This circuit shows how to simulate a high-performance diode with two diodes. The circuit is from a 1960s RCA documentation. Modern general-purpose transistors can be used.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
This source was obtained from a book on transistors from the 60's. The circuit uses germanium...
This powerful inverter provides a high-quality sine wave signal. I found it in a Radio Electronics issue...