The subject of a talk given to the S.A. Military History Society by Dr. F. J. Hewitt on 9th May 1974
I must ask you to forget that we are in the seventies where the achievements of science are taken for granted, and to think back to the late thirties when the Spanish Civil War made it clear to the British public that, in any major war in Europe, they would be in the front line. In the absence of any method of detecting and observing the movements of aircraft there appeared to be no real defence against the bomber by day, let alone by night. How then was the problem of airborne attack on Great Britain largely solved and, in the latter part of the War, a major bombing offensive against occupied Europe maintained? Radar certainly was not solely responsible for this achievement, but radar, or more strictly superiority in radar, played an altogether indispensable role in both defence and offence. Radar also played an indispensable role in anti-submarine warfare which was equally vital to Britain's survival.
Radar, in fact, dates back to before World War II though it was not known as such then. As with all good inventions, at least four countries claim the credit for it - the French, the British, the Americans and, of course, the Russians.
It all depends on what we mean by radar. The definition can become complicated if we try to be too precise. I shall take the simplest. I regard radar as a system for indicating the presence and position of an object by means of the scattering or echoing of radio waves by that object. Radar involves the measurement of the time the radio waves take to travel from their origin to the scattering object, and back. This time element is vital in the definition of radar. By knowing the travel time and the speed of travel of the waves, the range can be determined.
Once we accept that radar involves the transmission of radio waves, the detection of the echo and the measurement of the travel time, we have little difficulty in saying that radar was an American invention. In 1923 two American scientists, Breit and Tuve, used this method for measuring the height of the layer of ionized gas high up in the earth's atmosphere, the ionosphere. They measured the time taken for the waves to reach it and return, which was about a thousandth of a second. Knowing the speed of travel of radio waves, they calculated the height of the layer to be about 160 kilometres.
The word 'radar', coined some twenty years later, is
derived from Radio Detection and Ranging.
As far as military devices are concerned, the position of the United Kingdom is quite clear. As the war clouds gathered in the late thirties, the need for some means of detecting the approach of enemy bombers was becoming more and more pressing. However, the concept of radar arose indirectly. There was then, as there still is today, talk of a death-ray as the ultimate weapon and there were various claims in this regard. The radio physicist, Watson Watt, at the National Physical Laboratory was thus asked by the British Government to report on the possibilities of a death-ray. Watson Watt quickly expressed the view that at that time death-rays were not a practicable proposition but added for good measure that it should nevertheless be possible to detect the presence of aircraft by the reflection of radio waves from them. He was immediately invited to demonstrate this and he did so at short notice by using radio signals from one of the Daventry shortwave radio transmitters. Watson Watt himself was an expert on the ionosphere and fully familiar with the method of Breit and Tuve. The next step to pulsed transmissions was obvious to him and he pursued the matter so vigorously and with such support from the Government and the RAF that by early 1939 there was a chain of operational radar stations along the east coast of England - a chain of stations which remained operational, without any great changes, throughout the War. Watson Watt was knighted at the end of the War for his services, and died recently. I had the privilege of experiencing his remarkable knowledge and ability on many occasions. As far as I am concerned he was the father of radar.
I would like to convey to you something about the South African story but at this stage I must, in the main, give you my story. The whole South African story has yet to be written or, if it has been written, I am not aware of it. My involvement started in January 1940 when I reported as a raw physics graduate to the then Dr Basil Schonland, at the Bernard Price Institute of Geophysical Research at the University of the Witwatersrand. Sir Basil, as I shall call him, had by that time become a world-recognized expert on lightning and I had originally been offered a post with him for lightning research, but late in 1939 Sir Basil had been approached by the Department of Defence and he had put himself and his Institute at their disposal. What had happened was that the British Government had notified Commonwealth countries, in extreme secrecy, of the development of a system for the detection and location of aircraft, RDF (Radio Direction Finding) as it was then called, and had invited them to send senior scientists to the United Kingdom with a view to acquainting them with the principles, so that each country could build up a team who could in due course assist in the introduction of RDF systems as and when they became available.
