4 transistor AM MW radio

TRF AM MW radio ( 2-V-2 ) with 4 transistors. With trim pot set best sensitivity DC biasing for VT3 transistor, U b-e about 0,,62V Transistor VT3 is a AM demodulator - audio amplifier. If problems with motoboating oscillation sound, need flip coupling coil 180 degree. Circuit use negative feedback loop for stabilising all transistors DC biasing. External antenna: random wire loop ( about 2, )