We found this circuit for receiving shortwave on a mediumwave radio in a 1986 Hobbyst Electronics PE. The circuit has the received band given by T1 which can be an FM IF.
This conventional series reducer circuit reduces the voltage of a 12 V battery to the selected value...
In the figure we have a converter that generates a negative voltage from a positive voltage...
This circuit covers the bands from 1.8 to 150 MHz, with plug-in coils whose characteristics are...