Sir Basil did not go to the United Kingdom. No one went from South Africa, but instead it was arranged that Sir Basil should meet the distinguished New Zealand scientist, Sir Ernest Marsden, on his return from the United Kingdom to New Zealand. Sir Basil, in fact, met Marsden's ship in Cape Town and travelled round the coast to Durban. Marsden had some rather vague documents in his possession. Copies of these and notes made by Sir Basil on their discussions whilst at sea were all Sir Basil had to work on.
Those of you who may have known Sir Basil will realize that he was not interested in gathering a team in preparation for the arrival of equipment from overseas. He gathered a team without delay - but with the object that they should design equipment themselves and, in fact, they did this with such success that the first radar echo was 'seen' on December 16, 1939. The echo was thought to be from the Northcliff Water Tower. My guess is that it was from the whole of Asvogelskop, but who is to argue that now? The team who did this consisted of Sir Basil Schonland, Professor Bozzoli (now Vice-Chancellor of the University of the Witwatersrand), Dr P. Gane (a geophysicist at the BPI), Professor W. Phillips (now Deputy Vice-Chancellor of the University of Natal) and Noel Roberts from the University of Cape Town. One can only have the very highest regard for their achievement. All they really received from the United Kingdom in the way of guidance was that it could be done and the broadest description of 'how'. They had none of the more advanced electronic components or test equipment that was available in the United Kingdom. For components they bought what was available in Johannesburg on the amateur radio market. Of test equipment and instruments they had very little indeed. They had to improvise for all measurements except the most conventional.
A slightly later version of the first transmitter
Our first sets worked on a wavelength of about 3.5 metres, not far off the wavelength of our present FM service in this country. At that time it was about the shortest wavelength at which we could generate a reasonable amount of power. The valves we used were bought in Johannesburg and were Eimac 250 THs. I can remember this number after thirty years but cannot remember today's date! We were able to generate about five kilowatts with a pulse length of twenty microseconds (twenty millionths of a second). Developing a transmitter to do this was no easy task. The techniques for generating such short pulses were very different from those used in communications and broadcasting. Looking back at this transmitter now, I realize that just about everything was wrong with it, but it worked!
The pulses of radio waves generated by the transmitter (50 per second and too low for efficiency by present day standards) were then radiated by an aerial system which sent out waves in a wide beam - 30 degrees or so wide. This beam could be pointed in any direction by the operator by rotating the whole set-up mechanically. In the early days, a second, identical aerial system was used to receive the very weak echo signals. It had to be pointed in the same direction. Some idea of the aerials used is given in the accompanying picture. The version shown is, in fact, a later model - circa 1941.
Aerial system - From a painting by Official War Artist, Geoffrey Long
Typical display of those days - From a painting by Geoffrey Long
After this short trial period which had really been very successful, we packed up the station and waited for sea transport to Mombasa. Sir Basil flew up. We travelled on 'SS Rajula' with, I think, a Transvaal Scottish Regiment of the 1st Division. We were odd men out. We had had no time for military training but were in a military unit with military ranks. I had done the normal ACF (Active Citizen Force) training pre-war ending up as an NCO but had no officer training. At Mombasa, Movement Control had never heard of us and packed us off to Nairobi, though we knew we were destined for the protection of Mombasa and the convoys supplying the South African Forces in East Africa. At Nairobi we were promptly sent back to Mombasa - not the last time in the next five years that such things were to happen.
Back at Mombasa, attached to the 1st Anti-aircraft Brigade, things were better organized. After a few days we moved up to Mambrui some ten miles north of Malindi and about 100 miles north of Mombasa, where we were to establish the station. Here we encountered serious technical problems. We had not previously operated off a diesel generator and the voltage fluctuations of the single cylinder engine wrought havoc with the timing circuitry - the precision of timing having to be of the order of a millionth of a second. I think that sorting this out in the field was the start of my real relationship with Sir Basil. Over the next fifteen years or more he had a very significant effect on my career, our final close association being in the early fifties when, at his suggestion, I was developing radar for the study of lightning - the full circle.
