Found in a Motorola documentation from the 70s, this circuit makes use of transistors of the time. Modern equivalents can be used. The diode also supports an equivalent.
This small converter using Only one transistor was published in the Radio Electronics magazine from...
This circuit was found in a Popular Electronics of the 1990s. Its purpose is to expand the scale of...
This receiver was found in old English documentation and any general purpose NPN transistor can be...