Jod Bank 1.Indd 56 23/10/2019 08:11 Feature

Feature

Radio Eye on the Sky (Part I)

Dr Bruce Taylor HB9ANY Dr Bruce Taylor HB9ANY relates how chance, [email protected] skill, tenacity and the enthusiasm of a botanist n July 7th 2019 Jodrell Bank radio amateur created a technical masterpiece. Observatory, the home of what is surely the most iconic radio antenna in the world, was de- claredO a World Heritage Site in the same cultural category as the Great Wall of China and the Pyramid Fields from Giza to Dahshur. It was recognised by UNESCO as “a masterpiece of human creative genius” because of its scientifi c achievements in advancing our understanding of the uni- verse. But as the champagne fl owed in cel- ebration of this magnifi cent accolade, few remembered that 62 years earlier its found- er, Bernard Lovell, endured immense per- sonal hardship and narrowly escaped incar- ceration during the technical, political and fi nancial drama surrounding its creation. In 1939, 25 year-old Lovell was one of many talented university teachers and re- searchers who abandoned their peaceful studies to join the war effort. They teamed up with hundreds of radio amateurs and professional electronics experts who contributed their technical skills to the defence of the United Kingdom. Lovell was just about to set out from Manchester for the Pyrenees, in a small van loaded with equip- 1 ment for cosmic ray research, when he received a call to report to the Chain Home at which available thermionic valves could (CH) laboratories at Bawdsey Manor on generate signifi cant power was about the east coast of England. When he asked 200MHz, which severely limited the sharp- why, he was told “You will soon learn!”. The ness of the polar diagram of any antenna origins of the huge antenna that would that could be carried by a small plane. This later be named the Lovell Telescope can in turn restricted the maximum range at be traced to his visit to a CH radar station which the equipment could operate before near Scarborough, when the WAAF opera- the target echoes were masked by ground tor explained that some of the echoes on returns. her cathode ray tube (CRT) display were not Although later incarnations of this 1.5m from aircraft but refl ections from the iono- AI radar were eventually used with consid- 2 sphere. erable success, the key to enhanced performance was the development of the high oped a split beam technique that allowed AI Radar power 10cm (S Band) cavity magnetron at an AI radar to ‘lock-follow’ a target, as well As early as 1936, Henry Tizard’s air defence Birmingham University. The magnetron de- as a ground version that could track an air- committee had foreseen that if daytime sign was refi ned by Eric Megaw GI6MU, a craft with an accuracy of better than one attacks by the Luftwaffe were thwarted, keen radio amateur known for his pioneer- degree. However, on January 1st 1942 he Göring would turn to night bombing of ing DX feats during the 1920s, and rushed was assigned an entirely new task; one that the UK instead. Lovell’s fi rst task was to into production by GEC at Wembley. Lovell shattered his idealistic view that war in- develop an improved airborne intercep- did fundamental studies on aircraft radome volved only the defence of the realm. tion (AI) radar system compact enough to materials and centimetric antennas, re- be installed in a night fi ghter, but accurate placing the 2m long horn used for initial ex- H2S enough to track an aircraft from a range of periments with a more compact parabolic After the evacuation of Dunkirk and the fall several miles down to 500 to 1000ft, so that refl ector, a small foretaste of what was to of France, strategic bombing was the only it could be identifi ed visually before open- come at Manchester. Using an offset dual- means by which damage could be infl icted ing fi re. At that time the highest frequency dipole feed rotating at 800rpm, he devel- on the enemy. But contrary to the optimistic

