Overvoltage Indicator (CB22007E)

Using a CA3130 operational amplifier, this circuit drives an LED when the voltage exceeds the value set in VR1.

Atmospheric noise monitor (CB21066E)
This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from...
FM transmitter (CB16327E)
This project was found in a 1982 publication. It is a small transmitter that can send signals from...
Medium wave range booster (CB21677E)
This circuit is from a 1960 book by Hugo Gernsback. The transistors are germanium from the time....