Simple AM Radio Receiver
Build a complete AM radio receiver from scratch using the MK484 IC
Project Overview
This advanced project teaches you to build a complete AM radio receiver from the ground up. You'll learn about RF circuit design, antenna theory, and the principles of radio frequency amplification and detection.
Advanced Concepts You'll Master:
- Radio frequency (RF) circuit design and impedance matching
- Antenna theory and construction techniques
- Tuned circuit design and resonance principles
- AM detection and audio recovery methods
- RF shielding and interference reduction
- Sensitivity and selectivity optimization
This is a receive-only device. Check local regulations regarding antenna installations.
Required Components
Specialized RF components for radio construction
Circuit Theory & Design
How AM Radio Works:
- • RF signals are captured by the ferrite rod antenna
- • Tuned circuit selects desired frequency
- • MK484 IC amplifies and detects the AM signal
- • Audio information is recovered and amplified
- • High-impedance output drives crystal earpiece
Key Design Principles:
- • Antenna resonance determines frequency coverage
- • Q factor affects selectivity vs sensitivity
- • Proper impedance matching maximizes signal transfer
- • Ground plane improves signal-to-noise ratio
- • RF decoupling prevents oscillation
Antenna Coil Specifications:
Primary winding: 60 turns of 0.2mm enameled wire, close-wound on 10cm ferrite rod
Antenna tap: Connection at 10th turn from ground end
Tuning range: 530-1710 kHz with 365pF variable capacitor
Coupling: Loose coupling to prevent loading and maintain Q
Step-by-Step Construction
Wind the antenna coil: 60 turns of 0.2mm wire on ferrite rod, tap at 10 turns
Install the MK484 IC on the PCB with proper orientation (check datasheet)
Connect the variable tuning capacitor across the main antenna coil
Wire the antenna tap to the IC input through a coupling capacitor
Connect the power supply with proper filtering and decoupling
Install the volume control potentiometer and output coupling
Connect the high-impedance earpiece or audio output jack
Test reception by tuning across the AM band (530-1710 kHz)
Optimize antenna orientation and tuning for best reception
Add RF gain control if needed for strong local stations
Troubleshooting Guide
No stations received
Check antenna coil connections, IC power supply, and proper grounding
Weak reception
Improve antenna (longer wire, better ground), check IC bias voltage
Poor selectivity
Adjust antenna coupling, add RF gain control, check tuning capacitor
Distorted audio
Reduce RF gain, check power supply filtering, verify IC connections
Oscillation/squealing
Improve power supply decoupling, separate input/output wiring, add bypass capacitors
Technical Specifications
Performance Optimization
Improving Reception:
- Orient ferrite rod antenna perpendicular to transmitter
- Add external wire antenna for weak stations (10-50 feet)
- Use good RF ground connection (cold water pipe, ground rod)
- Keep receiver away from computers and switching power supplies
- Use shielded enclosure to reduce electrical interference
Advanced Modifications:
- Add RF gain control for strong signal handling
- Include audio amplifier stage for speaker operation
- Add bandwidth control for better selectivity
- Implement AGC (Automatic Gain Control) circuit
- Add S-meter for signal strength indication
Success Criteria: Clear reception of local AM stations with good audio quality and stable tuning across the entire AM band.