Definition: 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 MHz (Megahertz) equals one million cycles per second, while 1 GHz (Gigahertz) equals one billion cycles per second or 1000 MHz.
Bluetooth and WiFi networks signal in the ranges of 2.4 GHz or 5 GHz. These are bands of radio frequency open for public communication (i.e., unregulated) in most countries. WiMax wireless networks use a much larger range of GHz frequencies. A higher frequency such as 5 GHz requires more power to penetrate obstructions than a lower frequency like 2.4 GHz.