We found this circuit in the June 1987 issue of Radio Electronics magazine. With it, it is possible to receive signals from the bands determined by the crystals in a common medium wave receiver.
The integrated circuit can be replaced by more modern operational amplifiers like the 741. The...
We found this circuit in the August 1970 issue of Radio Elecronics magazine. It uses the CA3018...
The configuration shown in the figure is quite simple and can be used to activate a signaling LED...