56 PRACTICAL WIRELESS December 2019

Jod Bank 1.indd 56 23/10/2019 08:11 Feature

Halifax that caused the deaths of the crew and key members of the EMI team, including the electronics wizard Alan Blumlein. In addition to his radar developments, such as the line-type pulse modulator, Blumlein’s many inventions included the slot antenna, directional microphone technique, stereo sound, the transformer ratio arm bridge and much of the pre-war Marconi-EMI television system. Lovell was rushed to the crash site to recover the magnetron anode core before it could fall into the wrong hands. Because of wartime secrecy, details of the crash were not revealed to the public. An enquiry established that the cause was simply the improper tightening of a tappet locknut during a routine engine inspection shortly before the fl ight. This caused the in- let valve stem to fracture, igniting the super- charged mixture in the induction manifold and leading to a major fi re in the engine na- 3 celle, which spread rapidly to the fuel tanks in the wing. One reason that none of the scientifi c personnel jumped to safety may have been that there was an insuffi cient number of parachutes on board. Churchill himself immediately issued a directive that this should never be allowed on future test fl ights with civilians. In spite of the loss, Churchill insisted that RAF squadrons be equipped with 200 H2S systems in the following three months. When Lovell protested that as a result of the crash he no longer even had a single prototype, he was told “Young man, you’ve lost one aircraft. Don’t you realise we lost 30 over Germany last night?” ASV Lovell’s conscience was troubled by the fact that he had contributed to the development of an instrument which would greatly 4 improve the performance of an offensive Photo 1: Jodrell Bank Observatory is now a UNESCO World Heritage Site. (Ian Morison, Jodrell Bank) force that would cause devastating loss of Photo 2: Bernard Lovell in 1958. (Jodrell Bank) Photo 3: Eric Megaw GI6MU made the 8-cavity life. These feelings were mitigated to some magnetron that was taken to the US by the Tizard Mission. (Canada Science and Technology Museum) extent by the fact that H2S was also sub- Photo 4: H2S indicator in the navigator’s position of a Lancaster. (Crown Copyright) sequently modifi ed to perform as a 10cm Air-to-Surface Vessel (ASV) radar that was reports by aircrews, photo-reconnaissance had proved a problem for AI radar might be used very successfully to locate U-boats as revealed that two-thirds of the RAF’s night the key to solving the navigation problem. they crossed the Bay of Biscay from their bombers failed to strike within fi ve miles of Lovell was assigned responsibility for the fortifi ed pens to wreak havoc on the Allied their targets. With the lack of reliable me- development of this centimetric mapping Atlantic convoys. The centimetric ASV ra- teorological data over enemy territory, navi- radar, which was dubbed H2S. Handley dar replaced the old 1.5m version, which gation by dead reckoning was approximate Page were initially reluctant to modify their became obsolete when the U-boats were at best. Although precision blind bombing Halifax bomber to carry a large radome un- equipped with Metox listening devices for systems such as Oboe were being devel- der the fuselage, since it would seriously that wavelength. In a few weeks 37 U-boats oped, they had limited range because they reduce the bomb load. But they accepted were sunk and the merchant shipping loss- depended on radio transmissions from the the argument that it would be better to drop es decreased dramatically. UK. some bombs in the right place than to scat- Lovell’s team also developed versions of It was soon realised that, with a suitable ter a full load over the open countryside! H2S for navigating and ranging with tank rotating antenna and plan position indica- The development went ahead rapidly but landing craft, and this Scent Spray system tor (PPI) display, the ground refl ections that suffered a major setback with the crash of a was used in the invasion of Sicily and the

