The medium frequency band sits between 300 kHz and 3 MHz with wavelengths of 1 km and 100 m respectively. One of the most popular applications using this frequency range is AM radio. AM radio is based on technology developed in the early 1900s and saw widespread adoption in the 1920s.

Have you ever listened to the radio and wondered what the number representing the radio station meant? In Toronto, Canada, for example, there is a radio station on the AM band called 680 News. The 680 actually refers to the frequency that is used to broadcast this station, 680 kHz:

The AM in AM radio stands for amplitude modulation, a method of modulating a radio wave where the amplitude of the carrier wave is modulated proportionally to the message signal. As we can see in the preceding diagram, the Amplitude Modulator modulates the carrier wave based on the sound coming from the sound source (microphone).

AM radio broadcasts in the 535 kHz to 1605 kHz range with stations assigned from 540 kHz in intervals of 10 kHz.