Передатчик на 3 мГц с амплитудной модуляцией

Introduction

In this tutorial, we will explore how to build a 3 MHz amplitude modulation transmitter. This project is suitable for electronics enthusiasts interested in radio communication. We will guide you through the necessary components, assembly, and tuning processes to create your own transmitter.

Step 1: Gather Components

Before starting your project, ensure you have all the necessary components:

• Transistors: 2N3904 or similar for the oscillator circuit
• Resistors: 1kΩ, 10kΩ, and 100kΩ
• Capacitors: 10nF, 100nF, and a variable capacitor
• Inductor: 10µH coil
• Diodes: 1N4148 or similar
• Power Supply: 9V battery or DC power source
• Antenna: Suitable for 3 MHz operation

Step 2: Assemble the Circuit

Now that you have all your components, follow these steps to assemble the circuit:

1. Create the Oscillator Circuit:

   • Connect the transistor in a common emitter configuration.
   • Use a resistor (1kΩ) at the base to limit current.
   • Connect a capacitor (10nF) from the collector to the base for feedback.
   • Add the inductor (10µH) in parallel with the capacitor to set the frequency.

2. Set Up the Modulation Stage:

   • Use another transistor connected to the oscillator stage.
   • Connect the audio input (e.g., from a microphone) through a capacitor (100nF) to the base of the second transistor.
   • Ensure the collector is connected to the main output.

3. Output Stage:

   • Connect the output from the second transistor to the antenna.
   • Use a matching network if necessary to optimize transmission.

Step 3: Tune the Transmitter

Tuning is crucial for effective transmission. Follow these steps:

• Adjust the Variable Capacitor:

  • Tune the variable capacitor until you reach the desired frequency of 3 MHz.
  • Use a frequency counter or an oscilloscope to monitor the frequency.

• Test Modulation:

  • Connect a small speaker or an audio source to test the modulation.
  • Adjust the input levels to ensure clear audio transmission.

Step 4: Testing and Troubleshooting

Once assembled and tuned, it's time to test your transmitter:

• Check Signal Strength: Use an RF field strength meter to measure the signal.
• Identify Issues: If the signal is weak or distorted, check connections, component values, and tuning adjustments.
• Ensure Compliance: Make sure your transmitter complies with local regulations regarding broadcasting.

Conclusion

Congratulations on building your own 3 MHz amplitude modulation transmitter! This project not only enhances your understanding of electronics but also provides a practical application in radio communication. As next steps, consider experimenting with different modulation techniques or building a receiver to capture your transmissions.