Amplitude modulation (AM) on your radio works by embedding the sound information, like a user's voice, into a constant radio wave. This is done by changing the height (amplitude) of the radio wave according to the sound being transmitted.
Understanding Amplitude Modulation
Radio broadcasting needs a way to send sound (like music or voice) over long distances using radio waves. Sound itself vibrates relatively slowly. Radio waves, however, vibrate very quickly and can travel far. Amplitude Modulation is a technique to combine these two.
The Carrier Wave and the Input Signal
At the heart of AM are two components:
- The Carrier Wave: This is a high-frequency radio wave generated by the radio transmitter. Think of it as the vehicle carrying the information. It has a constant frequency and amplitude before modulation.
- The Input Signal: This is the sound you want to transmit (e.g., someone's voice). It's an electrical signal whose strength (amplitude) varies with the loudness and pitch of the sound.
How Modulation Happens
According to the reference, amplitude modulation occurs when:
- A carrier wave's height (amplitude) is adjusted.
- An input signal's height varies with the loudness of something like a user's voice.
- This input signal is added to the carrier.
- As a result, the carrier's amplitude changes corresponding to the input signal that's been fed into it.
This process where the carrier's amplitude is varied by the input signal is called amplitude modulation or AM.
Essentially, the peaks and troughs of the audio signal are used to modify the amplitude of the much higher frequency carrier wave. When the audio signal is strong (loud), the carrier wave's amplitude becomes larger. When the audio signal is weak (quiet), the carrier wave's amplitude becomes smaller. The frequency of the carrier wave itself remains constant.
The Result: The AM Signal
The output of this process is the AM signal. This modulated wave now contains the original audio information within its varying amplitude. This is the wave that is then broadcast from the radio transmitter antenna.
Demodulation at the Radio Receiver
Your radio receiver picks up this AM signal. It then performs a process called demodulation or detection. The receiver basically strips away the high-frequency carrier wave and recovers the original audio signal by detecting the changes in the amplitude. This recovered audio signal is then sent to the speaker, which converts it back into sound that you can hear.
Summary Table
Here’s a simple breakdown:
| Component | Role | Characteristics (Simplified) |
|---|---|---|
| Carrier Wave | The high-frequency "carrier" for information | Constant high frequency, constant amplitude (initially) |
| Input Signal | The sound information (voice, music) | Low frequency, amplitude varies with sound |
| AM Signal | The transmitted wave | High frequency (same as carrier), amplitude varies with input signal |
AM is a fundamental technique used in many radio communication systems, notably for the AM broadcast band on your radio dial.