Enter our competitions at www.radioenthusiast.co.uk/competitions

December 2019 PRACTICAL WIRELESS 57

Jod Bank 1.indd 57 23/10/2019 08:11 Feature

5 7

D-Day landings. To obtain the higher reso- Lovell soon found that at Manchester During the post-war years large quanti- lution required for the precise selection of University the local QRM from sparking ties of excellent electronic equipment be- targets, some Lancaster bombers were overhead DC tramway lines made the re- came available as Government Surplus. equipped with roll-stabilised 6ft whirligig ception of weak signals impossible, even This was a golden age for radio experi- scanners instead of the original 3ft ones, in the early hours of Sunday morning. The menters, who could acquire a huge range and with new magnetrons the operating problem seemed insoluble until he made of components and complete transmitters, wavelength was reduced to 3cm (X Band). a chance encounter with a university bota- receivers, CRT indicators, amplifi ers, power Very high resolution 1.25cm (K Band) sys- nist, Frederick Sansome, who happened to supplies and test instruments for a frac- tems were also produced, although they be a keen radio amateur. As soon as Lovell tion of what they had cost to manufacture. suffered from signal attenuation in cloud explained his project Sansome became Some items, such as HRO, AR88 and CR100 and became more useful as weather ra- most enthusiastic about it, and immediate- receivers, were still popular with radio ama- dars. Later versions of H2S were installed ly offered the use of an isolated fi eld in the teurs 20 years after the end of the confl ict. in Canberra bombers and the V-force air- open country about 25 miles south of the Lovell was quick to realise the value of craft. They were used by Avro Vulcans dur- university, in which he carried out botanical such equipment for research work, and ing the 1982 Falklands War, and Mk IX units experiments. The area was called Jodrell he acquired a large amount of it through with 200kW magnetrons remained in ser- Bank. Little did either of the men know at his wartime contacts. He obtained more vice until 1993. the time that this muddy carrot fi eld would army receivers and transmitters, recov- in due course become the site of a world ered equipment from the Admiralty, and Jodrell Bank class radio astronomy facility. was authorised by an Air Marshal to take Following his release from military work in Lovell’s army radar trailers were soon away almost anything he wanted for a pay- 1945, Lovell accepted a post as a physics towed to Jodrell Bank, where they quickly ment of £10. As a result, when the Perseids lecturer at Manchester University, with bogged down in the mud. With the help of meteor shower came around in August a salary of £550 per annum. He initially a neighbouring farmer the fuel pipes of the 1946 he had equipment that had cost more wanted to take up the work on radio diesel engine were cleared of ice and the ra- than £1m set up around the muddy fi eld at echoes from cosmic ray showers that he dar set was powered up. Lovell was excited Jodrell Bank, including a Park Royal truck of had planned six years earlier. During the and surprised to fi nd that the CRT showed sophisticated receiving and display equip- immediate post-war period of shortages, several transient echoes per hour, a much ment. An ex-army searchlight was adapted materials such as steel, wood and copper higher rate than he expected from cosmic as the steerable base for a broadside array were strictly reserved for national needs ray ionisation. of Yagi antennas with high directivity. The and building a large high-gain antenna for motley collection of Jodrell trailers, genera- research work was out of the question. Meteor Scatter tors and antennas soon became known lo- But he was able to negotiate the loan of It turned out that such echoes had previ- cally as The Fairground, and the scientifi c a mobile 70MHz (4m) 150kW army radar ously been observed when the equipment results achieved there were astounding. consisting of a transmitter and receiver was used for the detection of V2 rockets, Radio amateurs who practice mete- with CRT display in two trailer cabins and a and they had triggered a number of false or scatter communication know that the trolley-mounted 3-cylinder diesel generator, alarms. It was suspected that they were predawn hours are the most favourable for and these were delivered to the university. caused by the ionisation produced by me- making QSOs. Lovell’s team worked long The system was one of 50 that had been teors entering the earth’s atmosphere at a shifts in arduous conditions in all weathers modifi ed with elevated Yagi antennas for height of about 100km. This was confi rmed to make thousands of meteor recordings the detection of V2 rockets. by experiments about eight months later. and correlate them with visual sightings.

58 PRACTICAL WIRELESS December 2019

Jod Bank 1.indd 58 23/10/2019 08:11 Feature

Photo 5: Day One at Jodrell Bank. The 70MHz trailer receiver cabin beside the botany huts. (University of Manchester) Photo 6: An ex-army searchlight provided the steerable mount for an array of ﬁ ve 8-element Yagis. It is now Grade II listed. (University of Manchester) Photo 7: The ‘Fairground’, with the 218ft transit antenna centre left and the botanical huts upper right. (Jodrell Bank) Photo 8: The beam direction of the transit antenna could be altered by tilting the 125ft feed mast by up to 15°. (University of Manchester)

Using the ‘searchlight antenna’ they also detected previously unknown daylight showers that were invisible to the human eye. By setting up apparatus to measure the veloc- ity of the meteors, they were able to resolve a fundamental controversy among astronomers by showing that the sporadic meteors are not of interstellar origin but have closed orbits around our sun. Two key outcomes from these meteor scatter studies were in due course to have a major inﬂ uence on the destiny of Jodrell Bank. First, the searchlight antenna showed the great utility of a high-gain antenna that could be steered precisely in azimuth and elevation and that had unrestricted sky cov- erage. More fundamentally, the community of astronomers learned how radio and radar observations provided an entirely new technique that could be of immense value to our understanding of the cosmos.

