We found this circuit in documentation from National Semiconductor. For the medium wave range the coil consists of 50 + 50 turns of wire 28 in a ferrite rod.
The optocoupler in the figure uses common transistors and a phototransistor to drive a sensitive relay...
This configuration was obtained in a 1977 FET Databook. The circuit can be practically any JFET...
It is a small circuit, which coupled to any medium or short-wave radio, allows to evaluate the...