A Revolution in Mans Ability to Communicate
It had taken over a year to prepare the massive aerials and the cumbersome, infuriatingly fragile equipment that went with them, and there was setback after setback. The two-hundred-foot masts were smashed to matchwood in a gale, shorter ones proved inadequate, kites seemed the answer. Then they, too, blew away. Eventually, however, the massive arrays were ready in Cornwall and, 2,100 miles away, in Newfoundland. In the middle of an icy night, Marconi in Newfoundland huddled over his receiver, was able to hear the three dots, faint but unmistakable, of the Morse code letter “s”. The first “wireless” message had been sent across the Atlantic: from now on, the distance would be annihilated; man would be able to speak with man, a nation with nation, from the uttermost ends of the earth.
The achievement was immense: the idea was old. Clerk Maxwell had predicted the whole thing in his 1873 Theory of Electricity and Magnetism, which proved that “electro-magnetic waves” were set up by any oscillatory electric current, that is to say, a current that repeatedly changed its direction. These waves, he said, were similar to waves of light and travelled at an incredible speed of 300,000,000 metres, or 186,000 miles, per second. He predicted that they would some day be detected or “received” at a great distance. Fourteen years later the German, Heinrich Hertz, demonstrated to a delighted audience that the waves could be generated by a spark, leaping across a narrow gap, and that the waves would produce a smaller, sympathetic spark across a gap some distance away.
In England, Oliver Lodge, working at much the same time as Hertz, developed the “coherer”, which had been discovered by Edouard Branly in Paris. Branly had shown that a container full of metal filings, if placed in the path of these waves, would cohere into virtually a solid bar of metal, a conductor capable of carrying electricity. Lodge found that an electric current from a battery could in effect be switched on by the waves, if it were passed through such a coherer, and that this current could be used to ring a small bell.
Lodge solved one of the coherer’s chief disadvantages by placing the electric bell so its clapper struck the glass side of the coherer; with the earlier experiments, once the device “cohered” and permitted current to flow, it was impossible to stop that current without disconnecting the battery, the stopping of the electro-magnetic waves didn’t “un-cohere” the filings. With the bell’s clapper striking their container, the filings were continually being shaken apart, then reassembled by incoming waves. When the waves stopped they remained loosened and no current flowed. It was now possible, by switching the wave-source, the “transmitter”, on and off, to produce a similar on-and-off effect at the receiver and by means of it to send the letters of the Morse code.
But the coherer had many disadvantages and it was left to others, among them Marconi, to develop a more sensitive and reliable receiver from a magnetic needle which flickered in time with the incoming waves. It could be read quite simply by eye: a brief deflection was a “dot”, a longer one was a “dash”, and with a little practice it was easy to make out the separate letters of the code from the singleton dot of the letter “e” to the ponderous two-dashes one-dot one-dash of “q”. By attaching a pen to the needle a record of the message could be kept on a moving strip of paper. Then Marconi found he could simplify the reading of the message if he used the needle, like a switch, to open and close a circuit which would ring bells, sound buzzers, light lights.
Guglielmo Marconi, the man who made possible wireless telegraphy, and hence broadcasting and television, was born on 25 April, 1874, a year after Clerk Maxwell’s prediction. He soon developed an interest in electricity and began to experiment in the family attic in Bologna, playing with wires and batteries among the silkworms. His Irish mother seemed somehow to realize her son might produce a valuable invention from his piles of home-made equipment. His father, Giuseppe, deplored the time spent on “childish experiments”, destroyed every bit of electrical equipment he found in the house.
After the details of Lodge’s coherer had been published, the young Marconi set himself to improving it. Night after night he sat in the attic of the Villa Grifone and experimented with different shapes of container, different proportions of zinc and silver filings, different quantities. From the coherer, he progressed to a magnetic detector and with the help of his older brother Alfonso he sent and received messages from one end of the attic to the other, from the attic to the far end of the garden, across two fields.
