BEAM WIRELESS

Dominion, Volume 20, Issue 59, 3 December 1926, Page 7

BEAM WIRELESS

FIRST STEP IN IMPERIAL SCHEME BRITISH-CANADIAN SERVICE OPENED WORLD LEADERSHIP IN RADIO MAINTAINED The Marconi Company in England recently received from the Engineer-in-Chief of the British Post Office the official certificate that the wireless stations constructed at Bodmin and Bridgwater for communication with Canada on the Marconi short wave beam principle had passed their official seven days’ test, and the General Post Office then announced that a high-speed tireless telegraph service between Great Britain and Canada through these stations would be opened on October 2a. “With the first Dominion beam service thus established, Great Britain’s, world leadership in wireless communication is maintained,” says the Marconi Company in an official statement issued when the service was opened. The statement proceeds: As the home of Senatorc Marconi s first long-distance wireless experiments,. Great Britain was the pioneer country in commercial wireless telegraphy. And now, with the modem high-power valve transmitting station at Rugby for allround communication, and the Marconi beam stations for direct communication between the Mother Country and each of the Dominions, it possesses the most complete, up-to-date, and efficient wireless service of any country in the world.

Far-reaching Reversal of Policy. It was in 1923, after several years of discussion, that the Government definitely decided to proceed with the erection of wireless stations to. communicate with each of the Dominions. The Dominions had been pressing for such a service for some vears, and when the British Government’s decision was taken they immediately put arrangements in hand, for the erection of corresponding stations to form a complete Empire wireless service. While negotiations were proceeding with the Marconi Company for the erection of high-power long-wave valve transmitting stations to carry out those services Senatore Marconi became convinced as the result of his experiments, that a new svstem of wireless telegraphy could be developed that' would enable these Imperial services to be carried out much more efficiently and at much lower cost than was contemplated by the high-powcr long-wave wireless stations. ... His plan was to use short wireless waves—of 100 metres or less—which, contrary to the generally accepted theory at that time, he had proved to be quite reliable for communicating ovet great distance; and to increase the strength of signals and the speed and efficiency of working by employing reflectors to concentrate into a narrow beam the wireless energy at the transmitting station and to reflect a greater amount of energy on to the reeciving aerial at the receiving station. As Senatore Marconi has said, a considerable amount of courage was necessary to propose such a revolutionary change. He had no uncertainty, however, neither had the company, of which he is the chairman, and the proposal was put before the Government. So convincing were the arguments in favour of the new system that the whole technical policy of Imperial wireless communication was revised, and the Government entered into a contract with Marconi’s Wireless Telegraph Company, Ltd., to build short-wave beam wireless stations in England to communicate with Canada, South Africa, Australia, and India. The Governments and .wireless companies in each of these Dominions were equally impressed with the value of the beam system, and contiacted with the Marconi Company to build corresponding stations to communicate with those being erected in England. The building of the stations was started in April, 1925. They have been longer under construction, than was at first anticipated, but this lias been due to the fact that research work has been carried on simultaneously with constructional work, and many valuable improvements on the original designs have been made as the work progressed. Power valves have had to be specially designed to deal with the extra high frequencies of short-wave working, and the Mareoni oil-cooled valves at the transmitting station are the most efficient of their kind in the world.

Extraordinary Speed ot Signalling. The official Post _ Office tests laid clown that the stations for the Canadian service should be capable of communication at a speed of 500 letters per minute each way (exclusive of any repetitions necessary to ensure ■accuracy) during a daily average of 18 hours, and that a demonstration fulfilling this condition should be given bv actual working for seven consecutive days.- This test took place between October 7 and October 11, and the guarantees—which were regarded bv evervone as being extremely stringent—have been fulfilled. During these and the preliminary tests carried out bv the Marconi Company speeds of 125 ft letters per minute in each direction, equal to 2500 letters ner minute over the complete circuit, have been worked for rnanv hours on end. Counting every hour of the seven davs’ test, the average speed of signalling has been about 600 letters ner minute jti each direction, or 1200 letters per minute for the complete circuit. This result abundantly justifies the claims made for the beam system, and indicates that the stations will be capable •of handling ali the traffic that is like)v to be available between England and Canada for some vears to come. Wireless telegraph engineers are used to high signalling speeds, but the extraordinary achievements of the beam svstem have been the cause of several surprising and amusing incidents, due tn the speed of working during the recent tests. On more than one occasion the engineer has put a message on the Canadian circuit, and before he could reach the recording room in the same building he was handed the reply from Canada. Advantages to Commerce.