The Transit Antenna 8 As a fi rst step towards a higher gain antenna with narrower beamwidth, Lovell The farmer who had helped start the die- tion. However, radio amateur Grote Reber constructed a ground-level fi xed parabol- sel generator was a great help during the W9GFZ heard of Jansky’s discovery and ic wire bowl, 218ft in diameter, which had construction of the antenna, for he believed built a 31ft diameter parabolic refl ector a gain of about 28dBi at 70MHz. The pe- that radiation from a radar set had been (tiltable but not rotatable) in his backyard to rimeter ring was supported by 24 scaffold the cause of a bumper grain crop in his continue investigations. After unsuccess- poles, from which 3/8in radial steel cables fi eld adjacent to the Fairground. Puzzled by ful experiments at 3300MHz and 900MHz, were strung to the centre. Each cable was this phenomenon, the university botanists Reber fi nally detected radiation from space strained to concrete blocks in the ground agreed to compare the yields from radi- at 160MHz, and he made his fi rst RF sky at three points, to approximate the ideal ated and non-radiated fi elds the following map in 1941. parabolic shape with a maximum devia- season, but they observed that the irradi- By 1923 radio amateurs had surprised tion of 5in. The mesh refl ector was made ated fi eld had a much poorer crop that year. professional scientists when they discov- from eight miles of 16-gauge galvanised It transpired that the farmer was so con- ered that effi cient DX propagation was pos- iron wire, wound on to the web of cables vinced of the positive effect of the radiation sible on short wavelengths because of the by hand. Because of leakage through the that he had abandoned the use of fertiliser unsuspected existence of the ionosphere. mesh, the gain only increased to 33dBi at in that fi eld! Similarly, Reber’s amateur observation 144MHz. Since the bowl was relatively shal- While the 218ft antenna provided 70MHz that the cosmic radiation diminished with low, the focus of this transit antenna was radar refl ections from meteor trails, it frequency contradicted existing theory. 126ft above the ground. After abandoning failed to detect any echoes from cosmic Only later was it understood that this was an initial attempt to use the wooden tower ray showers. But it revealed phenomena because the synchrotron radiation from of a CH receiving station to support the that were to open a new chapter in radio electrons moving at high speed in magnet- primary feed, 126ft of narrow steel tubing science. As early as 1931 the Bell Labs ic fi elds is much more powerful than the was obtained and secured vertically with radio engineer Karl Jansky had discov- blackbody thermal radiation at radio wave- guy wires. Strong nerves were required to ered that radio noise was emitted from our lengths. solder a coaxial cable when changing the Milky Way galaxy, but neither his employer As the rotation of the earth swept the 2° primary feed while clinging to the top of this nor the world’s astronomical observato- wide lobe of the transit telescope through mast. ries showed much interest in this observa- a strip of sky at the zenith, Lovell observed

Enter our competitions at www.radioenthusiast.co.uk/competitions

December 2019 PRACTICAL WIRELESS 59

Jod Bank 1.indd 59 23/10/2019 08:11 Feature

9 10

several localised peaks in the cosmic radio noise level. The RAF obligingly fl ew an aircraft with a small transmitter in various directions across the antenna, allowing the polar diagram to be measured accurately. The only way to tilt the beam away from the zenith was to manually adjust the lengths of the 18 guys that supported the 126ft central mast, an arduous procedure that had to be done very gradually to avoid buckling. By tilting the mast to the limits of safety and respectable beam shape, the acces- sible strip of sky could be deviated just enough to include the M31 spiral nebula, the nearest extragalactic nebula similar to the Milky Way. After three months of tilting and scanning, a contour map of M31 was completed, showing that radio waves were coming from a galaxy other than our 11 own, two million light-years distant. In view of the strength of the radiation this conclu- calculated value. Accurate range measure- Photo 9: Replica of Karl Jansky’s 14MHz sion was hotly disputed by many research- ments showed that both phenomena were 8-element Bruce array at the NRAO in Green ers, who attributed it to unseen radio stars caused by the unexpected fact that the Bank, West Virginia. (Jarek Tuszyński/CC-BY- in the Milky Way. The dispute was only re- radio signals were returned mainly from a SA-3.0 & GDFL) Photo 10: Grote Reber W9GFZ solved in favour of the extragalactic hypoth- region at the centre of the lunar disk, with a built this 31ft diameter parabolic dish in his back esis four years later. radius about one third of the total. Whereas yard. (NSF/AUI) Photo 11: The transit antenna the time difference between signals scat- was later equipped with a steel lattice feed tower Moonbounce tered from the centre and the periphery that could be manoeuvred by an electric winch. While radar echoes from the moon were would be about 11.6ms, the effective depth (University of Manchester) fi rst recorded at Jodrell Bank in 1949, it of the moon is actually less than 1ms. wasn’t until 1953 that a systematic study of To explore the cause of the slow fading, In view of the successes with the 218ft the earth-moon-earth (EME) path began. At the signals refl ected from the moon were paraboloid and other facilities at Jodrell 120MHz the returned signals showed both received on a separate 25ft diameter para- Bank, Lovell began to dream of a very large a rapid fading with a period of a few sec- bolic antenna that had been recovered from antenna whose beam could be directed to onds and a longer fading period of the order an exhibit at the 1951 Festival of Britain. any part of the sky, so that he could explore of 30 minutes. By comparing the rate of the Switching the receiver between orthogonal the discrete localised sources and make a short-period fading with the orbital position dipoles in the antenna showed conclusive- detailed radio survey of the heavens. Little of the moon, Lovell’s team showed that it ly that the fading was caused by Faraday did he realise how diffi cult it would be to was caused by libration (the apparent rock- rotation of the polarisation as the waves turn the dream into reality. ing of the moon due to its varying distance passed through the ionosphere in the pres- Next month I will describe the saga of the from the earth). But the correlation between ence of the earth’s magnetic fi eld. This ef- construction of the 250ft diameter Lovell the strength of successive echoes was only fect is quite signifi cant for 144MHz moon- Telescope and how the antenna project half of that predicted, and the refl ection co- bounce communications but less so on was saved in extremis by the dawn of the effi cient of the moon was one tenth of the 23cm and shorter wavelengths. space age.

