This AM radio receiver circuit with earphone is a saving version that use a few parts, cheap , easy to build and Suitable to be assembled to study.
We come to understand the principles of the AM radio before. The Radio can receive a radio wave signals also must there are a radio frequency transmission station. The station does not send out the a sound wave that we talked. The station will produce the kind of wave called a carrier wave. This carrier wave conductor of sound waves that we listened to the our radio receivers.
The station must be mixed between the carrier and sound waves before. By this sound wave is converted as electrical signal by the microphone. And the signals are mixed together by the height of the wave. The height of the waves is not constant. But frequency is fixed see Figure 1.
Figure 1 The characteristics mixing waves on AM radio system.
Wave that mixed. Will be sent out by the station’s antenna. We have used this system for AM radio receivers only. And we can choose the frequency of each station with simple This behavior as shown in Figure 1.
The signal is selected by the receiver. Waves will be forwarded to sectors expansion wave. Which is responsible for the signal to be strong enough to use it. The increase wave section may be have several sector. When the signal is sent through the increase wave section, will into the separate wave sectors. Which act separated the carrier wave signal from the audio signal. This signal is Characteristics same signal from the microphone of a radio station, and then can be extended by Amplifier in order to have the strength enough to be used with headphones or speakers.
Use power supply of 3 Vdc.
Maximum consumption current about 45 mA
PCB size : 2.38 x 1.24 inch.
How does it work.
A circuit diagram that shown in Figure 1 IC1 MK484 acts as receiver system by have variable capacitor and OSC coil as frequency adjusting of each station. The IC’s OUTPUT will be connected to C3 to increase signal up by TR1 and TR2 sent to speaker .
Figure 1 the schematic diagram of AM radio receiver circuit
We use the general AM variable, The output is connected to a dynamic headphones or also small speakers. But impedance to 30 ohms up. The ANT point for the antenna.
The connecting to speaker SP point. Then apply 3V DC power supply to the circuit. The positive polarity to +3V point and the negative polarity to the G. Then we will hear sound on earphone. Radio station signal. But if can receive a few station. You can adjust the OSC coil and move ANT to antenna.
How to build
This project have a few we can assemble them on a universal PCB or solder on PCB as components layout and wiring in Figure 2
Figure 2 the components layout and wiring.
and Figure 3 is complete projects
The parts list
R5: 27 ohm
C1, C3, C4____103 or 0.01uF
C2: 104 or 0.1uF
IC1: MK484 or TA7642
TR1, TR2: C458, C828, C945, C1815
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