This circuit was found in a 73 magazine for radio amateurs from the 90s. The circuit uses high voltage transistors and the relay is high voltage as well.
This circuit generates 50, 100 and 200 Hz signals from a 3.2768 MHz crystal and has outputs...
This circuit allows frequencies between 1.8 and 30 MHz to pass. Data for the coils is provided next to...
The automatic heating system sensor is a diode placed in a waterproof tube as shown in the figure....