Radio frequency is electromagnetic waves used for wireless communication. It spans from about 3 kHz to 300 GHz. Your phone, Wi-Fi, Bluetooth, garage door opener, and car key fob all use RF. The waves travel through air and walls. They carry data by varying amplitude, frequency, or phase.

Different frequencies behave differently. Low frequencies travel far and penetrate walls. High frequencies carry more data but have shorter range. Governments regulate the spectrum. In the U.S., the FCC assigns bands to broadcasters, telecoms, and unlicensed devices. Wi-Fi uses unlicensed bands at 2.4 GHz and 5 GHz.

Common RF bands

• AM radio: 530–1700 kHz
• FM radio: 88–108 MHz
• Wi-Fi: 2.4 GHz, 5 GHz, 6 GHz
• Bluetooth: 2.4 GHz
• 5G cellular: sub-6 GHz and mmWave

RF is invisible but crowded. Interference is a constant problem. As more devices connect, the spectrum gets tighter. Engineers use modulation, coding, and beamforming to squeeze more data into the same airwaves.