Invented by Nikola Tesla in the 19th century, and much beloved of science fiction film makers of the 30's and 40's, as well as hv experimenters of today, the Tesla coil is an inexpensive way to generate very high voltages (megavolts) at radio frequencies. A tesla coil consists of an air core inductor that acts as a quarter wave transmission line shorted at one end and open at the other. The shorted (low impedance) end is driven by link coupling from a high power RF source at the resonant frequency of the transmission line. The impedance transformation of the quarter wave line turns the high current, low voltage at the shorted end to very high voltage, low current at the open end. The most popular RF source is a resonant LC circuit excited by an impulses created by a spark gap.
There is an immense amount of information on Tesla coils available on the web, some of it good, some of it positive dreck. Start with Bill Beatty's page at www.eskimo.com/~billb/.
Copyright 1997, Jim Lux / Back to home page / Mail to Jim