UNIVERSITY OF CALIFORNIA AT LOS ANGELES REPORT OF WIRELESS TELEGRAPHY COMMISSION. Presented to Parliament by Command of His Majestij. LONDON : PRINTIiD AXD PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE. To be purchased through any Bookseller or directly from H.M. STATIONERY OFFICE at the following addresses; Imperial House, Kixgsway, Loxdox, W.C. 2, and 28, Abingdon Street, London, S.W.I; 37, Peter Street, Manchester; 1, St. Andrew's Crescent, Cardiff; 23, Forth Street, Edixburgh; OR FROM EASON & SON, Ltd., 40 & 41, Lower Sackville Streev, Dublin. 1922. [Cmd. 1572.] Price Is. Od. Xrt. REPORT OF WIRELESS TELEGRAPHY COMMISSION EXPLANATORY FOEEWOKD BY THE VICK-CHAIRMAN. 1. The severe!}' technical nature of this report requires that something in tlie nature of an explanatory sunimarv sheuld be attache' 1 to it. 2. The first section of the report gives the terms of reference of the Commission and also a recapitulation of the recommendations ot the Imperial Wireless Telegraphy Committee (1919-20), which the Commission were instructed to follow. The next sixteen para- graphs then deal in a broad way with the problen:s reg;i.rdin" masts antennae, machinery and appaiatus presented by the mstallation ()f thermionic valve plant on a scale larger than 'hitherto attempted and describe the solutions arrived at. Special attention is paid to the thermionic valve plant itself, to the ability of the industry to meet the probable demands, and to the question of capital "and maintenance costs. o. The visit of the Commission to the Marconi Company's station at Carnarvon is referred to. The conclusions drawn are, firstly, that the installation at tliat station is approaching the order 'of magnitude required in the Chain stations: and, secondly, that the Marconi Company is in a position to supply full size thermionic equipment for the Chain stations. Tl)e Carnarvon station has succeeded in communicating with Australia direct at certain hours of the day and therefore it is ceitain that the Chain station in England, which would be of three or four times the signalling strength of the Marconi station, could communicate with Australia throughout a longer diurnal period. 4. In later paragraphs (paragraph 20 d seq.) improved methods of reception and the general arrangements (jf the receiving stations are described. Under the heading" Sites "(paragraph 25) is^given an outline of the work which was undertaken by the Commissioli at the request of representatives of the Government of the Union of South Africa with the result of showing the advisability of erecting a new African terminal station near Johannesburg in preference to adapting the ex-German station at Windhuk. ^ 5. The second section of the report is a short portion headed '' General Recommendations." Paraphrased briefly these are to the efiect that — (1.) Thermionic valve stations should be erected in England, Canada, Australia, South Africa and India. A thermionic valve station should also be erected in Egypt to duplicate the arc station novv being completed by tiie British Post Office at Abu Zabal. At each of the other centres, namely East Africa, Singapore and Hong Kong an arc station should be erected with sjkace for the addition of thermionic valve plant later. (2.) Two wavelengths should be allocated to each transmitting station. 3 (3.) Each country should have one receiving centre (excepting '^.'"'A-. Canada) and that centre should be equipped for reception from several of the chain stations simultaneously. r- 6 The third section of the report consists of detailed technical recommendations. Under each country (excepting Canada) specifica- tions are given of the masts, machinery and buildings appropriate to the locality. These technical recommendations enihody a number of ^^ items of which mention should be made in this foreword : — \; England. >i 7. It is suggested that the Marconi Company be invited to -> tender for the supply of thermionic valve plant and associated •equipm.ent. ["Recommendation (11).] Canada. 8. It is recommended tliat a technical conference of Canadian >^' Oovernment representatives should be convened to discuss with the t> Commission special problems arising out of the geographical circumstances of (Janada. [Eecommendation (13).] Aust]:alia. ^ 9. Alternative designs are suggested, one of which could probably ^ be carried into effect almost entirely by industries already established ^ within tiie Commonwealth. [Eecommendation (14).J GC oc South Africa. 3 10. The plans suggested assume that the station is to be on the Eand near a bulk supply of electricity. In this event the capital cost would be smaller than that of the typical chain stations, ^ and, if desired, running machinery could be entirely dispensed with. '.. [Eeconnnendation (16).] ts India. 11. A station similar to that planned for England is sucjofested. o [Eecommendation (18).] E(tYPT. ^ 12. A single receiving centre for both the new valve station and ^ the arc station is proposed, and from this centre both stations would be controlled. Special receiving apparatus is proposed. [Eecom- mendation (19).] CD East Africa. 13. An arc station is proposed, drawing its electrical power from the falls of tlie Eiver Thika, with reservation of the water of the Chania for future extensions. [Recommendations (21) (22).] Singapore. 14. A station equipped with arc and machinery like Leafield, Oxfordshire, is planned, but with a different antenna. [Eecommen- dation (26).] Hong Kong. 15. A station resembling that at Singapore, but with a less costly antenna is proposed. [Eecommendation (30).] VTt. 2.5794/2 2.-)01 1/22 F.O.P. [7531] Gp. 3(i B 2 283532 o 10. The structural work and machinery at eacli station have been pUxnned with the endeavour of kee})inu the probable cost within the approximate estimates submitted by the Imperial A\'ireless Telegraphy Committee in their report. That is to say, the average cost "of the overseas stations will not exceed £100.000. exclusive of the cost of erecting residences for the staffs at some of the stations. The stations in England, Egypt, East Africa, Singapore and Hong Kong, for which the Imperial Government is presumably responsiWeTshould not exceed in the aggregate the sum of £85o,000" 17. The report terminates witli an appreciation of the help rendered to the Commission by the Admiralty, the War Office, the Air Ministry, the Post Ottice and the Department of Scientific and Industrial Kesearch, and with a similar tribute to individuals. 