Home / Topics / AC Circuits & EM Waves
Modulation (AM and FM)
Intermediate
Encoding information onto carrier waves.
Information is carried by varying a carrier's amplitude (AM) or frequency (FM). FM is more resistant to noise and AM has narrower bandwidth.
Digital schemes (QAM, OFDM) power Wi-Fi.
Demodulation recovers the signal.
In more detail
Amplitude modulation varies the amplitude of a carrier wave to carry information, while frequency modulation varies its frequency. FM is less affected by noise than AM.
Real-world uses
- AM radio uses amplitude modulation, while FM radio uses frequency modulation.
- Digital communication uses modulation schemes to encode bits.
- Radio stations use AM and FM to put speech and music onto a carrier wave for transmission.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why is FM better for music?
It resists amplitude noise and gives higher fidelity.
Why does AM reach further at night?
Its low-frequency signals reflect off the ionosphere.
Which is better, AM or FM?
FM is usually clearer and less affected by noise, while AM covers longer distances, especially at night.
Related topics in AC Circuits & EM Waves
Polarisation of EM waves · Antennas · Waveguides and transmission lines · Optical fibre communication · Radar · Lasers in communication