Low-power microwave transmitters can be thwarted by tree branches or even heavy rain or snow. The presence of objects that are not in direct line of sight can cause diffraction effects that disrupt radio transmissions. For best propagation, a volume known as the first Fresnel zone should be free of obstructions.

Radiation reflected from the surrounding ground surface or salt water can also cancel out or enhance the direct signal. This effect can be reduced by raising one or both antennas further from the ground: the reduction in loss achieved is known as height gain.

See also Non-line-of-sight for more information on propagation impairments.

It is important to take into account the curvature of the Earth for the calculation of line-of-sight routes from maps, when a direct visual correction cannot be made. Microwave designs previously used a ⁄ Earth radius to calculate clearances along the path.

Although the frequencies used by mobile phones are in line-of-sight range, they still work in cities. This is possible thanks to a combination of the following effects:.

The combination of all these effects makes the mobile phone propagation environment very complex, with multipath effects and extensive Rayleigh fading. For mobile phone services, these issues are addressed by:.

A Faraday cage consists of a conductor that completely surrounds an area on all sides, top and bottom. Electromagnetic radiation is blocked when the wavelength is longer than any space. For example, cell phone signals are blocked in windowless metal enclosures that resemble a Faraday cage, such as elevator cabins and parts of trains, cars, and ships. The same problem can affect signals in buildings with extensive steel reinforcement.

Contenido

El horizonte radioeléctrico") es el lugar geométrico de los puntos en los que los rayos directos de una antena son tangenciales a la superficie de la Tierra. Si la Tierra fuera una esfera perfecta sin atmósfera, el horizonte radioeléctrico sería un círculo.

El horizonte radioeléctrico de las antenas transmisora y receptora "Radio (receptor)") se puede sumar para aumentar el rango de comunicación efectivo.

La propagación de ondas de radio se ve afectada por las condiciones atmosféricas, la absorción ionosférica") y la presencia de obstrucciones, por ejemplo, montañas o árboles. Fórmulas simples que incluyen el efecto de la atmósfera dan el rango como:.

Las fórmulas simples brindan una aproximación del mejor de los casos de la distancia máxima de propagación, pero no son suficientes para estimar la calidad del servicio en cualquier ubicación.

Earth bulge

In telecommunications, Earth bulge refers to the effect of the Earth's curvature on radio propagation. It is a consequence of a circular segment of the Earth's profile that blocks long-distance communications. Since the line of sight of the vacuum passes at different heights above the Earth, the propagating radio wave encounters slightly different propagation conditions along the way.

Distance from void to horizon

To overcome physical obstacles, devices such as passive reflectors or repeaters are used. "Bounces" or certain implementations such as MIMO-OFDM can also help, although they require a case-by-case analysis. In general, the simplest thing is to work on the height of the antennas, which increases the line of sight according to the Pythagorean theorem. Assuming the Earth is a perfect sphere and without atmospheric refraction, if R is the radius of the Earth and h is the altitude of the transmitting antenna, the distance of this station from the horizon is given by:.

Because the height of the station is much smaller than the radius of the Earth, the above formula can be approximated by:.

If the height is given in meters and the distance in kilometers,[1]​.

If the height is given in feet and the distance in statute miles,.

Thus, an antenna located at the top of a 100 m high tower or mast will have line of sight up to approximately 35 km. Reception of radio waves above this distance will be difficult, if not impossible. Added to the line-of-sight limitation are other effects such as free space attenuation, receiver sensitivity, interference, among others that reduce the range.

atmospheric refraction

The usual effect of the decreasing pressure of the atmosphere with height (variation of vertical pressure") is to bend (refract) radio waves towards the Earth's surface. This results in an effective radius of the Earth, "a convenient fiction that makes straight the actual curved path of a radio ray in the atmosphere by presenting it relative to an imaginary Earth with a larger radius" increased by a factor of about ⁄.[2]​[3]​[4]​[5]​ This factor k may change from its average value depending on the climate.

The above vacuum distance analysis does not consider the effect of the atmosphere on the propagation path of RF signals. In fact, RF signals do not propagate in straight lines: due to the refraction effects of atmospheric layers, the propagation paths are somewhat curved. Therefore, the maximum service range of the station is not equal to the line-of-sight vacuum distance. Typically, a factor k is used in the above equation, modified to be.

k > 1 means geometrically reduced bulge and longer service range. On the other hand, k < 1 means a shorter service range.

Under normal weather conditions, k is usually chosen[6]​to be ⁄. That means the maximum service range increases by 15%.

for h in meters and d in kilometers; either.

for h in feet and d in miles.

But in stormy weather, k may decrease and cause fading in the transmission. (In extreme cases, k may be less than 1). That is equivalent to a hypothetical decrease in the Earth's radius and an increase in the Earth's bulge.[7]​.

For example, under normal meteorological conditions, the service range of a station at an altitude of 1500 m with respect to receivers at sea level can be found as,.

