In US

broadcasting Broadcasting is the data distribution, distribution of sound, audio audiovisual content to dispersed audiences via a electronic medium (communication), mass communications medium, typically one using the electromagnetic spectrum (radio waves), ...

, service contour (or protected contour) refers to the area in which the

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...

(FCC) predicts coverage. The FCC calculates FM and TV contours based on

effective radiated power Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would ha ...

(ERP) in a given direction, the radial

height above average terrain Height above average terrain (HAAT), or (less popularly) effective height above average terrain (EHAAT), is the vertical position of an antenna site above the surrounding landscape. HAAT is used extensively in FM radio and television, as it is ...

(HAAT) in a given direction, the FCC's propagation curv

and the station's List of broadcast station classes, class. AM contours are based on the standard

ground wave Ground wave is a mode of radio propagation that consists of currents traveling through the earth. Ground waves propagate parallel to and adjacent to the surface of the Earth, and are capable of covering long distances by diffracting around the E ...

field strength pattern, the

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

, and the

ground conductivity Ground conductivity refers to the electrical conductivity of the subsurface of the earth. In the International System of Units (SI) it is measured in millisiemens per meter (mS/m). Radio propagation Ground conductivity is an extremely important ...

in the area. While the FCC makes FM and TV service contour data readily available, the AM, while unavailable as a separate data file, can be obtained through a
AM Query
in the resulting 'maps' section of each record (when using the 'detailed output' output option).

External links

FM Database protected contour maps (Official)

Plot predicted AM/FM coverage patterns (unofficial)
{{Comm-stub Broadcast engineering