18. Looked at as a whole, the report provides specifications sufficiently full for the immediate preparation of estimates. A later report will give detailed specifications. All the stations ai-e planned to permit of easy extension of antenna, buildings and plant, 19. Finally it should be emphasised that during portions of each day much of the Impeiial strategic, official and news traffic could be carried on by direct communication l)etween any pair of principal centres, the intermediate stations being omitted : but the intermediate stations would be necessary for relay work during the less clear portions of the day, and also for handling their own local traffic. The news messages transmitted from the principal centres could be received at many stations in the Empire, for example in New Zealand, at the cost of an inexpensive addition to their existing receiving equipment. Foreign stations in many parts of the world would be able to pick up news and propaganda from one or other of the principal centres. Ikcembcr 9, 1921. W. H. ECCLES. To THE CaDINET. REPORT. 1. On the 2:.ird December, 1920, the Wireless Telegraphy Com- mission was summoned under the following letter of appointment : — The Cabinet have decided to appoint a Wireless Telegraphy Commission as follows : — The Kiglit Hon. Viscount Milner, Q^.G.Vj.,O.QM.(^. {Chair mem). W. H. Eccles, Esq., D.Sc, F.E.S. {Vicr-Cbairman). L. P.. Turner, Esq., M.A., M.I.E.E. E. H. Shaughnessy, Esq., O.B.E.. M.I.E.E. Lieutenant-Colonel C. 6. Crawley, K.M.A., M.I.E.E. {Secrcfari/). with the following terms of reference : — (i.) To decide upon the wireless plant most suitable for carrying out the scheme of Imperial wireless communications [7531] recoimueniled by the Imperial Wireless Telegraphy Ccjimnittee, bearino- in mind the necessity for the co-ordinati(jn of the Chain with existing telegraph services, and to design the necessary stations. (^ii.) To make recommendations regarding the actnal sites for the stations proposed by tlie Imperial Wireless Telegraphy Committee. (iii.) To advise generally iipon the preparation of specifications for machinery and apparatus, the making i this loss can be avoided and an approach to the ideal attained by making the mast or tower in sections with insulating portions and standing tlie mast on an insulating base. By varying the dimensions of the insulating portions a close approach to the ideal may be made. There are some mechanical difficulties in this mode of construction, and the consideration of these details will fall within the purview of the constructing authorities, assi.sted by the Conniii.ssion a« necessary. Tliey do not gieatly affect tlie capital cost, and may he regarded as subsidiary detaih The above remarks apply alike to self-supporting towers and to masts supported liy guys, the guys also being segmented l)y insulators in the latter case. The cost of masts is much less than tliat of towers. Earth Screens. 17. The higl) frequency currents in an antenna are accompanied by similar currents in the earth under the antenna, unless the earth is screened by a suitable grid of copper wires. Such earth currents cause great loss of electrical energy. In the case of the thermionic transmitter, it is especially necessary to reduce this loss, and therefore the utilisation of efficient earth screens at all the Chain stations is advised. Poiviv Supply and Electrical Machinery. 18. The electrical machinery needed for the supply of energy to a large thermionic set presents no difficulty and "need not be discussed here. Emerycncy Jieceiriny Gear and Operating A^rparatus. 19. In the event of breakdown or interruption of tlie telegraph lines connecting the transmitting and receiving centres of a duplex station tlie whole traffic must be conducted Ijy simplex operation from the tra,nsmitting station. It it therefore necessary to instal at each ti-ansmitting station an emergency set y various forms of directive a])paratn8. 22. The Imperial Wireless Telegraphy Committee recommended that each station of the Chain should be one-way duplex, but it would seem that better use of the plant could be made if each station were provided with as many receiving posts as there are stations with which it will communicate; and, further, that eacli of the Egyptian stations should be assumed to communicate with l)oth East Africa and India. Such an arrangement is quite feasible and offers the following advantages : — (1.) Until the routes are fully loaded it allows of improved working during periods when tlie How of traffic in one direction is greater than in the other direction. (2.) During periods when bad atmosplieric conditions prevail at one station and not at the adjacent stations the one station can be sending to either of the others, and when the good reception period at the one station ctunes the time lost can to some extent be made up by receiving from idl adjacent stations at once. 23. For economy of statting and for traffic reasons it is highly desirable that all the receiving posts of one station shall be situated together. At each of the non-terminal stations, therefore (Egyi)t, East Africa, India, Singaj)(ne), the receiving posts sliould 1)6 grouped together at one spot, distant 20 to 40 mih^s from the transmitting station In Egypt, Kast Africa and India, where the routes diverge through much less than a right angle, the line joining the trans- mitting site to the receiving site should be approximately per])endicular to the average direction of the signalling routes at the station ; but at Singapore, where the branch to Hong Kong is nearly perpendicular to the average India-Singapore-Australia route, the receiving site should Ite situated approximately on the line joining- Singapore to Hong Kong. In South Africa and Hong Kong the receiving site should preferably be situated 20 to 40 miles from the transmitting site approximately on the signalling route. In England the receiving post of the new station sliould preferably be placed with the existing receiving post at Banbury. In general the receiving site should be chosen so as to comprise a central plot, 250 yards by 50 yards for the operating building, and two other plots, 220 yards square, each suitable for containing a mast 300 feet high, about 550 yards from the central plot and on opposite sides of it. The general direction of the thi'ee plots should lie along the average dii'cction of the signalling route. 