60 PRACTICAL WIRELESS December 2019

Jod Bank 1.indd 60 23/10/2019 08:12 Feature

Radio Eye on the Sky (Part II)

Dr Bruce Taylor HB9ANY Dr Bruce Taylor HB9ANY concludes the story [email protected] of the origins of Jodrell Bank with the saga of the ith the aid of a few construction of the iconic Lovell Telescope. colleagues and a farmer, Bernard Lovell had successfully built a static 218ftW diameter parabolic dish antenna for £1000, using garden spades to mix the concrete for the foundations and wooden ladders to erect the wires of the refl ector bowl. So surely it would be straightforward for a large fi rm of experienced professional structural engineers to construct a slightly bigger version that could also be steered in any direction? Perhaps for around £50,000? Hence it came as a surprise that most of the engineering fi rms approached by Lovell said that it was impossible, and the fi rst company that did accept the design challenge said that it couldn’t be built for less than £250,000. So it was a relief that when the Sheffi eld consulting engineer Charles Husband visited Jodrell 1 he declared “It should be easy – about the same problem as throwing a swing bridge across the Thames at Westminster” and they would be “reasonably safe with a fi gure of £100,000”. The fi nal bill was £750,000; over £20m in today’s money. During the war, Husband had worked on aircraft manufacture for the Ministry of Works and in 1946 he designed a facility for testing jet engines at altitude. His prestigious company designed many fi ne bridges and would later go on to design the antennas for the Goonhilly satellite earth station, Sri Lanka’s tallest building and the replacement Britannia Bridge after Robert 1 Stephenson’s structure was destroyed by 2a 2b fi r e i n 1 9 7 0 . fully justifi ed the project by an impressive with the detailed design study and it Go-Ahead list of possible scientifi c applications, appeared that there wasn’t a cloud in the In February 1950 support for the fi rst phase Appleton remarked with judicious foresight sky. Passing joyfully through Trafalgar of the project was given in remarkably that the greatest use of the antenna might Square as he left the meeting, Lovell was short time at a critical meeting of the Royal be for fi elds of research that couldn’t be thrilled to think that the top of Nelson’s Astronomical Society in the Edinburgh envisaged at the time. column was merely at the height of the University apartments of Sir Edward Lovell and Husband lost no time in trunnion axis of the splendid antenna that Appleton. £3300 was allocated to allow making an application to the Department he proposed to build. Little did he realise Husband to prepare a detailed design for of Scientifi c and Industrial Research (DSIR) then what endless tangles and frustrations a 250ft diameter antenna, so that tenders for £120,000 for the construction of the lay ahead. could be invited for its construction. Lovell antenna, a control building and other A fi rst problem arose with the acquisition recalled later that it was perhaps fortunate works, such as sinking a borehole on the of the preferred fi eld for the construction, that his distinguished Cambridge rival, site to determine what foundations would which became the subject of a disputed Martin Ryle G3CY, wasn’t present at the be required. At a meeting of the Research estate following the death of the elderly meeting, since his own antenna proposal Grants Committee on June 22nd Lovell lady owner during negotiations for its was in an earlier phase. Although Lovell received immediate authority to proceed purchase. Lovell found himself emmeshed