Our first test flight was disastrous. Half-way through it, there was a smell of burning and a transformer failed. The cause was poor circuit design and we had to make a modification in the field. From then on things went reasonably well and we achieved reasonable serviceability. Our job at Mambrui was to detect possible Italian bombers proceeding down the coast to attack Mombasa. Theory had it that this would take place at dawn and dusk. We, therefore, operated for about fourteen hours a day, with priority for the dawn and dusk periods and the moonlight hours. Only once did we see Italian aircraft. They bombed the airstrip-at Malindi 16 kilometres away. We did not see them coming in but we saw them going out to sea afterwards for 56 kilometres and then lost them because of our restricted coverage arc of 180 degrees. So much for the theory of their flying along the coast. As a result of this we modified our aerials to cover the full 360 degrees - and thenceforth had endless trouble with breaking feeders.
Operationally the station was linked to Mombasa Fortress by HF radio and later an indifferent telephone. The HF radio was also indifferent. We passed plots using an elementary code. The idea was to alert the gun crews and get fighters up. At that time we were not thinking of guiding interceptions. In more active theatres of war such techniques were perforce being developed.
Whilst we were in East Africa work proceeded apace at home. More sets were built, many improvements were introduced and the first steps at the improved handling of the plots from a number of stations by a 'filter room' were taken. In fact, by the end of 1940 when sets were sent up for the protection of Nairobi, a filter room was included. I assisted briefly with the installation of a set at Thika near Nairobi and then went to Mombasa where an entirely different type of set had arrived from South Africa. This was designed to guide searchlights by providing an accurate bearing and to give accurate range to anti-aircraft guns. It had a claimed bearing accuracy of about a degree and a range accuracy of several hundred metres, far in excess of what otherwise was available, but the set was not properly developed and, for mechanical reasons in particular, it had to be abandoned.
I went up to Egypt in April 1941 in preparation for the move of the East African stations to the Middle East. These were to be fully integrated with the RAF and together we selected sites on the coast of Sinai. The stations at El Arish, Rafa and El Midan were operational by mid-1941. We passed our plots to the RAF filter room at Ismailia and we had our first experience of real operations. The stations performed well and much better than in Nairobi because, at this wavelength, performance over the sea is better than over land. We frequently plotted hostile bombers at ranges of around 120 kilometres and the stations operated there for a year or so. I left in November 1941, and the stations closed in the course of 1942, I think, and were replaced by very large RAF stations.
In South Africa during this time the Unit, the Special Signals Services, had grown considerably. Stations were established at the four ports using South African built equipment initially, though with British CD/CHL sets introduced at Signal Hill, Cape Town and in Durban early on. The South African Stations were used originally for the tracking of shipping but, with the return of personnel from the Middle East, procedures were adopted for aircraft observations as well. These radar sets (RDF at that time) were very simple. Other developments were coming thick and fast. The first we encountered in South Africa was the ASV (air to surface vessel). This was a lightweight set carried in aircraft for coastal patrol duties. In the early days its range on shipping was perhaps 16-32 kilometres and it could see a surfaced submarine but not a periscope. Our main problem lay in aerial installations - aeroplanes and large aerials are scarcely compatible. If I remember rightly, mid-1942 involved some of my colleagues heavily in installing ASVs in the first Lockheed Venturas.
Besides the ASV there were many exciting developments in the United Kingdom where applied research was active as never before. I was fortunate in being sent to the United Kingdom in 1942 to study a completely new development, microwave radar. A brilliant achievement at the University of Birmingham had led to the possibility of radar at a wavelength of ten centimetres. This made possible very narrow beams, freedom from the effects of ground and performance from small aerials never obtainable before. This invention was the cavity magnetron.
