This simple receiver of two transistors for the 80-meter range was found in an American documentation from the 1980s. The transistors admit equivalents and the antenna must be long.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
Suggested by National Semiconductor, this circuit can be applied to almost any operational...
This circuit was found in Radio Electronics from the 90s. The circuit can generate signals up to...