We found this tube receiver in a 1950s Japanese publication. The circuit uses 5 tubes and has an RF amplifier stage for greater sensitivity. The power supply is not shown on the circuit.
This flood or humidity alarm was found in an English publication in 1991. It can still be fitted...
This simple transistor tester uses a common 3 mA analog instrument that has its scale changed as...
This RF amplifier step has a dynamic range of 140 dB and can amplify signals from 0.5 to 40 MHz....