Here is the AM Radio receiver circuit diagram based on old single IC MK484.
|R9, R10_________ 6R8
Pot_____________ 10K log pot
Coil & ferrite bar set
|C7______________ 470p ceramic
C, C4, C5, C6_____ 470nF monoblock
C2______________ 100nF monoblock
C3, C8___________ 100uF electrolytic capacitor
VariCap__________ 60/160 AM tuning cap
D1, D2, D3, D4____ 1N4148 diode
Q1, Q3___________ BC548
IC1_____________ MK484 AM radio IC TO92
Speaker__________ 0.5 or 1W, 8 ohm speaker
The MK484 we use is a Japanese copy of the original ZN414. It contains an RF amplifier, active detector and automatic gain control (AGC to improve sensitivity) all in a 3-pin package. The input impedence is typically 4M ohm. It operates over a range of 150kHz to 3MHz. DC supply of 1.1V to 1.8V & 0.3mA current drain makes it ideal for battery operation. The output is typically 40 – 60 mV of audio signal. Optimal AGC is provided by R3 and C2 (see Figure 2). R3 (the AGC resistor) should be in the range 100R to 1.5K. A bandwidth of about 4kHz is achieved.
Download the MK484 datasheet:
The MK484 is now a discontinued IC. It was made by New Japan Radio although it does not appear anywhere on their website(s). You may try to find the equivalent IC for MK484.
Download the complete explanation of this AM radio receiver circuit: