Found in an old publication, this is a transmitter with a spark coil. The high frequency oscillations of the high voltage spark generate the signal thrown at the antenna.
In the figure below we have a typical circuit for applying a current sensor that can be used in...
A quartz crystal-controlled oscillator, capable of operating up to approximately 1 MHz, can be...
This low power, class A circuit uses two old germanium transistors. The circuit was found in an...