The institution of direct Marconi wireless telegraph services between London and Paris and other continental centres has shown that new telegraph traffic is created by the provision of new and rapid means of communication. It can therefore be confidently anticipated that the establishment of the beam services, which can be worked at a speed which will enable large volumes of traffic to be dealt with in the shortest possible time, will create new business that has not previously been possible, and so bestow a great benefit on the commerce of Great Britain and Canada. In this connection it is interesting to note that Canada has shared with Great

Britain the pioneer position, m c . om ’ mercial wireless communication since Senatore Marconi’s earliest l°nB-d*s-tance experiments in December, 1991, and the establishment of the first transAtlantic commercial wireless service between Clifden, Ireland, and Glace Bay, Canada, in 1907. By being the first Dominion to open a beam service it continues to take a lead in the development of this means of communication. The beam transmitting station in Canada is situated at Drunimondville, 30 miles east of Montreal, and the receiving station at Yamachiche, 25 miles north of Drummondville. These stations are linked up by land line to the central office of the Canadian Marconi Company in Montreal in the same way that the English stations are linked to the General Post Office. Beam stations are also being erected in Canada for direct communication with Australia, and corresponding beam stations are being built in Melbourne. The sites occupied by the beam stations at Bodmin and Bridgwater for communication with Canada are also utilised for the stations to be used for communication with South Africa. These South African stations are practically complete. Similar stations are being built at Tetney, near Grimsby, and at Winthorpe, near Skegness, for communication with Australia and India—the Grimsby stations being transmitting stations and the Skegness stations receiving stations. Corresponding stations are being built in the Dominions near Cape Town, Melbourne, and Bombay All these stations are in an advanced state of construction, and are expected to be opened within the next few months. This will complete the present Imperial scheme; but outside this scheme the Marconi Company is already engaged on a considerable development of commercial telegraph services on the beam principle. The company holds a license fropi the Post Office to conduct wireless telegraph services with certain continental countries and with all other foreign countries outside Europe. In addition to the wireless stations, it has been operating on these sendees for some years, it has a beam station nearly completed at Dorchester for communication with North and South America. A corresponding station is also in process of erection at Rio de Janeiro. Another important development in which beam stations are included, and are already under construction, is the Portuguese scheme for linking up Portugal and its colonies. Some time ago the Marconi Company obtained a concession from the Portuguese Government for the establishment of wireless telegraph stations in Portugal, and its colonies for the purpose of linking them together and establishing wireless communication with other parts of the world. These stations are now being built at Lisbon, in the Cape Verde Islands, the Azores, and in East and West Africa. When they are completed wireless services will be established with England, and the principal continental countries and with South America. The Marconi short wave beam stations in this scheme are being erected at Lisbon, Loatida and Mozambigue.

Beam System’s Advantages.

It is claimed that a beam wireless station has the following distinct advantages over any other form of telegraph communications for point to point communication over similar distances—the capital expenditure involved is considerably less; it is more economical to run and maintain; and it is by far the most speedy method of communication yet devised. The speed of working of the beam system is at present limited only by the mechanical limitations of the transmitting and recording instruments, and when suitable medns of recording over landlines at higher speeds than at present obtainable have been developed it will be possible to increase correspondingly the overall speed of signalling. The results of tests between England, and Canada have shown that the use of beam aerials at both transmitting and receiving stations has resulted in a strength of signal some 100 times greater than obtainable with non-direc-tional transmitting and receiving aerials at each end, and utilising the same power; and it has enabled the service to be carried on under conditions when signals obtained by utilising non-dircc-tional aerials were hardly appreciable. At the same time the use of beam aerials has resulted in a very large degree of freedom from atmospheric disturbance. Description of the Stations. The Bodmin station, which is built upon a strip of land bordering the main Bodmin-Truro road, 4j ‘ miles south-west of the Cornish county town, comprises two transmitting systems, one for communication .with Canada and' the other for communication with South Africa. The receiving stations are situated near North Potherton, 2| miles south of Bridgwater, off the main Bridgwater-Taunton road. The masts and. aerial system—the design of which is peculiar to the short wave beam system and is entirely different from the design previously used in commercial wireless stations—are similar at both stations. There are five lattice steel masts for each service erected in a straight line and aligned so that the great circle bearing on the distant station is at right angles to the line of masts. The beam is therefore projected accurately in the direction of the stations with which communication is being maintained. The masts are 277 feet high with cross arms at the top measuring 90 feet from end to end, and giving an additional 10 feet to the height of the mast. The aerial and reflector systems consist of a number of vertical wires, forming as it were a wire curtain, suspended from steel cables attached to the cross arms and running along each side of the row of masts. The aerial system is on one side of the masts, facing the distant station, and the reflector system is on the opposite side. The transmitter, which is rated at only 20 kilowatts, is of an entirely new design throughout, and is extremely compact. Stability of wave-length, which is of the greatest importance in short-wave work, is obtained by exceptional care in the design of the set. The transmitter is operated direct from the Central Radio Office at the General Post Office in London. The land line is led in to a relay attached to the first panel of the set. By this means the operator in London is in full control of the transmitter, and at the. moment he presses his key or feeds bis signalling tape into a high-speed telegraph instrument, the signals lie is sending are being recorded in the telegraph office in Montreal, which is connected in a similar manner to the Canadian wireless receiving station.

Tn flic stine way the messages put on to the transmitter in the telegraph office in Montreal are instantly recorded •it the General Post Office in London, after having traversed the Atlantic and passed through the beam receiving station at Bridgwater. Now that the Canadian station has been completed satisfactorily, the preliminary tests will nt once be proceeded with in the case of communication between England and South Africa. On the completion of these tests, those with Australia and India will , follow, the construction of beam stations for all these services being nearly completed.