These 6 to 12 V source with current up to 100 mA was found in Radio Electronics magazine from June 19666. The source has a current indicator and uses transistors of the time.
Similar metronome settings can be found at several points in this section. This was taken from a...
This transmitter for the 40 meter or 7 MHz band was found in a magazine 73 for radio amateurs of...
This circuit is from a 1998 Electronics Now and can be easily assembled since it uses a common...