Wave Propagation Flashcards
Wave length from a weather radar
9 GHz
Factors that effect wave propagation
Weather Ionosphere Altitude Terrain Curvature of the earth Power Obstacles Solar activity Type of antenna/wave
The effect of reflection
The wave will become weaker when it bounces off objects
-water, atmosphere, hills
Effect of refraction
As it passes through a median it changes direction
The effect of diffraction
The ability of the wave to follow the curvature of the earth
A higher wave length will make this easier
The effect of absorption
The wave being absorbed by a median and getting weaker when doing so (attenuation) - degrading the waves energy
Water
The effect of interference
Occurs when 2 or more signals with similar wave freq interfere with each other
If the reflected signal arrives out of phase it will attenuate it and produce noise
If it arrives in anti phase, the wave will be completely be cancelled out
3 categories of waves
Ground/surface
Sky
Space
Ground/surface waves
Low freq
More likely to follow the curvature of the earth
Sky waves
Refract from the ionosphere
Bounces back of the surface
Mid freq
Space waves
Line of sight - only travels in a straight line
High freq
VHF
Critical angle - LF propagation
Angle at which the sky gets refracted by the ionosphere.
Highest angle at which an emission returns to earth is called the critical angle
Distance between the returning sky waves and the last usable surface wave
Dead space/ null zone
Min skip distance
Distance between the returning sky waves and the aerial
Effect of the ionosphere on LF propagation
Thickest durning the day as it gets more solar radiation, refracts more
Thinner during the night, absorbs more
