This circuit is from a March 1978 Radio Electronics magazine article that showed how to build it. The circuit is TTL based and is powered. The components used can still be found.
Found in Popular Electronics from the 1980s, this circuit can use more modern transistors such as...
This circuit is from a Radio Electronics from February 1970. The integrated circuit is an...
This is stage is transformer coupled and was found in na old publication of the year 1958. The...