This circuit covers 400 kHz to 40 MHz in three bands according to the selected coil. The double MOSFET allows equivalent, since the original is not easy to obtain.
Obtained from an English publication, this circuit actually needs a current limiting resistor,...
This 2003 circuit serves to digitally show the intensity of a sound captured by a microphone....
Suggested by a Popular Electronics from the 90s, this circuit uses a buzzer to indicate the...