46 PRACTICAL WIRELESS January 2020

Jod Bank 2.indd 46 18/11/2019 08:04 Feature

Photo 1: The success of the 218ft ﬁ xed transit antenna underpinned the ambition to build a fully steerable paraboloid of similar aperture. (Glyn Evans) Photo 2: The 27ft diameter gun turret rack (left) and trunnion assembly with large roller bearing (right) were hoisted in 1955. (Jodrell 4 Bank) Photo 3: The two cranes have just hoisted the trunnion bearing to the northern tower. (Jodrell Bank) Photo 4: The beginnings of the paraboloid are apparent as the ribs are mounted. For scale, note the two men working on the right side outer connecting panel. (Jodrell Bank) Photo 5: During construction the skeleton bowl was supported by 90 miles of scaffold tubing. (Jodrell Bank)

in family quarrels, which again and again held up a near agreement. Faced with a deadlock, the piling contractors had even begun boring in another fi eld when a High Court decision fi nally settled the legal problem. Transferring the work to the fi nal site was at one stage blocked after a tractor was seen operating in the fi eld during the night. An irate farmer was found to have demolished the contractor’s hut, throwing it into a ditch together with all the marking-out pegs, and placed a ferocious bull in the fi eld! 5 First Steps From July 1950 onwards, Lovell and gear racks to drive the dish in elevation, wouldn’t have been possible to mount a Husband were in almost daily contact and which would cost many thousands of 250ft diameter antenna on an inclined even the severest winter weather didn’t pounds to manufacture. Fortunately, the equatorial mount parallel to the earth’s stop Husband making regular journeys battleships Royal Sovereign and Revenge axis of rotation. Instead, it would have across the Pennines from Sheffi eld to were at that time being broken up by Thos to be turned in azimuth on a circular Jodrell. No one could have foreseen W Ward in Inverkeithing. The 27ft diameter railway track, and tilted independently in the bitter confl ict that would arise a few internal-tooth racks from the 15in gun elevation on a horizontal axis 180ft above years later after an important government turrets hadn’t yet been destroyed and they the ground. But the narrow beam of the committee censured them for lack of were procured with their pinions for their antenna would have to track objects in the contact. scrap value and transported to Manchester heavens with very high precision. Today, The fi rst major technical problem was for a total cost of only £1000. a PC or microcomputer could easily solve the need for a pair of enormous circular Unlike large optical telescopes, it the equations of spherical trigonometry

Enter our competitions at www.radioenthusiast.co.uk/competitions

January 2020 PRACTICAL WIRELESS 47

Jod Bank 2.indd 47 18/11/2019 08:04 Feature

7 8

to produce the az-el signals to drive the dropped, and in due course Brush delivered more steel stiffening had to be added antenna in sidereal motion. But in 1950 a satisfactory drive system on time. to the design. With the addition of other this had to be done by a complex analogue The drive system was not the only item items, such as lifts in the supporting system that eventually comprised 50 that ran over budget, and a year after the towers, the estimated cost of the antenna magslip resolvers. It was replaced by a original estimate of £120,000 the fi gure rose to £439,000. Ferranti Argus computer in 1970. had more than doubled to £242,000, a very By 1954, the Soviet Union was making The Metropolitan-Vickers metadynes substantial sum in 1951. Prices had risen rapid progress with the development used for controlling battleship turrets also by £20,000; the cost of the foundations had of ballistic missiles, which could only inspired the fi rst studies of the antenna been underestimated by £20,000, and an be detected at long range by a radar drive system. Metrovick estimated a alarming discovery had been made about with an antenna having high gain at cost of £28,600 for a Ward Leonard drive the design of the antenna. centimetric wavelengths. It was thought system with a pair of 50hp DC motors that Lovell’s antenna might have a role to on the bogies of the supporting towers The Reflector play in defence, either for making tests to rotate the antenna in azimuth, and Initially it had been planned that the or even operationally. For the refl ector another pair in the towers to drive the parabolic refl ecting surface would to perform effi ciently at 10cm, the mesh dish in elevation. But within two years it comprise a wire mesh with a relatively size would have to be reduced to 0.75in, became evident that this estimate was an coarse opening of 4 x 4in. However, the supporting framework would have irresponsible guess, the price had almost calculations showed that at 300MHz, the to be stiffened, and the tower holding doubled, and the drive system contract had highest frequency of intended operation, the feed at the focus would have to be become a nightmare. this would result in 20% of the incoming made more rigid. Lovell agreed to make With little possibility of additional radiation being lost. To reduce the loss these modifi cations for the Air Ministry in funding from the DSIR, Husband to an acceptable 2%, the mesh opening exchange for a payment of £46,000. In the approached Siemens in Germany, who would have to be reduced to 2 x 2in and the event the payment was never made, since proposed a system at a much lower price amount of steel in the structure would have the required funds weren’t available in the that could be delivered in nine months to be increased to support the greater load. defence budget. But it was too late. The instead of three years. There followed a In 1951 observers in Australia, Holland drawings for the modifi cations had already number of manoeuvres and intrigues that and the USA almost simultaneously been issued, and in any case Lovell felt that held up the placement of an order until discovered spectral line emission from the work should go ahead as it was in the 1956. Several people in authority were hydrogen gas in our galaxy at 1420MHz. national interest. fi ercely opposed to the pro-European Because this radiation penetrates the Then a further diffi culty with the wire movement, and just as the acceptance dust clouds, it offered an important new mesh design arose. The mesh could only documents were fi nally about to be tool for understanding the galaxy. Hence be produced in strips a few feet wide, and dispatched to Siemens a call was received Lovell requested that Husband modify the no economical way could be devised to from the UK fi rm Brush, which had been mesh from 2 x 2 inches to 2 x 1in, at least make the thousands of electrical joints pressured into quoting a competitive price in the central portion of the refl ector out between the separate strips once they had against them. Metrovick was abandoned in to a radius of 50ft. The extra wind loading been installed in the dish. So the design acrimonious circumstances, Siemens was caused by this modifi cation meant that was changed once again to use solid steel

