The circuit shown here is a ZN414 or MK484 AM radio receiver with TDA7052 Amplifier. ZN414 IC has been discontinued few years ago and now MK484 and TA7642 am receiver ICs has taken its place. The internal circuitry of these ICs are similar to ZN414, and also the external package TO-92.
These ICs contain complete am radio circuit in them and requires only few external components and a single transistor amplifier for driving headphones. But we have made further improvements to the circuit and connected a TDA7052 amplifier IC for diriving an 8 ohms speaker. The transistor Q1 is working as a preamplifier which increase the faint audio signals of stations and send it to transistor Q2 which is working as a small audio amplifier, the audio signal is then reveived by TDA7052 IC which further amplifies it to drive an speaker. The 10K potentionmeter before Q1 is used adjust the strong and weak audio signals of the stations, and 4.7K potentionmeter near the TDA7052 is used to adjust the volume.
The max operating voltage of MK484 am receiver IC is 1.8 volt DC. Due to which two 1N4148 diodes are used to step down 9 volts comming from the battery to 1.2 volt to operate the AM radio IC. 250 Ohms variable resistor is used to set the MK484 on best possible reception. Tune any station and adjust the 250 Ohms variable resistor and stop where you get good reception. Coil L1 is equal to 55 turns of 0.315mm (30 swg) enamelled copper wire wound on 10mm x 100mm long ferrite rod, also experiment with more or less number of turns to achieve best performance. You can also try other am radio coils you have in scrap, For further improving the reception use AM loop antenna.