Tesla Notes 12: The Oscillation Transformer, or the Coil (1891)
Why the induction coil fails at high frequency, and how a condenser, a spark and two tuned circuits without iron became the Tesla coil of patent 454,622.
Tesla tunes two coils without iron, derives their two frequencies and the voltage gain √(L₂/L₁), and files patent 454,622 for the coil.
Nikola Tesla
November 5, 2026
28 min