48 PRACTICAL WIRELESS January 2020

Jod Bank 2.indd 48 18/11/2019 08:04 Feature

sheets instead of open mesh for the whole refl ecting surface. The plates, which were about 3ft square, could be welded together in concentric rings, working outwards from the centre. Since there is no leakage through the solid refl ector, the gain at 10 144MHz was expected to be about 39dBi and the beamwidth less than 2°. conditions the structure was likely to suffer Photo 6: At the top of the towers the gearboxes In 1970 the refl ector was upgraded from the type of oscillatory resonance that behind the 50hp elevation motors drive the gun by constructing a new more accurate had destroyed the Tacoma Narrows Bridge turret racks connected to the refl ector bowl. solid-sheet surface above the original in the USA. To prevent this happening, it (Jodrell Bank) Photo 7: The displays in the bowl, which extended the frequency would be necessary to attach a huge ver- control desk indicated galactic latitude and range to 5GHz. The new surface was tical ‘bicycle wheel’ structure to opposite longitude, right ascension, declination, sidereal made shallower than the original so that edges of the dish, connecting it to damping time, actual and required azimuth and elevation the distance to the focus box is greater, wheels mounted on the diametrical girder. and universal time. (HB9ANY) Photo 8: The increasing the effective area illuminated Later this was replaced by a more robust Mark I antenna with the USAF/STL telemetry by the feed. Since the refl ector surface double wheel structure, which has a load- equipment in front of the control room at the added in 1970 had become badly bearing as well as a damping function. left of the picture. (Jodrell Bank) Photo 9: The corroded by 2000, it was replaced by 336 The effect of all the changes, combined steel lattice tower supports the focus box with new galvanised steel plates, set using a with the continually increasing prices of a cryogenic container housing the receivers. holographic profi ling technique that gives steel and labour, led to the estimated cost (University of Manchester) Photo 10: Laying new the best performance at 6GHz. They are of the antenna rising to £630,000. The pro- surface panels. (Jodrell Bank) painted white to refl ect the heat of the ject was now £260,000 in debt and in deep sun and prevent them from warping. In crisis. A committee of enquiry was set up almost daily contact with Lovell for fi ve heavy rain, the bowl can collect more than and the British press vehemently decried years, and for a consulting engineer to be 1000 litres of water per hour. It has big the waste of taxpayers’ money. This led accused of lack of cooperation with his drainpipes! to an investigation by the Public Accounts client would be disastrous for his compa- Committee (PAC), which based its report ny. He demanded that Lovell write a letter Crisis on the interrogation of the newly appoint- to The Times denying the allegations and By 1954 it became clear that the modifi ca- ed secretary of the DSIR, a distinguished threatened Lovell and the University with le- tions to the design of the dish were going professor of chemistry who had no direct gal action for damages. But such a refuta- to necessitate major changes to the sup- knowledge of the history of the project. tion was impossible, since the PAC report porting structure, increasing the weight of When the report was published it accused was a privileged document. Just as the steel required and leading to a huge over- Lovell of irresponsibility in using pub- huge antenna was approaching an opera- expenditure. In addition, wind tunnel tests lic funds, and Husband of making design tional state, it seemed that Lovell’s career of a model of the antenna by the National changes without consulting him. was over and he would be landed in prison. Physical Laboratory revealed that in gusty Husband was furious. He had been in But then a miracle happened.

