block, a gantry, a 180 ft tower and a brick standby diesel house for a new CHL, to be called H2, situated about 200 yards away from HI. The aerials were to be electrically driven and my most vivid memory is of the hoisting of the turning gear and the skill of the tower erectors. H2 was a much more modem set up than HI. Not only was the building of brick and concrete, but it was larger and therefore less crowded and was provided with a rest room, toilets and a simple kitchen. Apart from the electrical turning gear, the basic equipment was much the same as at HI except for the Skiatron, an underused piece of equipment not much suited to CHL operation. It consisted of a flat faced PPI tube of about 3½” in diameter with an intense purple, long afterglow trace. This was projected on to the underside of a frosted perspex table top on which one could record an aircraft’s track. The Skiatron should have been in HI where I’m sure the controllers would have found it useful, but space and technical considerations made this impossible.

For reasons unknown we were involved in commissioning this new equipment. The various bits and pieces worked individually except for the transmitter. The 25KV capacitor was found to be US, although testing it was not easy as all we had was a 500V Megger. Once the capacitor was changed, the transmitter worked and we were on the air. Or were we? The first discovery was that the ground echoes ofH2 were running along the range and the PPI tubes of HI and vice versa. Neither station could work under those conditions.

The cure was to build a small four-valve unit to feed a signal from HI to H2 to lock the two transmitters together but 180° out of phase. The last valve of this new unit was a cathode follower and the signal, a pip, was sent via telephone cable draped over the fence and hedges separating HI and H2. I was most surprised, and relieved, when a beautiful signal turned up on the oscilloscope at H2. End of problems? No!

H2 aerials were of the continuously rotating type and the 360 ft towers of the CH at West Beckham were used to check bearings, signal strength, etc. After only a few revolutions of the gantry aerial it seemed that West Beckham was moving their towers. We assumed that part of the gearing linking the selsyn at the aerial end or the selsyn in the receiver was slipping and much time was wasted in checking the tightness of grub screws. After a great deal of unproductive messing about, it was discovered that one set of gearing had a pinion with 15 teeth, whereas the other had a pinion with 14 teeth. The PPI trace was gaining or losing 1 tooth per revolution of the pinion. The solution was to make a new pinion the hard way (brass rod, hacksaw and files) and that really was the last of the problems at H2 until the WAAF arrived, but that was a very different ramble.

As a result of demands from overseas, male operators and mechanics were posted and WAAF operators arrived at HI (including my future wife Daphne). I was promoted to Corporal and transferred to day work instead of being a watch mechanic.

As soon as H2 was fully operational more WAAF operators arrived, as well as three WAAF mechanics. These girls were reputed to be university graduates and they were certainly very good. Starting the standby diesels was not expected of them.

One evening Eileen, a watch mechanic thought she heard a squeak at the top of the tower and, although it was dark and very windy, she climbed up to find out what was needed. It was a little bit beyond the call of duty. When at the top, she telephoned to say that she did not fancy going down without some help. So I dressed up for the occasion and we came down together. I suspect future wife was not best pleased when told of these goings-on.

As a result of being transferred to day-time time duties I became involved with Flt.Sgt. George Slack in the preparation of the quarterly report. It was a comprehensive load of waffle which covered every aspect of the station’s operation in minute detail. This was done at night and took most of one night to complete. I have no idea where this report finished up but I was informed that it was considered the best of its kind and was used to train future report compilers. Bumph triumphant!

My landlady, Mrs Leeder, prepared a special dinner for us Christmas Eve 1942 to which Daphne was invited. But for me it was not to be. A component of the Centimetric Height Finding (CMH) equipment required welding at Coltishall and I was to take it there on the unit’s motorcycle. An engineer officer and a welder were summoned from their respective messes; the job was completed but the evening was spoilt for quite a number of people.

Although, of course, I did not know it, my time at H was rapidly drawing to an end. When I had arrived the CO was a Flight Sergeant controlling a small number of men. By the time I left the strength of the unit was doubled, the unit was nearly all women and the CO was Flt Officer Matthews. It was almost a pleasure to be hauled up before her for not wearing a hat whilst riding my motorcycle.

Early in 1943 I was promoted to Sergeant and posted in charge of AMES 6083, a light warning unit. This was disbanded shortly before D-day and I then joined 15o54 FDP and went to Europe.

But that is yet another ramble.