The Story of Hertz-Hz, MHz (Megahertz), and GHz (Gigahertz)

Heinrich Hertz
Heinrich Hertz. Ullstein Bild / Getty Images

In wireless communications, the term "Hz" (pronounced Hertz after the name of 19th century scientist Heinrich Hertz) refers to the transmission frequency of radio signals in cycles per second:

  • 1 Hz equals one cycle per second
  • 1 MHz (Megahertz) equals one million cycles per second (or 1 million Hz)
  • 1 GHz (Gigahertz) equals one billion cycles per second (or 1000 MHz).

Wireless computer networks operate at different transmission frequencies depending on the technology they use.

Wireless networks also operate over a range of frequencies called a band rather than one exact frequency number.

A network that uses higher-frequency wireless radio communication does not necessarily offer faster speeds than lower-frequency wireless networks.

2.4 GHz and 5 GHz Wi-Fi

Wi-Fi networks all operate in either 2.4 GHz or 5 GHz bands. These are ranges of radio frequency open for public communication (i.e., unregulated) in most countries.

The 2.4 GHz Wi-Fi bands range from 2.412 GHz on the low end to 2.472 GHz on the high end (with one additional band having limited support in Japan). Starting with 802.11b and up to the latest 802.11ac, 2.4 GHz Wi-Fi networks all share these same signal bands and are compatible with each other.

Wi-Fi began utilizing 5 GHz radios starting with 802.11a although their mainstream use in homes started only with 802.11n. The 5 GHz Wi-Fi bands range from 5.170 to 5.825 GHz, with some lower bands additionally supported in Japan only).

Other Types of Wireless Signaling

Beyond Wi-Fi, consider these other examples of wireless communications:

  • traditional cordless phones operated in a 900 MHz range, as does the newer 802.11ah standard
  • Bluetooth network connections utilize 2.4 GHz signaling similar to Wi-FI, but Bluetooth and Wi-Fi are imcompatible

Why so many different variations? For one, different types of communcations must use separate frequencies to avoid colliding with each other. In addition, higher frequency signals such as 5 GHz can carry larger amounts of data (but in return have greater restrictions on distance and require more power to penetrate obstructions).