The chief difference between his transmitter and that of Hertz was a telegraph key which he put in the battery circuit so that he could break up the sparks into dots and dashes. He also set a reflector back of the apparatus to concentrate the electric waves into a beam to make them go in a given direction when they would be more powerful and cover a longer distance. But Hertz did the reflector stunt first.
Marconi’s receiver was made up of an apparatus just like Popoff’s except that he connected an old-time Morse printing register in the battery circuit so that when the electric waves acted on the coherer the signals would be printed on a tape in dots and dashes.
In his first attempts, then, to send wireless messages, young Marconi had done four things and these were (1) to see the possibilities of using electric waves set up by a Hertz apparatus for sending messages; (2) to put a telegraph key in the sending circuit; (3) to use a Popoff receiver for receiving the electric waves, and (4) to put a Morse register in the receiving circuit. These were the first big steps in building up a wireless telegraph set, but none of them formed an invention.
I do not know just when Marconi added the aerial and ground to his transmitter—Popoff had used an aerial and ground with his receiver—but the aerial and ground formed his great claim to being the inventor of the wireless telegraph, for it was the aerial and ground which enabled him to cover long distances.
In 1896 Marconi went to England and there applied for a patent in which he showed an aerial and ground connected to his sending and receiving apparatus (see the diagram) but even at this time he did not understand the importance of a high, well insulated aerial and a good ground.
On arriving in London this boy, with the big idea in the back of his head and a lot of business ability in front of it, went to Sir William Pierce who was then at the head of the British Post Office and offered to give him a demonstration of his new wireless telegraph. As Sir William had long been interested in the possibility of wireless telegraphy he was agreeable. The outcome of it was that one station was rigged up in the General Post Office and another on the Thames embankment about 300 feet away.
These experiments were successful enough to interest the War Office and he was asked to show what he could do over longer distances. Salisbury Plain was chosen for the trials and by placing reflectors back of the sending and receiving apparatus he was able to telegraph over a distance of about 2 miles.
Marconi now commenced to experiment with aerials and grounds in order to increase the effective range of his apparatus and with them he was able to cover the distance of 3 miles between Lowernock and Flat Holm. Sometimes in these trials the dots and dashes would be printed good and clear and at others they were all jumbled up.
The inventor was trying all sorts of schemes to get satisfactory results, but nothing helped until he heightened the aerial wire on his sending apparatus. Presto! the signals came in clear and without a miss. Here then was the whole secret of wireless telegraphy—the higher the aerial the farther messages could be sent with the same amount of power.