Wednesday, January 28, 2009

Karl Braun rectifies

Yesterday I covered an improvement in crystal rectification. While it may seem crude, it was an advancement. And like any "break-through" it begat others, and was based in those that preceded it. I specifically noted Karl Braun. He is best known for invented the first cathode-ray oscilloscope in 1897. It's a big flashy invention with a fluorescent screen. But he also defined the basic principles of rectification, which while not as ostentatious was more important.

Rectification simply put is converting AC to DC. In radio this is a crystal detector, or a diode. Braun had been studying the conductivity of metal salts in solution, what we call electrolytes. he found that they conducted electricity even when not dissolved. He then made an examination of metallic sulfides. He discovered that in many metal sulfides the electrical resistance varies with the magnitude and polarity of the applied voltage. Viola! rectification. More specifically this was the "point-contact rectifier effect."

He went on to write a paper in 1874 on current flow through metallic sulfides. This was before radio, so it's implications were not immediately obvious to him. It was Sir Jagadis Chandra Bose, who made that leap and applied to patent the idea in 1901. In the U.S. we teach that Marconi invented radio. In Germany I understand, they're a little better at mentioning that Dr. Braun shared that 1909 Nobel Prize for physics with Guglielmo Marconi for developing the "Wireless."

Unlike Losev, Braun was an academic. He'd even published scholarly articles while in high school. He attended the University of Marburg and earned his Phd at the University of Berlin in 1872. He taught physics at the University of Strasbourg. His career is well documented. But I find two different stories of his death. One tale tells of him defending his patents on his discoveries. In 1915 he traveled to New York City to go to court. the intimation is that he is defending a closed circuit design that improved upon Marconi's open circuit design. The other tale has him headed to New York to defend the German Telefunken wireless station at Sayville, N.Y. Defending it from none other than Marconi. I lean toward this second version as I can confirm that in 1915 said trial was at least extant.

Both stories end with him being detained because of his German citizenship. Unable to return home, he bought a house in Brooklyn, and died in April of 1918 without having ever returned to his homeland.