TA7642 AM Radio tutorial. Best Circuit

You can add an SW circuit by obtaining a dual
gang PVC that has 350 pF to 130 pF. Also an
IFT with Transistor to make the resonance of
required SW Frequencies (a Local Oscillator and
Mixer Transistor), then feed signal to the input
of TA7642 instead of the AM tuner.
This can be done by using BAND Selector Switch.