Marconi and the invention of Radio

The theory of energy waves - or wireless waves - in :he air was first put forward in 1864, ten years before Marconi was born by the British physicist James Clerk Maxwell, Professor of Experimental Physics at Cambridge University. Maxwell produce by brilliant mathematical reasoning, the theory that 'electro-magnetic disturbances', though invisible to our eves, must exist in space, and that these waves travel at the same speed as the light waves - that is, at the rate of 186,000 miles, the equivalent of more than seven times round the world, per second.

This was a very remarkable deduction; but at that time no means of producing and detecting such waves were known, and Maxwell was, therefore unable to carry out any scientific experiments to prove the truth of his theory, and had to leave it to others to show how correct his reasoning had been. Twenty-four years later the German physicist, Heinrich Hertz, was able to show that, when he produced an electric spark across a gap between two metal balls by applying an electric current to them, a similar spark would jump across a small gap in a metal ring a few feet away, though the ring was not connected in any way with the other apparatus.

The experiment made it clear that the second spark was caused by the first, and the fact that there was no connexion between the balls and the ring suggested that the spark from the first apparatus must have been transferred through the intervening space between the two pieces of apparatus in the form of some kind of wave spreading outwards in all directions like light. In fact, it was clear that those were the electro-magnetic waves of Maxwell's theory.

Marconi began his work by fixing up a simple contraption, similar to the one used by Hertz in his discovery, and trying this out on a table. Then, when he, too, had succeeded in making a spark cross from one apparatus to another, he designed a more elaborate set-up and tried to reproduce a bigger spark and at a greater distance. He spent weeks making and testing new pieces of equipment, and then breaking them up again when they proved to be useless. He had so many failures and disappointments that he sometimes felt quite desperate; but he persevered, and eventually succeeded in sending a spark the full length of a thirty-foot room.

Though Marconi was naturally delighted with this development, it was clearly only a beginning; he must now try to make his sparks do something useful. This meant more gadgets and more experiments. Then, one night after the rest of the family had gone to bed, he succeeded in making the wireless waves start an electric bell ringing in a room two floors below his laboratory. He was so excited that he rushed to his mother's bedroom and woke her up to tell her, and the next day he demonstrated his experiment successfully to his father, too.

He extended the arm attached to one of the metal balls of the transmitting instrument into an elevated aerial and connected the second arm to earth. On the receiving instrument he also used an elevated aerial and earth. This led to an important advance, for not only did it greatly extend the range through which the waves could be transmitted, but it also increased the volume of sound received. Marconi now found that he could transmit Morse Code signals: 'I actually transmitted and received intelligible signals,' he said.

Marconi was asked to take his equipment on to the roof of the head office of the General Post Office at St. Martin's-le-Grand (London) and to send a wireless signal from there to the roof-top of another building some 300 yards away, where he set up a receiver. Both these tests were successful, and so he was then asked to give a third demonstration - this time on Salisbury Plain - to a group of high-ranking army and naval officers and government officials. This third demonstration was naturally a very important one for Marconi. He therefore took immense pains over his preparations, testing and re-testing his apparatus to make certain that everything was in order. Then, while the important spectators stood by his receiver nearly two miles away, he tapped out a Morse signal on his transmitter-and waited anxiously for the result. The signal came through perfectly.

The following March, a German vessel collided in a fog with the East Goodwin lightship off the Kentish coast, and, for the first time, a distress signal calling for relief was despatched by wireless - and was answered. This was a remarkable proof of the importance of radio to shipping, and not long after most of the larger nations were fitting their ships with wireless equipment.

'He'll be sending messages across the Atlantic next,' people joked, never for a moment believing that this might really be possible. But it seemed no impossibility to Marconi, and shortly after a visit to the United States he seriously set to work to achieve the sending of a signal from Great Britain to America across the Atlantic Ocean.

He chose a lonely spot on the south coast of Cornwall called Poldhu, high above the cliffs near Mullion. Work on building the new station began in October 1900. The following January the elaborate new plant was installed, and then Marconi, with his usual careful attention to detail, spent several months testing it and suggesting improvements. Then on 27th November 1901, Marconi with two of his assistants, Kemp and Paget, sailed for Newfoundland, 2,000 miles away, where they intended setting up both a receiver for the reception of the signal from Poldhu and a transmitter for sending a second signal back to Cornwall. The small party successfully installed their receiver at St. John's in a disused hospital attached to a naval barracks on a 500-foot hill which, strangely enough, was called 'Signal Hill'.

As the weather was growing rapidly worse, Marconi decided to concentrate upon trying to receive a signal from Cornwall. So he sent a cable back to Poldhu giving instructions for the three Morse Code dots representing the letter 'S' to be transmitted at frequent intervals each day, starting on 11 December. He heard nothing on the first day except for the roar of the gale outside. On the second day, 12 December, the gale was so strong that it blew away the kite supporting the important aerial and a second kite had to be hoisted. But that afternoon, just as he was beginning to think that his experiment had failed, Marconi heard, very faintly, the sound for which he had been listening, the signal from Poldhu ... ... ... ...

(From Great Inventors by Norman Wymer.)