Coverage map
Encyclopedia
Coverage maps are designed to indicate the service areas of radio
communication transmitting stations. Typically these may be produced for radio
or television
stations, for mobile telephone
networks and for satellite
networks. Such maps are alternatively known as propagation
maps. For satellite
networks, a coverage map is often known as a footprint
.
) / Band II, the BBC
defines the service area boundary as corresponding to an average field strength
of 54 dB
(relative to 1 µV/m) at a height of 10 m above ground level.
/ Mediumwave
, the BBC
defines the daytime service area boundary as a minimum field strength of 2 mV/m. At night, the service area of mediumwave services can be drastically reduced by co-channel interference
from distant stations.
antennas
, or simply being located on high ground can yield good signal strengths well outside the indicated area.
The significance of local geographical conditions cannot be over emphasised and this was underlined by an experiment which revealed the signal reception conditions around a typical house. The site did not have the critical "line-of-sight propagation
" to the transmitter. Average signal levels, taken at the same height, varied by up to 6dB, and for individual frequencies by up to 14dB. In RF reception terms these figures are huge differences.
Although carriers
and broadcasters
attempt to design their networks to eliminate dead zones, no network is perfect, so coverage breaks within the general coverage areas are still possible.
Often companies will construct low power satellite stations to fill in bad reception areas that become apparent once the high power transmitter's coverage map has identified where the network is deficient.
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...
communication transmitting stations. Typically these may be produced for radio
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...
or television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
stations, for mobile telephone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
networks and for satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
networks. Such maps are alternatively known as propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
maps. For satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
networks, a coverage map is often known as a footprint
Footprint (satellite)
The footprint of a communications satellite is the ground area that its transponders offer coverage, and determines the satellite dish diameter required to receive each transponder's signal...
.
Definition of coverage
Typically a coverage map will indicate the area within which the user can expect to obtain good reception of the service in question using standard equipment under normal operating conditions. Additionally, the map may also separately denote supplementary service areas where good reception may be obtained but other stations may be stronger, or where reception may variable but the service may still be usable.Technical details
The field strength that the marked service boundary on a coverage map represents will be defined by whoever produces the map, but typical examples are as follows:VHF(FM) / Band II
For VHF(FMFrequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
) / Band II, the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
defines the service area boundary as corresponding to an average field strength
Field strength
In physics, the field strength of a field is the magnitude of its vector value.In theoretical physics, field strength is another name for the curvature form...
of 54 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(relative to 1 µV/m) at a height of 10 m above ground level.
MF / Mediumwave
For MFMedium frequency
Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
/ Mediumwave
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...
, the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
defines the daytime service area boundary as a minimum field strength of 2 mV/m. At night, the service area of mediumwave services can be drastically reduced by co-channel interference
Co-channel interference
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same frequency. There can be several causes of co-channel radio interference; four examples are listed here....
from distant stations.
Limitations
Often coverage maps show general coverage for large regions and therefore any boundary indicated should not be interpreted as a rigid limit. The quality of reception can be very different at places only short distances apart, and this phenomenon is more apparent as the transmission frequency increases. Inevitably small pockets of poor reception may exist within the main service area that cannot be shown on the map due to scale issues. Conversely, the use of sensitive equipment, high gainGain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
antennas
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
, or simply being located on high ground can yield good signal strengths well outside the indicated area.
The significance of local geographical conditions cannot be over emphasised and this was underlined by an experiment which revealed the signal reception conditions around a typical house. The site did not have the critical "line-of-sight propagation
Line-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...
" to the transmitter. Average signal levels, taken at the same height, varied by up to 6dB, and for individual frequencies by up to 14dB. In RF reception terms these figures are huge differences.
Although carriers
Telephone company
A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...
and broadcasters
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
attempt to design their networks to eliminate dead zones, no network is perfect, so coverage breaks within the general coverage areas are still possible.
Often companies will construct low power satellite stations to fill in bad reception areas that become apparent once the high power transmitter's coverage map has identified where the network is deficient.