The Modern Armstrong Regenerative Receiver

Lee de Forest’s invention of the Audion in 1906 led to marvelous developments in radio
receiver technology. But it was not until Major Edwin H. Armstrong conducted a
thorough investigation of the principles of operation of the new three-electrode tube that
the technological jump took place. Mr. Armstrong applied in 1913 for a patent on the
regenerative receiver, one of the most famous radio inventions, maintaining a long
litigation in the courts with the inventor of the Audion. However, he managed to
develop a large number of radio circuits utilizing the principle of regenerative
amplification or equivalently, positive feedback in amplification circuits.

The pioneering work of Major Armstrong on the regenerative receiver has come to our
days in the form of the so called Armstrong circuit, the most popular receiver used by
experimenters and Hams throughout the world. Its most basic representation is depicted
in Fig below.