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 circuit is simple, as it uses only one transistor and a relay that can be MC2RC1 or MC2RC2,...
We found this circuit in a 1990 documentation. It works with the power of the digital circuit...
The filter shown in the figure can operate with frequencies up to several tens of megahertz thanks...