24. E.xperience recently gained in England and Egypt has shown that atmospheric interference may be markedly leduceil by each of three distinct methods, which may be referred to as — (a.) Atmospheric balancing. (&.) Limiting, (c.) Barraging. Designs are in progress for applying all these simultaneously in Egypt. If the benefits obtainal)le justify the expeiuliture, the other stations of the Chain can be similarly equipped in due course. 11 Sites. 25. The Admiralty have lent to the Commission the services of two officers who are now in Egypt on their way to East Africa and probably to South Africa, taking with them apparatus for making a radio- telegraphic survey, and instructed as to the other requirements the sites must fulfil and the data to be collected. '1 hey will probably visit Singapore and Hong Kong. At the invitation of the Indian Government, an engineer from the Post Office will visit India in connection with receiving tests organised by the Indian G(-ivernment, and will place his services at the disposal of that Government in respect of the choice of a site, if desired. 26. It should be remarked that a considerable amount of information regarding possible sites in East Africa. Singapore and Hong Kong has been collected by previous expeditions in connection with the old Imperial Chain proposals, and has been placed in the hands of the Commission. 27. The Imperial Wireless Telegruphy Committee recommended (1920) the use of the ex-German Windhuk station as the South African terminal station of the Chain, being under the impression that Windhuk was adequately connected liy land lines with the poUtical and commercial centres of the Union. Later information put Itefore the Commission by representatives of the linion Govern- ment Jias shown that new land lines wouhl be required, and that the maintenance of these lines would be costly. Under these circumstances, the Commission, at t!ie request of the representati\es of the Government of the Union of South Africa attending tlie Imperial Conference, drew up a memorandum upon the possilnlity of erecting an entirely new station near Johannesburg as the terminal station of the African chain. The capital outlay would be greater than that needed fur the adaptation of Windhuk, but the cost of maintenance would be less, nmcli retransmission of messages would lie avoided and better conditions for the staff' could be piovided. A radio- telegraphic survey of the region by aid of portable receiving apparatus will decide whether Johannesburg is sufficiently free from atmospheric electrical disturbance to ])e a suitable site. B^nldingfy. 28. The advantages of a symmetrical antenna have been referred to in paragraph 15. In order to ensure synanetry the buildings for housing the transmitting plant should be plficed at the centre of the transmitting site. In general, there will be a boiler house, an engine room and a higli frequency room, together with workshops and an emergency operating room ; but when power can be drawn from an outside supply the boiler house is not required. In view of the recommendations of the Imperial Wireless Telegraphy Committee it is important to plan the buildings in such a way that the l)oiler house, engine room and high frequency room can each l:)e extended easily. The form adopted in this Report is a very economical one : it consists of two or three equal bays, as the case may be, in parallel formation, with panelled ends, each lighted from the roof, which may l»e of saw- tooth type. The buildings may be oriented in any direction appropriate to the locality. The dimensions shown on the appended diagrams 12 of the English station must be altered to suit the climatic conditions of'eaeh country. The huildings for housing the receiving apparatus call for no special remark. They should follow generally the lines indicated on the diagrams of the English receiving buildings, but should be altered in dimensions to suit local conditions and to provide for the recommended number of route circuits. (4EXEKAL REC( )MMENJ)AT10XS. The (.'ommission recommend that — (1.) The transmitting stations in England, (Janada, Australia, the Union of South Africa, India and Egy})t be equippetl with thermionic valve plant in the manner described in detail bidow. But in view of the amount of skilled attention demanded by this plant in its present stage of development an't having regard to the isolated nature of the stations in East Africa, Singapoi'e and Hong Kong, these three stations shouhl be equipped for comljined arc- valve transmission : the arcs alone should be installed immediately and the thermionic valve plant sliould be added after practice has become standardised. (2.) Each transmitting station should be capable of working with either of two wavelengths as may be appropriate to the time of day and the atmospheric conditions. (3.) Each receiving centre should be provided with antennae and apparatus sufficient for working simultaneously with the other stations normally communicating with it, and all the receiving and operating apparatus should be in one and the same building. DETAILED TECHNICAL EECOMMENDATIONS. England. Transmitt ing Station, (4.) Mas/s. — The masts should be of steel, each 250 metres high, guyed three ways with six concrete anchorages, both masts and guys insulated in sections, and designed to take a horizontal pull of 10 tons at the top and a wind toad of 60 lb. per square foot with a factor of safety of 3. Four masts should be erected, one at each corner of a square not exceeding 400 metres side. The site should allow of extension of the antenna by the addition of two masts at each end, and the whole area available should therefore be about 1 mile by ^ mile. (5.) Antenna. — Tlie antenna should be designed so as to reduce corona to a minimum, and should be especially highly insulated. Its electrical cajjacity should be about one-fortieth of a microfarad. (6.) Harfh Srrcen. — The earth screen should be a series of copper wires radiating from the centre of the site to its edges, and sujjported at not less than 8 feet from the ground by insulators. (7.) Aatcmia Tuniuff Coil. — Tlie tuning coil should be designed for an antenna current of 500 amperes, provided with tappings for tuning the antenna to wavelengths between o,000 metres and 16,000 metres. Tla- high freiiueucy re.sistance of the part in use should not exceed one-third of an ohm at the eorrespondinj^- fre([uency. (8.) Thermionic Valvr Set (provided in duplicate).