Armstrong oscillator

The Meissner patent from 1913 describes a device for generating electrical vibrations, a radio transmitter used for on–off keying.

Both circuits are sometimes called a tickler oscillator because the distinguishing feature is that the feedback signal needed to produce oscillations is magnetically coupled into the tank inductor by a "tickler coil" (L2, right).

In that application, the input radio frequency signal from the antenna is magnetically coupled into the LC circuit by an additional winding, and the feedback is reduced with adjustable gain control in the feedback loop, so the circuit is just short of oscillation.

The circuit diagram shown is a modern implementation, using a field-effect transistor as the amplifying element.

In the Meissner variant, the LC resonant circuit is exchanged with the feedback coil, i.e., in the output path (vacuum tube plate, field-effect transistor drain, or bipolar transistor collector) of the amplifier (e.g., Grebennikov, Fig.