What is a radio frequency?
Radio Frequency (RF) has no precise definition, but is commonly associated with electrical signals in the range of 30 Hertz (Hz) to 300 Gigahertz (GHz). This range covers AM and FM radio, broadcast television, satellite broadcasts and cellular communications.
However, engineers use the RF terminology for signals that are in this range of frequencies but not broadcast through the airwaves. Cable television, DVD players and even microprocessors in a personal computer all operate at RF frequencies. RF signals such as those found in radar systems and microwave ovens can carry a great deal of energy and may penetrate solid objects.
RF signals are common in many consumer applications such as remote controls for appliances. Because of their physical characteristics, some frequencies of RF signals radiate in many directions, and therefore do not require a direct line-of-sight between transmitter and receiver. Higher frequency RF signals will travel only in a line-of-sight but over great distances.
Cellular phone communications are RF frequencies that do not require line-of-sight, and can penetrate many solid objects. However, these signals only travel a short distance, usually no more than several miles. This characteristic allows each cellular tower to service a small area.
RF frequencies can interfere with each other. In the United States, the Federal Communications Commission (FCC) allocates specific frequency ranges of the RF radio spectrum to different uses such as broadcast television, emergency communications radio, cellular telephones and broadcast radio. The FCC also maintains blocks of unallocated bandwidth that are used for garage door openers, baby monitors and other consumer devices.
Radio frequency refers to an alternating electrical current with certain properties that allow it to be broadcast from an antenna. If the current generates an electromagnetic field or wave at a frequency that is suitable for broadcasting television or radio signals, then it is considered a radio frequency. These frequencies are part of the electromagnetic spectrum and are located just beyond the infrared side of visible light. Any frequency between about nine hertz — meaning nine cycles per second — and 300 gigahertz — meaning 300 billion cycles per second — can be considered a radio wave, although only frequencies near the middle of this range are used in actual radio broadcasts. The rest of the range of radio frequencies is used by military and scientific personnel, mostly. Most of us are familiar with AM and FM radio, but radios are only some of the wireless devices that use a radio frequency to operate. Television broadcasts received over the air are a form of radio waves, as a