— A thermionic valve set capahle of delivering at least 120 kilowatts of high- frequency power to the antenna, with the necessary connections to the antenna coil, with control gear and protective devices in the anode and filament circuits, with grid leaks and condensers, relay and hand keys, air-piping for valves and keys, compressor and instruments, all connected up. The set should l)e capable of .snb-division in stages so that a convenient fraction of the total power may be taken to the antenna at will. It should also be capable of extension until 240 kilowatts can be delivered to the antenna. Current may be supplied either from high voltage D.C, machines (10,000-12,000 volts) or by rectifying alternating current; tenders will show which is preferable from the point of view of economy. The set should be guaranteed vvith respect to constancy of wave- length, purity of wave, overall efficiency at each wavelength and average cost of renewals. It must be capable of transmitting con- tinuously at hand speed and at ninety words per minute at full power for reception at 2,500 miles. It is suggested that the Marconi Company be invited to tender for the apparatus recommended under the headings " Earth Screen," " Antenna Tuning Coil " and " Thermionic ^'alve Set." If their quota- tion should not l»e acceptal)le, thermionic plant, &c., could be designed by the Commission after the conclusion of the work now being under- taken at Horsea, erected in England, tested, and proved designs recommended to the Dominions and to India. (9.) Power Sapplif and Electrical Machinerij. — -For the generation of the electrical power supply water- tube boilers, burning oil or coal, should be used. The requirements are : — Thi'ee water-tube boilers, each evaporating 7,000 lb., or two eacli evaporating 10,000 lb., of water per hour, with superheaters and economisers, pipe work, water softeners, feed-pump, together with condensers and cooling, plant. *Two 2oO-kilowatt turbo alternators, three-phase, 50 cycles, 3,000 volts lietween phases. *Two 250-kilowatt tliree-phase transformers, giving 15,000 volts. Two turbines, each driving one 50-kilowatt 1).C. machine, 220 volts, arid *one oO-kilowatt D.C. machine, 20 volts. High and low tension switch gear. The alternative mentioned in Recommendation (8) would require the sul)stitution of tlie following two items for the three items marked with an asterisk : — Two 2U0-kilowatc steam-driven sets giving 10,000 to 12,000 volts D.C. Two 20-kilowatt sets giving 20 volts D.C. Later extensions would be one boiler, one turbo alternator (or one 200-kilowatt 10,000-12,000 volts D.C. set), one transformer, one 20-kilowatt 20 volts D.C. set, one D.C. turbo generator, switch gear, &c. u (10.) B}'ihUiujs. — Tlie traiisiiiitting station buildings should be at the centre of the site. They comprise the sections mentioned in paragraph 28. A travelling crane is required in the boiler-house and the engine-room. Diagrams showing the dimensions are appended. (11.) Emcnjencji Fucciving (rear tind Operatin;/ Ajrpuratus. — The emergency arrangements should comprise a small aerial, a receiving set of the Post Office pattern, perforators, automatic trans- mitters and recording apparatus. Meccivino Station for Daplcx, (12.) The receiving station sliould be situated at Banbury, and provided with two sets of apparatus similar to that being installed at Banbury for the Learield-Abu Zaljal link of the Chain, but supple- mented by limiting apparatus. Details appear in paragraph 23. As soon as Canada enters the Chain scheme an additional aerial system and .set of receiving appai-atus will be needed. Telegrapli lines in duplicate connecting Banbury to the trans- mitting station will be required. Can.-vda. (13.) Should the Canadian Government decide to have stations at Moritreal and Vancouver, the former could maintain a good service with the station in England and the latter would be able to commu- nicate during part of the day with England and with Australia. Both stations -might be as descrilieil in Kecommendations (4) to (12). The Commission would be happy to confer on technical details with the Canadian authorities. A conference should be convened at an early date. Australia. (14.) The transmitting station should be as described in Eecom- mendations (4) to (11), unless an ample public supply of electricity is available. In this latter event the transmitting station might be similar to that described in Becommendation (16). (15.) The receiving station should have two aerial systems and three sets of receiving apparatus, with accommodation for a third outfit for direct communication with South Africa when desired. The aerial for this receiving station consists of a pair of horizontal wires each about 250 feet long supported upon two 75-feet poles. The site required is as indicated in paragraph 23 and the buildings are as intlicated in the appended diagrams. When a station is built in Vancouver additional receiving equipment will be required. Apart from this, additional receiving equipment will be necessary if the Chain station is required to work across the continent of Australia. A 12-kilowatt D.C. supply (public or oil engine) will be required for lighting, charging batteries, and running telegraphic apparatus. Telegraph lines in duplicate connecting the transmitting station to the receiving station will be required. The Commission have been informed that the Australian (Govern- ment prefer to have the Chain station situated at Perth rather than at Port Darwin. 