Radio frequency

Description

A portion of the electromagnetic spectrum containing wave frequencies from about 3 kilohertz (100,000 m) to about 3 gigahertz (1 cm). Radio frequencies (RF) are used for radio, television, and cellular phone transmissions. Information is encoded on a carrier wave via a modulation process that involves varying amplitude, frequency, or duration. Except for the highest frequencies, the pulses of radio energy transmitted vertically upward are reflected and refracted back to earth by the ionosphere layer. Thus the signals can be sent beyond the line of sight. Frequency designations and their uses are listed below:

• Very low frequencies (vlf) 3-30 kilohertz: time signals
• Low frequencies (lf) 30-300 kilohertz: maritime mobile, navigational, radio
• Medium frequencies (mf) 300-3,000 kilohertz: maritime mobile, radio
• High frequencies (hf, short-waves) 3-30 megahertz: fixed, mobile, radio, maritime, aeronautical, amateur
• Very high frequencies (vhf) 30-300 megahertz: fixed, mobile, radio, television, maritime, aeronautical
• Ultrahigh frequencies (uhf) 300-3,000 megahertz: fixed, mobile, television, maritime, aeronautical, radio location, meterorlogical, space communication
• Superhigh frequencies (shf) 3-30 gigahertz: fixed, mobile, radio location, space and satellite communication

Synonyms and Related Terms

radio-frequency; RF