We found this circuit in an American publication from 1977. The circuit drives two LEDs according to the control of the inputs. The technology is TTL requiring 5 V to power supply.
Found in a QST from the 90's this circuit is suitable for the medium and short-wave range. |...
We found this circuit in documentation from the 1950s. The circuit basically applies to germanium...
We can also use the 4011 on this CMOS circuit that makes use of a crystal headset. The power...