The purpose of this circuit is to measure the resistance of an antenna at the resonant frequency. The circuit is from an old American documentation for hams.
In the figure we have a battery charging circuit for currents up to about 5 A. In series with the...
This circuit consists of an electrostatic sensor that can check if a cable is energized by simply...
This relay triggered by voice or by another sound was found in an Elektor from the 90's. The...