Low-power microwave transmitters can be thwarted by tree branches or even heavy rain or snow. The presence of objects that are not in direct line of sight can cause diffraction effects that disrupt radio transmissions. For best propagation, a volume known as the first Fresnel zone should be free of obstructions.

Radiation reflected from the surrounding ground surface or salt water can also cancel out or enhance the direct signal. This effect can be reduced by raising one or both antennas further from the ground: the reduction in loss achieved is known as height gain.

See also Non-line-of-sight for more information on propagation impairments.

It is important to take into account the curvature of the Earth for the calculation of line-of-sight routes from maps, when a direct visual correction cannot be made. Microwave designs previously used a ⁄ Earth radius to calculate clearances along the path.

Although the frequencies used by mobile phones are in line-of-sight range, they still work in cities. This is possible thanks to a combination of the following effects:.

The combination of all these effects makes the mobile phone propagation environment very complex, with multipath effects and extensive Rayleigh fading. For mobile phone services, these issues are addressed by:.

A Faraday cage consists of a conductor that completely surrounds an area on all sides, top and bottom. Electromagnetic radiation is blocked when the wavelength is longer than any space. For example, cell phone signals are blocked in windowless metal enclosures that resemble a Faraday cage, such as elevator cabins and parts of trains, cars, and ships. The same problem can affect signals in buildings with extensive steel reinforcement.

Contenido

El horizonte radioeléctrico") es el lugar geométrico de los puntos en los que los rayos directos de una antena son tangenciales a la superficie de la Tierra. Si la Tierra fuera una esfera perfecta sin atmósfera, el horizonte radioeléctrico sería un círculo.

El horizonte radioeléctrico de las antenas transmisora y receptora "Radio (receptor)") se puede sumar para aumentar el rango de comunicación efectivo.

La propagación de ondas de radio se ve afectada por las condiciones atmosféricas, la absorción ionosférica") y la presencia de obstrucciones, por ejemplo, montañas o árboles. Fórmulas simples que incluyen el efecto de la atmósfera dan el rango como:.

Las fórmulas simples brindan una aproximación del mejor de los casos de la distancia máxima de propagación, pero no son suficientes para estimar la calidad del servicio en cualquier ubicación.

Earth bulge

In telecommunications, Earth bulge refers to the effect of the Earth's curvature on radio propagation. It is a consequence of a circular segment of the Earth's profile that blocks long-distance communications. Since the line of sight of the vacuum passes at different heights above the Earth, the propagating radio wave encounters slightly different propagation conditions along the way.

Distance from void to horizon

To overcome physical obstacles, devices such as passive reflectors or repeaters are used. "Bounces" or certain implementations such as MIMO-OFDM can also help, although they require a case-by-case analysis. In general, the simplest thing is to work on the height of the antennas, which increases the line of sight according to the Pythagorean theorem. Assuming the Earth is a perfect sphere and without atmospheric refraction, if R is the radius of the Earth and h is the altitude of the transmitting antenna, the distance of this station from the horizon is given by:.

Because the height of the station is much smaller than the radius of the Earth, the above formula can be approximated by:.

If the height is given in meters and the distance in kilometers,[1]​.

If the height is given in feet and the distance in statute miles,.

Thus, an antenna located at the top of a 100 m high tower or mast will have line of sight up to approximately 35 km. Reception of radio waves above this distance will be difficult, if not impossible. Added to the line-of-sight limitation are other effects such as free space attenuation, receiver sensitivity, interference, among others that reduce the range.

atmospheric refraction

The usual effect of the decreasing pressure of the atmosphere with height (variation of vertical pressure") is to bend (refract) radio waves towards the Earth's surface. This results in an effective radius of the Earth, "a convenient fiction that makes straight the actual curved path of a radio ray in the atmosphere by presenting it relative to an imaginary Earth with a larger radius" increased by a factor of about ⁄.[2]​[3]​[4]​[5]​ This factor k may change from its average value depending on the climate.

The above vacuum distance analysis does not consider the effect of the atmosphere on the propagation path of RF signals. In fact, RF signals do not propagate in straight lines: due to the refraction effects of atmospheric layers, the propagation paths are somewhat curved. Therefore, the maximum service range of the station is not equal to the line-of-sight vacuum distance. Typically, a factor k is used in the above equation, modified to be.

k > 1 means geometrically reduced bulge and longer service range. On the other hand, k < 1 means a shorter service range.

Under normal weather conditions, k is usually chosen[6]​to be ⁄. That means the maximum service range increases by 15%.

for h in meters and d in kilometers; either.

for h in feet and d in miles.

But in stormy weather, k may decrease and cause fading in the transmission. (In extreme cases, k may be less than 1). That is equivalent to a hypothetical decrease in the Earth's radius and an increase in the Earth's bulge.[7]​.

For example, under normal meteorological conditions, the service range of a station at an altitude of 1500 m with respect to receivers at sea level can be found as,.