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.
Other voltage comparators can be used in this circuit that we found in a Popular Electronics from...
Published in a February 1978 Radio Electronics magazine article, this digital circuit uses some of...
This circuit was obtained in an English magazine from 1980, but it can be easily assembled today....