The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This good gain antenna up to 30 MHz was found in an American 1990s documentation. The circuit can be...
This circuit was found in an English magazine from 1973. The magazine no longer exists, but the...
This is a battery powered 3W power amplifier using germanium transistors. The circuit is from an...