This circuit can generate signals in the VHF range and can be used as the basis for small transmitters. The frequency depends on the coil, which can have 2 to 8 turns for the range of 50 to 200 MHz.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...