Radial (radio)
In RF engineering
RF engineering
Radio frequency engineering is a subset of electrical engineering that deals with devices that are designed to operate in the Radio Frequency spectrum...

, radial has two different meanings, both referring to lines which radiate from (or intersect at) a radio antenna.


In the field of planning, radials are evenly-spaced point
-Business and finance:* Basis point, 1/100 of one percent, denoted bp, bps, and ‱* Pivot point, a price level of significance in analysis of a financial market that is used as a predictive indicator of market movement...

s (vectors) along evenly-spaced line
- Science and technology :* Line , a circuit or loop.** A power line for electric power transmission** line power or lines power, domestic mains electricity.** telephone line** RF transmission line...

s (bearing
Bearing (navigation)
In marine navigation, a bearing is the direction one object is from another object, usually, the direction of an object from one's own vessel. In aircraft navigation, a bearing is the actual compass direction of the forward course of the aircraft...

s) from a common point on a map
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

, which are used to determine the average
In mathematics, an average, or central tendency of a data set is a measure of the "middle" value of the data set. Average is one form of central tendency. Not all central tendencies should be considered definitions of average....

The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....

 above mean sea level
Above mean sea level
The term above mean sea level refers to the elevation or altitude of any object, relative to the average sea level datum. AMSL is used extensively in radio by engineers to determine the coverage area a station will be able to reach...

 (AMSL) within a radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 station's broadcast range (including broadcast station
Broadcast station
A broadcast station may be:*a radio station*a television stationIt does not include radio networks or television networks.-See also:*Broadcasting*Broadcast network*Station...

s and cellphone base station
Base station
The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...

s, among others). This in turn determines the station's height above average terrain
Height above average terrain
Height above average terrain is used extensively in FM radio and television, as it is actually much more important than effective radiated power in determining the range of broadcasts...

 (HAAT), which greatly affects its coverage area (more so than effective radiated power
Effective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...

), and therefore the potential for RF interference with other adjacent stations or cells. This information must be submitted with an application for a construction permit
Construction permit
A construction permit or building permit is a permit required in most jurisdictions for new construction, or adding on to pre-existing structures, and in some cases for major renovations. Generally, the new construction must be inspected during construction and after completion to ensure compliance...

. The points used for calculation may differ if a directional antenna
Directional antenna
A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....

 is used.


Stations at low frequencies like shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...

, and especially the mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...

In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...

 AM broadcasting
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...

 bands, require grounding or earthing wires to be buried in the soil in a radial pattern, in order to have a proper ground plane
Ground plane
In electrical engineering, a ground plane is an electrically conductive surface.-Radio antenna theory :In telecommunication, a ground plane structure or relationship exists between the antenna and another object, where the only structure of the object is a structure which permits the antenna to...

 for the large mast radiator
Mast radiator
A mast radiator is a radio mast or tower in which the whole structure itself functions as an antenna. This design is commonly used for transmitting antennas operating at low frequencies, in the VLF, LF and MF ranges, in particular those used for AM broadcasting. The metal mast is electrically...

s used as radio antennas at their long wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

s. These wires are also called radials, ground radials, grounding radials, or earthing radials. All metal objects within the near field
Near field
Near field may refer to:*Near-field , an algebraic structure*Near and far field, parts of an electromagnetic field*Near field communication, a set of short-range wireless technologies, typically requiring a distance of 4 cm or less...

 of the radiator must also be tied to this system, or they will be energized with radio-frequency energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

, and become an electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....

 hazard, as well as potentially affecting or distorting the antenna pattern as a parasitic radiator. In one unusual case, the strip mall
Strip mall
A strip mall is an open-area shopping center where the stores are arranged in a row, with a sidewalk in front. Strip malls are typically developed as a unit and have large parking lots in front...

 built around the WSB
WSB — branded AM 750 and 95.5 FM News/Talk WSB — is a commercial radio station licensed to Atlanta, Georgia broadcasting a news/talk format. The station transmits with 50,000 watts of nondirectional power day and night, enjoying clear-channel status on its broadcast frequency according to the U.S...

 AM tower near Atlanta
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...

 has every metal object (such as plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

 and duct
A duct may refer to:* Duct , various ducts in anatomy and physiology* Duct , for transfer of air between spaces in a structure* Duct tape, a kind of adhesive tape* Ducted fan, motor for aircraft...

work) grounded for this reason.
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