15 South Africa. Tra nsiuittiitg Statiuii. (1*3.) If the transmitting station is placed near Johannesburg the masts, the anteinia, the earth screen, the tuning coil, the thermionic valve set and the emergency gear should be as described in Piecommendations (4) to 8)ancl (ll). Tlie power supply and electric macliinery should be — *Two 250-kilo\vatt three-phase transformers, 15,000 volts. *Two :*)0-kilo\vatt three-phase transformers, 20 volts. Two lO-kilowatt lighiing transformers, 220 volts. Two transformers supplying- two 4U-kilowatt rotary converters giving 220 volts D.L". High and low tension switch gear. Overhead transmission lines in duplicate. Later extensions would lie one single set of transformers and gear as scheduled. The alternative mentioned in llecommendation (8) would require the substitution of the following two items for the two items marked with an asterisk : — Two 200-kilowatt motor generators, 10.000 to 12,000 volts D.C. Two 20-kilowatt three-phase transformers, 20 volts. U\ each of the abova schedules a meicury rectifier may be substituted tor each rotary converter. The buildings of the transmitting station should l)e planned with two bays in parallel formation on the lines indicated in paragraph 28. Beeeicing Station. (17.) The receiving station should have one aerial system and two sets of receiving apparatus in the first instance with accommodation for a second outHt for direct communication with Australia when desired. The nature of the buildings is indicated in the attached diagrams, and of the site in paragraph 28. A 12-kilowatt D.C. supply (public or oil engine) will be required for lighting, charging batteries and running telegraphic apparatus. Telegraph lines in duplicate connecting the receiving station to the transmitting station will be recpiired. India. (18.) The transnntting station should be as described in Recom- mendations (4) to (11). The receiving station should have four aerials and five receiving sets. Site and buildings should be as described in paragraph 23 and in the appended diagrams. A 12-kilowatt D.C. supply (public or oil engine) will be required for lighting, charging batteries and running telegraphic apparatus. Telegvajjh lines in duplicate connecting the receiving station to the transmitting station will be required. Egypt. (19.) The transmitting station, ujdess ]'laced at Abu Zabal, should be of the type described in Kecommendations (4) to (11). 16 Tlie receiving station should luive four aerial systems and five sets of receiving- a])paratus. The site should consist of a central plot 200 yards by 50 yards, containing the operating building, &c., and two other plots 220 yards square, each containing a oOO feet mast 550 yards away in opposite directions from the central plot. The three plots should be connected l)y cable. A 12-kilo\vatt D.C. supply (puldic or oil engine) will be re(iuired for lighting, charging batteries and running telegraphic apparatus. Telegraph lines in duplicate to Abu Zabal and to the new transmitting station will be required for the purpose of remote control of both stations. East Africa. TransmiUijuj Stafion . (20.) The masts, antenna', earth screen, tuning coil and emergency gear should be as (lescril)ed in Recommendations (4) to (7) and (11). (21.) Arc Converter. — Two 250-kilovvatt arcs sliould be installed, each provided with chokes, condensers, contactors, resistances, instru- ments, keying inductances, keys and auxiliaries, similar to those at Leafield. (22.) Power Suppli/ cud Electriral Machmcrji. — The hydroelectric project at Thika, reported upon by the Public Works Department, Nairobi, on HOth Marcli, lOli, should be carried into effect, at least in part, if, as seems probable, the wireless transmitting site can be near the falls. For the purposes of the wireless station the water of the Thika is sufficient, and the proposed siumltaneous utilisation of the Chania might therefore be reserved for any eventual enlargement of the wireless station. The electrical machinery should consist of : — Two 250-kilowatt water turbine-dynamo D.O. sets, delivering 350 amperes, with voltage regulation between 500 and 1,000 volts. Two 60-kilowatt water turbine-dynamo D.C. sets, 220 volts. Switch gear. Two overhead transmission lines from the hydroelectric house to the wireless transmitting station. (23.) Should the hydroelectric project be for any reason im- practicable, the electrical supply should be generated by steam, as described in Recommendation (27). (24.) Binldings. — A hydroelectric building should be provided at Thika River. The transmitting station buildings should be as indicated in the diagrams appended. Residences for a staff of approximately six whites and twenty others should be provided. The receiving buildings should be as shown in the appended diagrams, and, in addition, residences for the operating staff should be provided. Beceiving Station. (25.) The receiving station should have three aerial systems and four receiving sets, with accommodation for the addition of a fourth outfit for direct communication with England should this prove desirable. 17 The site should be so chosen as to permit of the erection of a pole line 250 yards long across the central plot, but otherwise con- formino- to the description in paragraph 23. A i2-kilowalt D.C. supply (public or oil-engine) will be required for lighting, charging batteiies and running telegraphic apparatus. Telegraph lines in duplicate connecting the receiving station to the transmitting station will l)e required. Singapore. TnaisviitHng Station . (26.) The masts, antenna, earth screen, tuning coil and emergency gear should be as described in liecommendations (4) to (7) and (11). The arc equipment should be as described hi Kecommenda- tion(21). (27.) Power Snpplji and Electrical. Machinery — Three boilers, each evaporating 7,000 lb., or two each evaporating 10,000 lb. of water per hour, with superheaters, economisers, water softeners, feed pump, together with condensers and cooling plant. Two 250-kilo\vatt reciprocating-engine and dynamo sets, 350 amperes D.C, with voltage regulation between 500 and 1,0 UO volts. Two 60-kilowatt reciprocating-engine and dynamo sets, 220 volts D.