In US

broadcasting Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a one-to-many model. Broadcasting began ...

, 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 federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisd ...

(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 ...

(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 is above the surrounding landscape. HAAT is used extensively in FM radio and television, as it ...

(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 waves are radio waves propagating parallel to and adjacent to the surface of the Earth, following the curvature of the Earth. This radiation is known as Norton surface wave, or more properly Norton ground wave, because ground waves in rad ...

field strength pattern, the

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from '' angular frequency''. Frequency is measured in hertz (Hz) which is ...

, 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 importan ...

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