This circuit was found in American documentation from the 90's. The transformer determines the output voltage. The transistor must be equipped with a heat sink.
Found in Motorola documentation from the 1980s, this circuit employs an integrated device from...
Found in the American 73 magazine for radio amateurs, this circuit can test common quartz...
This simple 1-transistor MW radio for listening on the phone was found in a Japanese magazine in...