This circuit was obtained from an Electronics Design of 1964. The circuit makes use of tunnel diodes that are uncommon today. The circuit works with very weak signals.
This Popular Electronics circuit can be found in various versions on this site and in this...
Found in a 1964 CQ magazine this circuit consists of an automatic telegraphic key, providing the...
This fourth-order circuit was found on an 80's Radio Electronics. The power supply must be...