In the United Kingdom microwave radar made possible really effective airborne radar, known as AI (Air Interception) for night fighters for defence against night bombers, but it was quickly proved to be a major weapon of offence as a navigation and bombing aid of unprecedented versatility. This system was known as H2S. Microwave radar in a bomber presents the pilot with a map-like picture of the ground over which he is flying. Coastlines, rivers, towns and even large bridges can be seen. Such a system, of course, is entirely independent of ground radio stations and aircraft could thus operate beyond the range of the precise radio position fixing systems that had also been developed, such as Gee, H and Oboe. These three systems were closely related to radar and had quite unprecedented accuracy, but their range was limited. These radar devices, highly accurate up to the range of the ground stations, less accurate but invaluable beyond the range of the ground stations, were the key to the whole night bomber offensive of the RAF. I think the invention of the magnetron, vital to H2S and AI and in due course ASV, is recognized as the most significant invention of the War. Churchill himself in his World War II memoirs refers to the 'decisive role played by H2S' and deals with the whole subject in surprising detail. Many of the famous Churchill memos deal with radar.
My interest in centimetric radar in the United Kingdom was firstly to study the completely new techniques involved and a microwave radar set developed for naval use for the detection of surfaced submarines. Sir Basil Schonland had persuaded the Royal Navy to make available two such sets to be installed in the Cape. He argued that such a set on the top of Table Mountain would have a range on a surfaced submarine of nearly 160 kilometres. Back in South Africa in 1943, we installed the sets on Signal Hill and at Cape Point where they gave excellent results and greatly strengthened the coverage provided for the previous year or so by the South African sets. We did, however, have many operational problems. We had no way of distinguishing fishing boats from other small objects. There was no control on fishing boat movements and aircraft, sent out to identify suspicious echoes, became annoyed at finding fishing boats. We felt it hardly fair that radar should be blamed. Also our South African sets in particular were notoriously inaccurate in their bearings and at times would produce erratic tracks with apparent bursts of high speed on the part of the target, solely due to inaccuracies. I was posted to Cape Town at the beginning of 1943 as Company Commander fresh back from the United Kingdom and centimetric radar, and within the first two weeks three large ships went aground. Each had been plotted by the coastal radar system for some two hours before it struck. One ship went aground right in Camps Bay. You can imagine the post-mortems. It was quite a baptism of fire for me. Hasty measures were introduced by the operational people to warn ships approaching the coast of possible danger. A few weeks before we installed a centimetric radar at Saldanha Bay, another ship went aground right next to the harbour entrance. It was carrying two further centimetric radars for us. We managed to get on board the ship and salvaged the sets which had then been immersed in a mixture of sea water and potassium permanganate for several weeks. Surprisingly enough, in due course, we got one to work.
At about this time a most sophisticated anti-submarine radar arrived unheralded in South Africa in the first Lockheed P VI aircraft to come to this country. This was a three centimetre radar known as ASD. Beautifully designed and constructed, it was one of the first products of the American electronics industry after the concept of the cavity magnetron, referred to earlier, had been given to the United States by the United Kingdom. This set was used extensively on coastal patrols. Towards the end of the war one of these ASD sets was specially fitted to Field Marshal Smuts's York, not for anti-submarine purposes but for navigation in the way mentioned earlier for the airborne radar used in bombers. These three-centimetre wavelength sets were also excellent for detecting thunderstorms and heavy rain and were invaluable for flying through the tropics at night. Improved versions of this type of set are, of course, fitted in all modern civil aircraft largely for this purpose.
In South Africa, for our coastal defence purposes, we thus relied for the first two or three years of the war on our locally designed and built equipment. Gradually larger and more sophisticated sets became available from the United Kingdom. By late 1943 we had a fairly extensive system for the detection of surfaced submarines, surface vessels, low- and high-flying aircraft. We also had limited facilities for directing fighter aircraft to intercept unidentified aircraft detected by the radar system. This particular facility was provided by a special type of set known as a GCI (Ground Control Interception). It had been developed in the United Kingdom in the critical 1940/41 era for night bomber interception. Basically it was a conventional radar set as described previously but the aerial system, and hence the beam it transmitted, rotated several times a minute providing the controller with an elementary picture of the tracks of all aircraft within range. By means of this and knowing which aircraft was the fighter the controller could issue instructions as to how to intercept. The stations we installed here were relatively elementary. The threat of air attack had decreased by then and the more sophisticated equipment used in the United Kingdom towards the end of the war was never installed in South Africa during the war. When our South African stations in Sinai were dismantled the crews were in the main attached to the RAF and operated GCIs of this nature in the Italian campaign. I had no personal experience of this.