All of this was encouraging, but suddenly he realized that if the phenomenon of wireless telegraphy were to have much practical use the waves from the transmitter would have to go round or through buildings and hills. In fact, and here Marconi was looking, as he always did, into the future, the waves would have to follow the curvature of the earth, or they would get as far as the horizon and disappear into space. The two brothers had been using a visual system of return signalling, with Alfonso waving a handkerchief to tell his brother up in the attic whether he had read the message; for this next experiment, visual signalling would be useless. Guglielmo gave his older brother a hunting rifle and told him to go with the receiving apparatus to the far side of the hill behind the house.
Alfonso’s walk over the rim of the hill, carrying heavy equipment, took twenty minutes. Guglielmo watched from his attic window until his brother disappeared.
“After some minutes”, he wrote later, “I started to send, manipulating the Morse key. And then, in the distance, a shot echoed down the valley.”
And so, in September, 1895, the first practical radio transmission was made. The boys’ father was admitted into the secret and he, after seeking advice from the parish priest and the doctor, directed his son to take the invention to Italy’s Minister of Posts and Telegraph. The Minister, incredibly, had no interest in the young man’s discovery, and Guglielmo, hurt and disappointed, decided to take his invention to England. His mother agreed that this was the wisest move and accompanied him across the Channel. Here, English Customs officials, horrified by the wires, batteries, dials and condensers they found in the Marconis’ baggage, decided the pair must be dangerous regicides, on their way to blow up Queen Victoria: after all, the French President had been assassinated only two years before. Eventually mother and son, almost in tears, convinced the officials that they were only harmless visitors with a new invention, but by this time the invention had been wrecked, the packing cases were full of torn wires, broken batteries, twisted dials.
Annie Marconi’s brother Henry met them at Victoria Station, consoled them and arranged their accommodation, after which he dashed round London assembling the materials with which his young nephew might rebuild the smashed apparatus. Cheered by this kindness, Marconi set to work, harder than before, and by July of 1897 was able to lodge at the Patent Office in London a complete specification for “Improvements in Transmitting Electrical Impulses and Signals and An Apparatus Therefore”. He received “Patent Number 12,039, to Guglielmo Marconi of 71 Hereford Road, Bayswater, in the County of Middlesex”.
The Chief Engineer of the Post Office, an elderly, kindly, Welshman called William Preece, now took an interest in the young man’s invention and soon Marconi was using Preece’s laboratory to mount an exciting experiment from the roof of the Post Office in St Martin’s Le Grand to the Savings Bank Department in Queen Victoria Street. The signal passed through masonry walls on its way, yet was picked up loud and clear. Eagerly, the Post Office urged him to conduct more demonstrations and soon on Salisbury Plain he sent signals a distance of ten miles. Then, to the amazement of his audience, he sent a message across the Bristol Channel.
The Royal Navy became interested and at last the Italian Government, hearing rumours of the wonderful things the young man from Bologna was doing abroad, asked him to return. Guglielmo was delighted to do so and performed a number of experiments at the naval base of Spezia, establishing contact with ships across ten miles of water. The Italian Government now urged him to make his home in Italy, but with his own “Wireless Telegraphy and Signal Company” just formed in England, this was out of the question. He agreed, however, to change its name to the unmistakably Italian, “Marconi’s Wireless Telegraphy Company”.
For years, from the days of the attic in Bologna, he had dreamt of sending a message across the Atlantic Ocean and in 1901 he was able to do so, sending the letter “s” from Cornwall to Newfoundland. (Why “s”? Simply, Marconi explained, that one dot might be accidental, an interference from the earth’s magnetic field, or from distant lightning; so, conceivably, might two. But the three dots of the letter “s”, repeated at regular intervals, these would be unmistakable.)