(J. Switch gear. (28.) The buildings at the transmitting station should be as indicated in the appended diagrams. llesidences should be erected if necessaiy, for a staff of six whites and thirty-two others. At the receiving station the buildings should be as indicated in the diagrams, and residences may also be necessary for the operating staflf. Receiving Station. (29.) The receiving station should have three aerial systems and four sets of receiving apparatus. The site should be 250 yards by 50 yards with facilities for a pole line 250 yards long running across it, and conform to paragraph 23. A 12-kilowatt D.C. supply (public or oil engine) will be required for lighting, charging V)atteries and running telegraphic apparatus. Telegraph lines in duplicate connecting the receiving station to the transmitting station will be required. Hong Kong. Transm itt iny Station . (30.) The masts should be of steel, 200 metres iiigh, guyed three ways with six concrete anchorages, both masts and guys insulated in sections, and designed to take a horizontal pull of 10 tons at the top and a wind load of 60 lb. per square foot, with a factor of safety of three. Four masts should be erected, one at each corner of a square not exceeding 400 metres side. [75311 C 18 The site should allow of extension of the antenna ))y the addition of two masts at each end, and therefore the whole area available should be about 1 mile by half a mile. The antenna, earth screen, tuninif coil, and emergency gear should be SIS described in Recommendations (5; to (7) and (11). The arc equipment sliould be as described in Recommendation (21). The power supply and electrical machinery should be as descriV)ed in Recommendation (27). The buildings should be as described in Recommendation (28). Rcceiviiiji Station. (.31.) The receiving station should be generally the same as that descril)ed in Recommendation (17). The Conanission desire to place on record tlieir cordial thanks for the helpful co-operation unsparingly given by the Admiralty, the War Office, the Air Ministry, the Post ( Jttice and the Radio Research Board of the 1 )epartment of Scientific and Industrial Research during the past twelve nu)nths. All these Departments have placed at the disposal of the Commission their technical records, their accumulated experience, and material facilities for undertaking practical trials of methods and apparatus. The Admiralty, the War Office and the Post Office have lent officers for work at home and abroad besides constructing special trial sets of apparatus at the request of the Commission. Without this assistance tlie work of the Commission would have been greatly protracted. The Commission also desire to express their great appreciation of the valuable aid atfoided by Colonel Sir S. H. Wilson, K.B.E., C.H., C.M.G., Principal Assistant Secretary to the Conanittee of Imperial Defence, by keeping them in touch with all the Departments of State consulted by the Commission upon matters relating to the Imperial wireless chain. The Commission is especially grateful to Lieutenant-Colonel C. G. Crawley, R.M.A., Secretary to tlie Conanission, who has carried out his work with very great efiieiencv. W. H. ECCLES. E. H. .SHAUGHNESSY. L. B. TURNER. C. G. Crawley, Secretary. 2, Whitehall Gardrm, S. W. 1, December 5, 1921. to' >! o| inj SGA0Z2 NOIid333y T" < >3 UJ o V — •; 5^ < ex.- - sq'a OS U- o < h- UJ Q CC O Ll_ C/5 Q > O in CM J _ __ < z u o Ll_ I- o to UJ L o ji/o/^c/pjjyT J.O aui-j: spA 05 -H ^ ^iU ISVIAI ^ \P;£A Qi UJ u cn oo Q-x ''V~ .i^ ^. i ISVMI p .- ._£_ t^ cjS CO o 1— ^ f: --1 1 '^ o CO K. ui ^ C flJ r- S CO u: o «?.5q. ^s Suj Vt) !■ Jl_ BOILER HOUSE ENGINE & CONDENSER ROOM WIRELESS ROOM k 34'0- -> * 34- > PLAN. 34-0 ■^ OPERATING ROOM _^_ STORE WORKSHOP "F .1 "6 "5 1^ ,30 - 35' O ,!« 25 0- Boiler House ivill be 36 feet wide if Coel is used. Buildings to be modified according to local & climetic conditions *35. 2£ liH.Z . 2500 I. i'^. FOR IMPERIAL STATIONS ROUGH DIMENSIONS OF TRANSMiniNG BUILDINGS. Wireless Section E-ii) C':. Office GFO. London. t.C WTC.20 De<.. lOZI. MaJbyASonslith. OsJ O ■Cj.'u ~~- III s i5 . Second Report of wireless Telegraphy Commission Prese?ited to Farl'wmejit by Command of His Majesty LONDON : PRINTED AND PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE To be purchased directly from H.M. STATIONERY OFFICE at the following addresses ; Adastral House, Kingsway, London, W.C.2 ; 120, George Street, Edinburgh j York Street, Manchester; i, St. Andrew's Crescent, Cardiff; I 5, Donegall Square West, Belfast \ or through any Bookseller. Cmd. 2781 1926 Price 2d. Net REPORT. To THE Cabinet, 1. On the 23rd December, 1920, the Wireless Telegraphy Commission was summoned under the following letter of appoint- ment : — The Cabinet have decided to appoint a Wireless Telegraphy Commission as follows : — The Eight Hon. Viscount Milner, G.C.B.. G.C.M.G. (Chairman). W. H. Eccles, Esq., D.Sc, F.R.S. [Vice-Chairman). L. B. Turner, Esq.. M.A., M.I.E.E., E. H. Shaughnessy. Esq.. O.B.E., M.T.E.E.. Lieutenant-Colonel C. G. Crawley, E.M.A.. M.I.R.E. (Secretary), with the following terms of reference : — (i.) To decide upon the wireless plant most suitable for carrying out the scheme of Imperial wireless comnmni- cations recommended by the Imperial Wireless Telegraphy Committee, bearing in mind the necessity for the co-ordination of the Chain with existing telegraph services, and to design the necessary stations. (ii.) To make recommendations regarding the actual sites for the stations proposed by the Imperial Wireless Telegraphy Committee. (iii.) To advise generally upon the preparation of specifications for machinery and apparatus, the making of contracts and the construction of the stations. 2. A first report was submitted to the Cabinet on the 5th December. 1921, and was printed as Command Paper No. 1572. It contained plans for the erection in England of a wireless station having eight masts 820 feet high on a site 1 mile long by } mile wide, and equipped with power plant of 000 kiloM^atts capacity with a reserve of 300 kilowatts. The report also contained general specifications for stations of about half that size suitable for erection at other points of the Empire as recommended by the Imperial Wireless Telegraphy Committee, 1920. 3. During the year 1922 the Commission was consulted by the Governments of Canada, Australia, New Zealand, South Africa and India, and collected information about the radio-telegraphic features of various Empire sites. Meanwhile, as the proposed stations were the first of their kind and size, practical trials of designs were inaugurated by the Commissioners and carried out in collaboration with the Admiralty and the Post Office engineers. Many large-scale tests were undertaken in the wireless stations already operated by the Post Office. The Commissioners also made a detailed study of newly-constructed large wireless stations in America, France, Italy, Holland and Germany. 