What is super refraction and duct propagation?
What is super refraction and duct propagation?
Duct propagation is sometimes referred as super refraction. It allows the propagation of the signals beyond the horizon. This means that, unlike surface wave propagation, it permits the signal transmission without assuring the need for having a line of sight distance between the two antennas.
What is super refraction and sub refraction?
Sub-refractive atmospheric conditions occur when the refractivity gradient has a significantly larger value, super-refractive conditions occur when the refractivity gradient is well below the standard value of -40 N-units/km.
What is ducting in microwave?
This condition, called superrefraction or ducting, causes the curvature of radio rays to exceed the curvature of the earth’s surface. This effect can trap or reflect radio waves. If refractivity increases with height near the earth, a positive refractive gradient condition called subrefraction exists.
What is the definition of duct propagation?
A layer of troposphere bounded above and below by layers that have different refractive index, which confines and propagates an abnormally high proportion of VHF (very high frequency) and UHF (ultrahigh frequency) radiation.
What is Owf in antenna?
The frequency, which is being used mostly for a particular transmission and which has been predicted to be used over a particular period of time, over a path, is termed as Optimum Working Frequency (OWF).
What is MUF in antenna?
In radio transmission maximum usable frequency (MUF) is the highest radio frequency that can be used for transmission between two points via reflection from the ionosphere (skywave or “skip” propagation) at a specified time, independent of transmitter power.
What is radar attenuation?
Radar attenuation is simply the absorption or reflection of radar signals as the radar pulse penetrates an area of precipitation, preventing that radar from detecting any additional cells that lie behind the first storm.
What is evaporation duct?
The evaporation duct is a downward refracting layer that results from the rapid decrease in humidity with respect to altitude occurring in the atmospheric surface layer above bodies of water. The evaporation duct affects radar detection ranges at frequencies of approximately 1 GHz and above.
What is thermal ducting?
Ventilation systems require thermal insulation in order to restrict and control heat loss. For financial and environmental reasons, it is important you reduce unnecessary heat loss in ducts that transport warm air. Ventilation ducts transport either warm or cold air.
What is a super-refraction?
In a super-refraction situation, the radar beam could be increasing at a lesser rate with height than normal as the beam moves away from the radar site or the beam could even be bending back down and getting closer to the earth’s surface in spite of the earth’s curvature.
What is radio refraction?
To understand refraction, which is the atmospheric bending of the radio path away from a straight line, we need to remember Snell’s law: Willebrord Snel van Royen (1580–1626) was a Dutch astronomer and mathematician and is most famous for his law of refraction, which is now known as “Snell’s law”.
What is the difference between refraction and scattering?
Scattering – from eddies in the air, from rain , from reflecting surfaces and objects Diffraction – from terrain, buildings and vegetation To understand refraction, which is the atmospheric bending of the radio path away from a straight line, we need to remember Snell’s law:
What is radar ducting?
It is ducting when the radar beam actually bends closer the earth’s surface with distance away from the radar. The bending could be strong enough for the radar beam to bounce off the earth’s surface.