A channel is a specific frequency band used for communication. It is a slice of the spectrum allocated to a particular transmission. A radio station broadcasts on a channel. A Wi-Fi router uses a channel. A TV station occupies a channel. Channels keep signals from interfering with each other.

In radio, channels are defined by frequency. AM radio channels are 10 kHz apart. FM channels are 200 kHz apart. TV channels are 6 MHz wide in the U.S. Wi-Fi channels are 20 MHz wide, though they can be bonded to 40, 80, or 160 MHz for more speed. Cellular channels vary by band and technology.

Channel concepts

• Frequency: the center of the channel
• Bandwidth: how wide the channel is
• Guard band: unused spectrum between channels
• Interference: signals overlapping
• Channel bonding: combining channels for speed

Channels are a shared resource. Governments allocate them. Engineers manage them. Users compete for them. In Wi-Fi, crowded channels slow everyone down. In cellular, carriers pay billions for licenses. The channel is the container. The signal is the content.