From now on development was rapid. In Britain, Fleming invented the thermionic valve, utilizing the discovery that a heated wire or “filament” would give off negative electrons which could travel through a vacuum and be picked up by a positively charged plate. The electrons could only travel in this one direction, from filament to plate, and thus Fleming had hit upon the first one-way circuit. By connecting a receiving aerial to Fleming’s valve in such a way that the minute oscillating current which came down it, changing direction thousands of times a second, became a direct current, fluctuating, but always in the same direction, the current could be used to perform various tasks. Two years later, in 1906, the American Lee de Forest added a third part to the valve, a grid of wire mesh which he interposed between filament and plate, making the first “triode”. This remarkable device not only converted feeble alternating currents into direct, but amplified them many hundreds of times, thus greatly increasing the range of wireless communication. A little later it was discovered that the same triode valve could be used to transmit waves, in place of the inefficient spark gap.
The next two developments, in which Marconi played a large part were the “tuning” of transmitter and receiver to the same frequency of oscillation and the “modulation” of the wave so that it would carry, not just on-and-off signals, but speech and music. The first enabled transmitters to be set up independently, working on different frequencies and not interfering with each other: receivers could be tuned to each or any of them. It also greatly increased the power of the signal. The second development made possible not only broadcasting but, some years later, television. De Forest’s valve was used for this modulation, by which the slower pulses of a musical instrument or a voice (middle “A” for example has a vibration of 440 times a second) could be impressed on the rapid vibrations of the wireless wave (of the order of hundreds of thousands, even millions, per second). At the receiver, the wireless wave, now christened a “carrier wave”, would be jettisoned and only the superimposed information used. A loudspeaker could be made to vibrate in sympathy with it, reproducing the sound of the original.
A major discovery for which Marconi is almost entirely responsible is long-distance short-wave transmission. He proved that the shorter radio waves did not, in fact, cling to the surface of the earth, but that most of their power shot off into space. This apparently discouraging property was of immense value: it allowed the waves to be reflected off layers in the atmosphere, returning to earth hundreds of miles from their point of origin, unweakened by absorption into the earth. By working out an angle of projection mathematically, it was possible to arrange that a short-wave beam returned to earth at a predestined point and bounced off again to return second, third, fourth and further times till it had girdled the earth. And by beaming the signal, rather than letting it scatter in all directions, as with longer waves, there was a huge saving in the power required.
The principle of short-wave transmission, on which all international radio communication depends, was developed further, With shorter and shorter waves and higher frequencies. (From Clerk Maxwell’s wave-speed figure of 300,000,000 metres a second we can see that a frequency of 100,000 cycles of waves per second must give each one a “wave-length” of 300 metres; a frequency of 10,000,000 cycles per second would give a wavelength of 30 metres.) The very short waves, it was discovered, could be directed like a beam of light and picked up again when they bounced off an object: the discovery on which radar depends.
Guglielmo Marconi, who did more than any man to develop radio, died in 1937. By that time he had seen his brain-child grow from a wriggling needle in an attic to a world-wide system of communication and a world-wide means of entertainment. There were broadcasting stations in every country in the world; only a few months before he died, the world’s first television service, developed by J. L. Baird from Marconi’s short-wave studies, went on the air in Britain.
Much of the enormous post-war development of radio communication might have been forecast by Marconi. Probably the change he would notice most is the use of “transistors”, little crystals which perform most of the functions of the thermionic valve but are minute in size and use tiny quantities of electricity. The modern “transistor portable” is an accomplished, only too noticeable, fact and its small components, developed only since 1948, have made complex mathematical computers, using tens of thousands of circuits, a physical possibility.
- Robert (Bob) White, Guglielmo Marconi – Aerial Assistance with a Kite. Bridging the Atlantic By Wireless Signal – 12 December 1901. Kiting, The Journal of the American Kitefliers Association. Vol. 23, Issue 5 – Winter 2002. November 2001
- Faking the Waves, 1901
- Marconi and “wireless telegraphy” using kites