We found this circuit in a Hands-On Electronics from the 90s. The circuit must be connected to an external amplifier. Frequency control is capacitive, using an antenna for this purpose
Found in a 1968 EEE, this switch controls a high-power load from an audio signal. The current is...
This high frequency oscillator can use any tunnel diode. Formulas for component calculations are...
This LC oscillator was found in English documentation from the 1990s. JFETs may be general-purpose...