Enter our competitions at www.radioenthusiast.co.uk/competitions

January 2020 PRACTICAL WIRELESS 49

Jod Bank 2.indd 49 18/11/2019 08:04 Feature

Photo 11: The Mark IA antenna has a new refl ector with reinforced steelwork and twin load- bearing circular girders. (HB9ANY) The Sputniks That miracle appeared unexpectedly on October 4th 1957, when amateurs around the world reported receiving the beeping from the 20MHz transmitter onboard Sputnik I, the earth’s fi rst artifi cial satellite, which had been launched without prior warning by the Soviet Union. The implication was clear. Soviet space technology was much in advance of the US Vanguard effort, and a carrier rocket that could launch a satellite could also deliver a military payload over an intercontinental range. Lovell was astonished to learn that there was no defence radar in the West that could track the rocket and he was asked to see if he could do so. A small 36MHz 150kW meteor research radar set was quickly hoisted to the small laboratory under the bowl of the new antenna and the rocket was located within 24 hours. Suddenly the eyes of the world were on Jodrell Bank, the control room was seething with reporters and cameramen, and the BBC had more engineers on site 11 than Lovell had on his staff! Three weeks later public enthusiasm was raised to even Able”. This gave away the fact that Lovell particles in interplanetary space. A high- greater heights with the launch of Sputnik had secretly been asked if he could track gain ground station antenna was required II carrying the dog Laika. Jodrell Bank duly the Pioneer rockets that the USAF would to communicate with the spacecraft, detected the carrier rocket at a range of a attempt to send to the moon using its Thor- since its low power transmitters had thousand miles and tracked it as it burned Able launch system. The rockets were omnidirectional onboard antennas. In up in the atmosphere a month later. unsuccessful as moon probes but Jodrell addition to receiving the telemetry on In spite of the public excitement and Bank tracked Pioneer 2 and recorded 378.2MHz, Jodrell Bank transmitted the acclaim, deadlock among the funding the scientifi c data that it transmitted on commands to the probe on 401.8MHz to authorities over the outstanding debt 108.06MHz as it travelled 71,100 miles into separate it from its Thor-Able launcher. The prevented the antenna being handed over space before falling back to earth. imagination of the public was captured to the University and Husband prepared Jodrell Bank received even more when the antenna received weak signals to serve Lovell with a writ for damages favourable publicity when it tracked the from the spacecraft out to 22.5m miles of £1m. The University informed Lovell more successful Soviet Luna 2 probe that from earth. that as long as the PAC record stood, they was launched in September 1959. Lovell A few days after this success Lovell would not be able to defend the case and received a telex from Moscow indicating received an unexpected telephone call, not without any means of paying he would be the rocket’s transmitter frequencies, from the media but from Lord Nuffi eld. imprisoned. coordinates and expected lunar impact “How much money is still owing on that It was not until July 1958 that the time, which allowed the antenna to track telescope of yours? I want to pay it off”. crisis was resolved, when the PAC was the probe down to the surface of the As Lovell started to thank him, he replied persuaded to issue a rebuttal of its original moon. The trajectory was confi rmed by “That’s all right, my boy, you haven’t done accusation and an additional grant of analysis of the doppler shift of the received too badly”. £130,000 was received from the DSIR. The 19.992MHz signals, dispelling the doubts Lovell’s long and bitter struggle was antenna was freed for use by the University expressed by some commentators that fi nally over. Ten years after its conception, but in spite of a successful public appeal the mission had succeeded. Shortly his dream had become reality and the a debt of £85,000 remained. It took further afterwards Jodrell Bank was once again debt had been cleared at last. It had been developments in the space race to save in the limelight when it received the a challenging, tortuous and hard-fought Jodrell Bank. signals from Luna 3 transmitting the fi rst adventure, but Lovell’s enthusiasm and photographic images of the far side of the tenacity had paid off and the world’s The Space Probes moon. largest steerable antenna was at last in July 1958 a large trailer was spotted The antenna also played a critical role free to pursue its mission of probing the approaching Jodrell Bank carrying a in the Pioneer 5 mission to explore the mysteries of the radio emission from the container marked “US Air Force, Project cosmic rays, magnetic fi elds and solar fl are heavens.

50 PRACTICAL WIRELESS January 2020

Jod Bank 2.indd 50 18/11/2019 08:04