|“||[t]he rate at which an electrical current alternates, usually measured in Hertz (Hz).||”|
Radio frequencies are described as multiples of hertz:
- kHz, kilohertz: thousand cycles per second;
- MHz, megahertz: million cycles per second;
- GHz, gigahertz: billion cycles per second.
Different frequencies have different natural properties: Lower frequencies travel farther and penetrate solids better, while higher frequencies can carry more information (faster data rates, etc.). The best balance of these properties for the purpose of cellphones is in the range of roughly 700-2,500 MHz. A specific range of frequencies allocated for a specific purpose is called a band.
Frequency is "number of occurrences of an event per defined period of time or number of trials."