Using the LM3909 this circuit was found in the January 1992 issue of Radio Electronics magazine. Resistor R1 should be chosen according to the table given next to the diagram.
This circuit, found in a 2008 documentation, is intended for operation by radio amateurs in the 7...
This circuit was found in a Texas Instruments linear application manual. The circuit uses an...
This code practice circuit was found in a 1990s issue of Radio Amaterur Today magazine. It...