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From Feed Line No. 8

In this age of advanced telecommunications, a thought is seldom given to those early wireless pioneers who laid the groundwork for our present wireless system. While most people associate the word wireless with radio, in reality this term can be applied to any system by which electrical energy is transmitted without wires from one location and received at another. The first investigations focused primarily on four different methods of accomplishing this: electrical conduction, electrostatic induction, electromagnetic induction, and electromagnetic radiation. All four methods showed some degree of promise, but only one of them—radio—won out.

Radio is that form of wireless communications in which the transmitter output takes the form of dissipating electromagnetic radiation, the radio waves spreading outward in all directions from an elevated antenna. Because the signal strength drops off quite rapidly as the distance from the source of radiation increases, faraway radio receivers have to be very sensitive to detect signals that may measure only a fraction of a microvolt per meter in strength. These radio waves had remained practically unknown until the 19th century when a number of important steps were taken by early investigators who developed techniques for their detection and measurement. This led to the 1886-1888 experiments of Heinrich Hertz which firmly established their existence.

Nikola Tesla's contribution to this story involved reworking the primitive sources of radio frequency current and crude tuned receiving circuits developed by his predecessors. A most important step was introduction of the coupled tuned circuit into his preliminary transmitter design. Some might recognize this as the configuration of the now familiar Tesla coil, with its primary and secondary circuits both tuned to vibrate together in harmony. By 1896 further refinements had resulted in a transmitter that could have signaled across the Atlantic, had such an attempt been made. Additional work resulted in the development of wireless receivers that also included two synchronized circuits. Between 1898 and 1903 Tesla was granted 10 U.S. patents covering his inventions in these two areas.

In 1904 Marconi was able to obtain his own patent using some of Tesla's own ideas. The issue of Marconi's patent infringement was addressed in a lawsuit brought by Tesla 1915. Nothing truly significant resulted from this action, and in a 1916 turn-around the Marconi Wireless Telegraph Company of America itself sued the United States Government for alleged damages resulting from the use of wireless during WWI. In 1943, the year of Tesla's death, a landmark ruling by the U.S. Supreme Court invalidated the Marconi patent because the fundamental radio circuit had been anticipated by Tesla. It is worthwhile noting the following definition of radio that was developed as a result of this case:

"A radio communication system requires two tuned circuits each at the transmitter and receiver, all four tuned to the same frequency."

So, the next time you pick up a wireless telephone, listen to your car radio or turn on a television set, give a quick thought to Nikola Tesla — the true father of radio.