Antenna tuner (CB7459E)

Found in a QST from the 90's this circuit is suitable for the medium and short-wave range.

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Power Failure Alarm (CB5949E)
We find this circuit in an American 1980s documentation. It triggers an alarm in the event of a...
741 tester (CB20888E)
This circuit allows the testing of integrated circuits of type 741 (operational amplifier) such as...
Transistorized multimeter (CB7364E)
This circuit was found in a 1967 Electronics World. We can design it with a BF245 for the FET and a...