This circuit with 4 transistors can receive signals in 6 shortwave bands. The circuit is from a Radio Electronics from May 1958. The output is for high impedance headphones.
In this 1970s receiver, the coil has a primary with 100 turns and a secondary with 20 turns, both...
This circuit was found in a 1980s documentation. Modern operational amplifiers can be used. The...
With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a...