This oscillator produces a modulated signal using a unijunction transistor. We found it in an American documentation from 1965. The circuit modulates in frequency the generated signal.
This antenna for the frequencies 146 or 440 MHz was found in a magazine 73 for Amateur Radio of...
This circuit produces 1 kHz square signals using the CMOS IC 4070. The frequency is given by the...
Found in a 90s PE Hobbyst Handbook, this circuit mimics the sound of a space gun. The components...