REG FESSENDEN CLEARS HIS THROAT
The first radio broadcast in history, and the first voice that ever modulated an RF wave, was Canadian. That voice belonged to one of the true giants of invention of the twentieth century, and one of the great injustices of our school system is that he is not known better. Nevertheless, Reginald Fessenden had a remarkable life.
While at school, Fessenden decided that he wanted to be an inventor, and
Lured away by Westinghouse to be his plant supervisor, Reg was able to finally make light bulbs a paying proposition, by replacing what had been platinum leads with ferrosilicon alloy, which was much more economical and had a coefficient of expansion that matched the surrounding glass envelope. He improved existing telegraph systems enormously, and along the way he invented microfilm, sonar, and a very lightweight internal combustion engine. The engine was never developed into a commercial unit, but Ferdinand Porsche apparently borrowed heavily from Fessenden's design when he built the original Volkswagen motor.
Alarmed by the sinking of the Titanic, Fessenden invented sonar as a means to detect icebergs in poor visibility. He was able to further develop it into an effective detector of U-boats during WWI. He also patented geotechnical acoustic mapping, an innovation that later made him quite rich.
But on to radio:
Marconi may or may not have sent the first wireless signal across the
It was Fessenden who first realized that things worked much better if the LC circuit oscillated at the resonant frequency of the attached antenna, and he patented this innovation. And in an era without diodes, he developed a vastly improved RF detector, called an electrolytic detector. (That scoundrel Lee deForest visited Fessenden, saw the detector, copied it, and called it his own, renaming it the "spade detector." Fessenden successfully sued his butt off.)
transmission proved elusive. Fessenden realized that he'd need a much higher frequency
of AC to transmit his voice (Nyquist's Law, not yet
discovered, was already in effect). He
tried to get his old friends at
Fessenden's interrupter took the place of the telegraph key, and provided 10 kHz pulses to the tank circuit. He then placed a carbon microphone between the tank circuit's RF output and the transmitting antenna, in the process inventing amplitude modulation, or more accurately, pulse amplitude modulation. Surprisingly, Fessenden's new signals were backwards-compatible with Marconi's Morse receivers. Can you imagine the effect that hearing voices and music (Fessenden's violin!) in their earphones had on radio operators listening to Fessenden's first broadcast, Christmas Eve, 1906?
I'll have a little more to say about Professor Fessenden in a future column.