We found this circuit in a documentation from the 90's. The coil has its characteristics given next to the diagram. Power is provided by a 9 V battery and a range of a few tens of meters.
Based on 4066 CMOS, we found this circuit in a Popular Electronics from 1992. The signal is...
This receiver of two transistors for the 3.5 MHz band was found in a circuit manual from the 80's....
This circuit uses an unusual Motorola integrated. The circuit is from Motorola's 1990 Linear...