Other activities in which we were involved in South Africa were special types of radar for anti-aircraft fire control and for coastal artillery fire control. One of these sets known as the GL II (Gun laying), a relatively long wavelength radar of British origin, somewhat outdated even then but excellently engineered to its maximum potential, had borne the brunt of the anti-aircraft fire control for the defence of London during the early blitz. I remember seeing remarkable figures of 'rounds per bird', as they call it, in the various phases of the blitz. If I remember rightly, in the early stages prior to the GL II something like 75 000 rounds of anti-aircraft ammunition were fired for each aircraft shot down. Using GL II anti-aircraft fire-control once the techniques had been developed, this figure came down to about 2 000. Later with the centimetric fire-control the figure was about 800. The flying bomb (an ideal target, because of its flying straight and at a constant speed) with centimetric fire-control and electronic predictor and proximity-fused ammunition, was almost a sitting duck. But of course the flying bombs did not always fly within range of the batteries - they flew so low. I mention these figures from London in what is essentially a South African talk because, in fact, South Africa played a part here through Sir Basil Schonland. He was on loan to the British Government at the time and was the Superintendent of the Army Operating Research Group. His Group played a major part in analysing anti-aircraft fire-control practices and in developing procedures to increase the accuracy. I myself was in the United Kingdom during 1944/45, reporting to him on other duties, so I was aware at least of what he was doing. For this reason also I am not well informed on the closing phases in South Africa in so far as radar is concerned. As far as the overseas story is concerned my remarks have been most superficial for the subject is vast and complicated.
My remarks have largely been directed at the technical side, with very little about the personnel involved. Two names must be mentioned - Col. Hodges, previously Professor Hodges of the University of Natal, who took over command of the Unit concerned late in 1940 after the first of us had gone to East Africa. He came up to Nairobi at the turn of the year and was OC whilst we were operating in Sinai. Later he returned to South Africa as activities at home increased. I must also mention the name of Brigadier F.C. Collins, Director of Signals through the whole period. His confidence in a Unit with so many academics in key positions was remarkable.
The technical staff initially consisted mainly of electrical engineering graduates and as many electronic technicians as could be found. There was a sprinkling of physicists and mechanical engineers. Operators initially were a great problem. In East Africa and the Middle East we had men from all walks of life. Some were very bright and some were not. I remember an operator who had never read the time to closer than the nearest five minutes and we expected him to read ranges based on measurements to microseconds, and to plot ranges and bearings accurately and read off co-ordinates to three significant figures. In South Africa the problem was solved by using women operators. A very high standard of recruit was attracted and a high level of operating efficiency was achieved under conditions which frequently must have been both boring and tiring.
I have placed prime emphasis on the technical side because I believe the early technical achievements were most remarkable. Having been associated with electronics and telecommunications research and development ever since, I never cease to wonder at the pace achieved in the late 1939 early 1940 phase in a field full of baffling problems. There was, in fact, a happy post-war sequel. Six junior members of this team formed the basis of the Telecommunications Research Laboratory set up by Sir Basil Schonland as part of the CSIR, in 1946. This team remained together for more than ten years and, in fact, in 1957 when Sputnik 1 was launched unheralded, the team showed it had not lost touch. Within two days, (a weekend in fact) tracking equipment was improvised and the orbit of the satellite was established. Within a fortnight one of the members (since then unfortunately emigrated to the USA) calculated the expected lifetime of the satellite in terms of this orbit, and published his results in 'Nature'. He thus gave the world the first and, I think, only reasonably accurate prediction of the lifetime of Sputnik 1 - an event that proved him correct to within 15 per cent. Quite remarkable! The team subsequently dispersed; perhaps just as well as electronics technology is essentially a young man's field.
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