Crystal AM Transmitter

In this article, you will learn how to make AM transmitter easily. It is also know as AM radio station. It is one of the easiest electronics projects for engineers. Before getting started you have to know Amplitude Modulation.

Amplitude Modulation ( AM )

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In amplitude modulation, the amplitude (signal strength) of the carrier wave is varied in proportion to that of the message signal being transmitted. The message signal is, for example, a function of the sound to be reproduced by a loudspeaker, or the light intensity of pixels of a television screen. 

Amplitude modulation explanation

You can refer more about Amplitude Modulation here.

Parts required

  • R1- 10k
  • R2 -330k
  • R3- 1k
  • R4 – 15k
  • R5- 18 Ohms
  • C1 – 470uF/25v
  • C2, C3, C9- 0.1uf
  • C4 – 100uf/25v
  • C5, C6, C8 – 1nf
  • C7 – 100pf
  • D1, D2 – 1N4148
  • T1- BC548
  • T2- BC558
  • T3- BC547
  • T4- SL100
  • X1 – Modulation Transformer
  • Xtal – 10 MHz Crystal Oscillator
  • Microphone/ Audio In
  • S1- Switch

AM transmitter Circuit Diagram

AM Transmitter Circuit diagram

Working of AM transmitter Circuit

The working of this AM transmitter is divided into 3 stages.

  1. Getting Audio input and Amplification
  2. Amplitude modulation
  3. Transmission

At the first the audio signal is collected using microphone or audio jack (3.5mm). Since the audio signal is week and it is few milli volts, it cannot be transfer for longer distances. So it is to be amplified first. Here the amplification is done by transistors in the circuit. The amplified message signal is passed to modulation transformer.

After Amplification, we need to do modulation. It mean combining high frequency carrier signal with message signal. Here in the circuit the high frequency carrier signal is generated by 10MHz crystal oscillator. The high frequency signal generated by Crystal oscillator is passed to modulation transformer.

The message signal and carrier signal at modulation transformer undergoes amplitude modulation and resulting in AM signal.

The AM signal is transmitted into the air by the antenna with the help of LC oscillator.

The AM signal is collected by the AM receiver and demodulates the signal to extract the original message signal.

If you want to make FM Transmitter, you can check this amazing article How to make FM Transmitter.

If you have any quires regarding this project, please comment below. We will respond you ASAP.

Leave a Reply