The circuit is a high performance AM receiver based on the Philips TDA1572 IC. The TDA1572 is an integrated AM receiver circuit that has all the essential circuits such as RF amplifier, mixer, IF amplifier, AGC circuit, the pilot signal strength indicator, audio pre amplifier, etc. controlled oscillator incorporated into it. The internal oscillator frequency can be up to 50 Hz and the IC can accept RF signals up to 500 mV. HF inputs are static protected and separate buffer, voltage controlled oscillator makes it possible to use single coils in the circuit.
Inductor L1 connected between pins 14 and 13 of the IC sets the frequency of the oscillator. Potentiometer R12 is used to vary the voltage on the varicap tuning diode D2. C4 is associated with the internal balance of full-wave detector circuit. Pin 11 is the circuit output if the internal field indicator of strength. The power available on this pin is a function of field strength available and has a good linearity for logarithmic input signals.
The intermediate frequency of this circuit is built around 455 KHz. The band pass filter circuit ago about CF1 and CF2 6kHz select the band around the intermediate frequency. In simple words, IF double-balanced mixer output available on pin is filtered and applied to the input of gain controlled amplifier filter capacitors C16 and C17 are used to reduce the solution time of AGC. The transistor Q2 and associated components form the driver circuit M1 field strength meter. Resistors R9 R5and preset can be used to configure the meter. Capacitor C3 is a bypass capacitor for the audio preamplifier circuit of frequency within the IC. Capacitors C16 and C12 prevent noise (if any) of the power line.
TDA7052 is an audio stage 1W amplifier to drive the speaker. TDA7052 is an integrated bridge amplifier that can deliver an output power of 1W at 8 ohm speaker. Capacitor C18 couples the audio output of the TDA1572 to TDA7052. Potentiometer R10 can be used to control the volume.
