Found in a 90s Popular Electronics, this circuit allows to select the operating ranges between short waves and VHF. MOSFET is uncommon today.
This circuit is from a publication from the 70s, but it can be assembled with any diac and a Triac...
This circuit was obtained in a 1983 publication. It is a 1-transistor voltmeter, capable of...
This circuit from Radio Electronics magazine, March 1994 edition uses two LM388 bridged, providing a 4...