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 sought out Edison for employment in 1886. Starting as an instrument tester, Reg rapidly progressed to head of the department. Edison at the time was very heavily involved in generation of electricity. The early machines were finicky and troublesome at best, and Reg became one of Edison's best field troubleshooters, where he impressed wealthy Edison clients like J.P. Morgan. He also met, rubbed shoulders with, and became friends with the likes of Lord Kelvin, George Westinghouse and the Wright brothers. He went on to become Edison's head chemist, where he developed the first flame resistant insulation for electrical wires.

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 Atlantic (there has been some debate in recent years that his equipment wasn't good enough to succeed), but Fessenden was definitely the first to communicate both ways across the Atlantic. But ultimately Reg was obsessed with the idea of transmitting the human voice over wireless. The skeptics, including Edison, thought he was crazy. This was in the very beginning of the 1900's, a good twenty years before vacuum tubes would come on to the scene. All that Fessenden, Marconi and their contemporaries had to work with were coils, primitive capacitors, and whatever they could make with their own hands in their laboratories. Thus was born the spark transmitter: an AC source, keyed to supply bursts of energy to an LC tank circuit, which was coupled to an antenna. When energized, the LC circuit oscillated for a short time, producing an RF pulse.

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.)

But voice 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 Edison's General Electric plant to build a high frequency alternator, a task at which they ultimately failed. No matter, Fessenden himself made an interrupter capable of 10 kHz, and freely gave the information back to GE. GE's so-called Alexanderson alternator would more properly be named a Fessenden alternator!

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.