4. ill February 1923 the Cabinet decided to proceed with the construction of a powerful station in England pending the result of the discussions regarding the proposed stations in the Dominions and India, and Mr. Amery, in his capacit}' as Chairman of the Imperial Communications Committee, requested the Admiralty, War Office and Air Ministry to send each a representative to the Commission to advise on the needs of the Services as regards the range and situation of the English station and to help in deciding the power and type of the station. The Commission with the Service representatives concluded unanimously that the station should have twelve or sixteen steel masts each 800 feet high, and that the prime movers should have a capacity of 1,000 kilowatts for delivering 500 kilowatts to tho antenna. A site near Rugby was agreed to be the best of those available. It was decided that the wavelength should not be greater than 20.000 metres. The use of water-cooled thermionic valves was approved. 5. In accordance with the recommendation of the Imperial Communications Committee, the original Commissioners were to be held solely responsible for all plans and calculations and for all advisory work during the construction of the Rugby station. They therefore determined the general design of the station, and at their instruction all detailed plans and specifications were prepared by the Wireless Section of the Post Office Engineering Department to meet their requirements. This involved the preparation of 559 drawings and 109 specifications. These drawings and specifications were examined and approved by the Commission and the principal tenders obtained were scrutinised before contracts were placed. The buildings were erected by the Office of Works and the whole of the plant was installed by the Wireless Section of the Post Office Engineering Department in close co-operation with the Commission. 6. In April 1924 the Vice-Chairman represented the Commission at the meetings of the Cabinet Committee appointed to expedite the arrangements for wireless communication with the Dominions. The result of these meetings was that an indenture was made on the 28th July, 1924, between the Postmaster-General and Marconi's Wireless Telegraph Company for the construction of wireless beam stations for sending and receiving telegrams between England and Canada, with possible extensions giving similar duplex communication with Austraha, South Africa and India. The stations are guaranteed to give daily average communication of 18 hours with Canada, 12 hours with India, 11 hours with South Africa and 7 hours with Australia. In each of these countries the work on corresponding stations is well advanced. 7. The site for the Rugby station is about 900 acres in extent and is situated at Hillmorton, about 4 miles south-east of Rugby. The land is approximately 340 feet above sea level, and the maximum variation in level on the site is 30 feet. The site was chosen to accommodate sixteen masts each 820 feet high placed ^ mile apart. For reasons of economy it was decided to erect Wt. 13366/4364 10/26 F.O.P. [15124] 1000 12/26 [15558] only twelve masts in the first instance. Each mast contains about 200 tons of steel and is designed to withstand a high wind pressure with an adequate factor of safety and also to support an aerial which exerts a horizontal pull of 10 tons at the top of the mast. 8. The aerial is constructed in two sections consisting of one large octagonal cage aerial 2 miles long supported on eight masts and another shorter cage aerial 1^ miles long supported on six masts, two of the masts being used in common by both sections of the aerial. In all, about 27 miles of copper cable are used in forming the aerial. The airangement is such that the two sections can be connected together inside the station buildings to form one large aei-ial for extreme power, or can be used separately for two transmissions on high power. The earth system consists of an open network containing about 120 miles of copper wire buried a few inches in the ground and occupying a space about 1,600 feet wide under the whole length of the aerial. 9. The station buildings are situated at about the centre of the site and comprise a machinery hall 185 feet long by 47 feet wide by 32 feet high for housing the power plant, and a three-storey building 103 feet long by 42 feet wide by 60 feet high for housing the wireless plant. The power is obtained from a public supply Company, and the power plant installed at the wireless station is capable of converting about 1,800 kilowatts into power suitable for use in the wireless plant. The power is taken by cables from the machinery hall to the wireless building. The high-frequency generator is of the water-cooled valve type. It consists of two exciting units in duplicate and a main power amplifier. The latter consists of five similar power valve panels, each panel containing eighteen valves and capable of giving a high-frequency output of 180 kilowatts at a frequency of 16,000 cycles per second. By using three panels a total output capacity of about 500 kilowatts is available for use on the whole aerial, leaving two panels in reserve. Alternatively, the two sections of the aerial, each working with two power panels, can deal w^th about 300 kilowatts and 200 kilowatts respectively, leaving one power panel in reserve. Two primary oscillating circuits are j)rovided, one to deal with full power and the full aerial, and the other to deal with smaller power and the smaller section of the aerial. Up to the present the smaller section of the aerial has been reserved for use with an experimental telephony transmitter, and good and reliable two-day conversation across the Atlantic to New York has been obtained repeatedly for many hours of the day. 10. The telegraphy installation has, up to the present date, only been worked on the eight-mast aerial and with about two-thirds power. Even so, the signals have been heard all over the globe. A summary of the reports on the signals received at different distant places is appended. Further experience during bad atmospheric periods will determine to what extent, if any, it will be necessary to extend the aerial by the erection of additional masts. 11. With a view^ to the most economical and efficient utilisation of the whole of the plant at the station the lay-out was designed to provide for simultaneous use of two transmitters during the most favourable atmospheric periods. Experiments will shortly be made on the main telegraph transmitter and the transatlantic telephony transmitter to determine whether simultaneous operation is feasible. 12. In addition to the main telegraph transmitter and the transatlantic telephony transmitter, further installations are in contemplation, namely, a short-wave plarit and a medium-wave plant, utilising the existing masts for supporting the additional aerials. The development of this multi-way working of the Eugby station can be confidently left in the hands of the Post Office Wireless Engineers. 13. The Commission desires to place on record its cordial thanks for the helpful co-operation unsparingly given b}' the Admiralty, the War Office, the Air Ministry, the Post Office and the Piadio Research Board of the Department of Scientific and Industrial Research. All these Departments have placed at the disposal of the Commission their technical records, their accumulated experience and material faciHties for undertaking practical trials of methods and apparatus. The Commission wishes also to express its deep appreciation of the valuable services rendered by Lieutenant-Colonel Crawley, who has acted as Secretary to the Commission from the beginning of its work. W. MITCHELL-THOMSON. W. H. ECCLES. E. H. SHAUGHNESSY. L. B. TURNER. C. G. Crawley. Secretary. Whitehall Gardens, S.W.I, July 7, 1926. APPENDIX I. Early Kei'Okts keceived from various Stations during the Testing of the Pugrv Station, December 1925. (These reports are not selected but are given in order of date.) Date. Position. Remarks. Dec. 10 OffSicilv Signals good and clear. 11 Halifax' Ten times stronger than Leatield. Copyable, New York, 7") words per minute. Soutli Atlantic Signals very clear and very strong. Bugby easily readable above heavy atmospherics and jamming. Leafield has a dead area between Lat. 3 S. and 3' N. Rugby not affected in this area. Pretoria Note very good throughout. Cape Town Note good and steady. Suez Good and clear. Bordeaux siyuaLs much stronger than Rugby. Signals two or three times as strong as Leatield. Off Aden Very good and strong. Rugby effectively drowns all interference. Mataro Note clear and steady. Bermuda Note distinct. n • • • Note clear and musical. 12 Off Newfoundland . . . Signals thnndei'ing in. Newfoundland Signals fine and .steady. South Atlantic Note good. Caribbean Sea Dots indistinct, but improve later. Australia (resu Its at Note remains constant throughout, signals various centres) excellent. Off Cape Town Signals and note good. 14 China Station (from All .ships report note good, clear and steady. Couimander-in -Chief) Halifax Continuous heavy atmospherics, Rugby easily riding above. Newfoundland Fine note, but weaker than on 12tli. Mid-Atlantic... Note good and steady. Sydney Rugby was only high power European station readable through atmospherics. Good strength and note remained constant throughout. 15 Off Nantucket Atmospherics extremely bad. Rugby signals uuaffected, good note. Hong Kong ... Night telegrams apj^ear to have mtu-e solid note. 16 New York Rugby's signals readable through heavy atmospherics and jamming. 19 South Atlantic All telegrams received, strength 7-9. )i )? Spacing and Moi'se bad during noon telegrams on Dec. 14. 23 Hong Kong Commodore) (from All ships report note good, clear and steady. 29 Aden Note clear and steady. 31 Port Natal ... Strength excellent and easily readable above jamming. Bandoring (Jav a) ... Key action excellent. Frequency very con- stant. Dutch East Indies ... Rugby splendidly received, far ruore distinct than any other European station. APPENDIX II. SUMMAKY OF KePORTS FROM ShIPS EQUIPPED WITH STANDARD MARINE llECEiviNG Apparatus. (By courtesy of the Marconi International Marine Communication Company.) Some of these reports are based on the log of a single voyage. All the observations relate to the first few months of this year — a period when atmospheric conditions in tlie southern hemisphere are at their worst. In the columns headed " Strength " the figure 1 indicateb* tliafc signals are just aiulible, and the figure 6 indicates that the signals are the strongest required in practice. Locality. Day Transmissions. Night Transmissions. Interference. ATLANTIC OCEAN— Strength. Strength. Lat. 60-50 deg. North ... 6 to 9 7 to 9 Considerable jamming by European stations. .50-40 6 to 9 7 to 9 40-80 7 6 to 8 30-20 4 to 8 5 to 8 20-10 3 to 8 5 to 8 10- 4 to 6 6 Eastern Atlantic ... 7 to 9 7 to 9 Considerable janmiing by Bordeaux. Nortli -Western Atlantic .. 6 to 7 6 to 9 (Considerable jamminji by American stations. West Indies 3 to 7 5 to 7 Some jamming by American stations. Gulf of Mexico 3 to 5 5 to 7 Equatorial Atlantic 4 10 6 6 Lat. 0-10 deg. South 5 H 10-20 5 to i'J 3 to 7 20-30 5 to 6 4 to 6 30-40 4 to 5 4 to U Central South Atlantir- .. 5 5 Oii' Brazil I to (5 3 to 6 More easily copied day than night owing to atmospherics. Off Patagonia 1 4 Unreadable during day through inter- ference. Off South Africa 4 to 5 6 to 7 .\tmosplierics bad, especially during day. MEDITERRANEAN 4 6 to 8 Some jamming by European stations. RED SEA 5 7 Ditto. PERSIAN GULF o to () 7 to 8 Ditto. INDIAN OCEAN— Arabian Sea 5 to (3 7 to 8 Bay of Bengal 4 to t; 6 Eciuator 5 6 to 7 Niglit transmission better tlian day owing to disturbance. Lat. 0-10 deg. South .. 5 6 to 7 10-20 4 to 5 5 to 6 20-30 2 to 5 4 to 8 Central Area 3 to 5 7 to 8 South-West«rn Area 4 Oto 7 Off Soiitli Africa 1 to 5 5 to 7 Atmospherics very bad. PACIFIC OCEAN— Nortli -Eastern Area See note 2 to 6 I^ote. — Reception doubtful, due to atmospherics and jamming by American stations. Off' Japan ... 3 4 Some jamming by Japanese stations. Cliina Seas 3 3 Some jamming. East Indies No observations (> Off Mexico „ 1 to 3 Gulf of Panama to 4 2 to 4 Unreadable through atmospherics. Off Soutli America 3 to 4. 3 to 4 Considerable jauuning by American and Argentine stations. Central South Pacific 4 to 5 4 to 5 Off Cape Horn No observations 5 AUSTRALASIA— Off Northern Australia ... No observations 6 Off Western Australia ... 4 4 to 6 Australian Bight .. 3 to 4 5 to 6 North of Tasmania 4 5 Off Sydney, 4 5 Off Brisbane ... [[] 4 5 New Zealand, North Island 5 5 New Zealand, South Island 2 4 UNIVERSITY OF CALIFORNIA AT LOS ANGELES THE UNIVERSITY LIBRARY This book is DUE on the last date stamped below U«l M«6 Form ^,-0 lOni -3, '30(7752) TTof CAUFOKNU WARY 8670 rr7A4 Gt. Brit. ■7i Pftless v.1-2 telegraphy ftoirnnission - Report. HE 8670 G7A4 v.1-2 3 1158 01113 8061 UC SOUTHERN REGIONAL LIBRARY FACILITY AA 001 290 053 6