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11 Cards in this Set
- Front
- Back
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3 principal paths for Radio waves to travel between antennas |
- surface wave - sky wave - space wave |
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3 main methods of propagation and what two make up the 4th? |
- Surface wave - Sky wave - Space wave Ground waves are made up of the surface wave and the space wave |
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4 factors that increase radio wave range |
- increasing power output - using a more efficient antenna - using a more sensitive receiver - Reducing the amount of noise (interference) |
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Surface waves follow the earths surface due to ... |
Diffraction |
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Huygens Principle (Diffraction) (3) |
- All the points on a wave front can be looked at as a new source producing a wave front - These combine to produce a new wave front - This allows the wave to travel in shadow regions |
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Due to Huygens principle, surface waves can (2) |
- Pass around hills and other obstacles - follow the curvature of the earth |
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The main factors that determine the distance that a surface wave will travel are: (3) |
- Frequency of the radio wave - type of ground the wave travels over - position and polarisation of the antenna |
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The main factors that determine the distance that a surface wave will travel are: (3) |
- Frequency of the radio wave - type of ground the wave travels over - position and polarisation of the antenna |
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Types of ground and their effect on surface waves (6) |
Surface - Distance Jungle - Unusable Desert. - Poor Rocky terrain - Poor Flat, moist soil - Fair Bodies of fresh water - Fair Sea Water - Good |
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Best antenna position for a surface wave (2) |
Vertically polarised (attenuation) On a forward facing slope (no obstacles but EW protection) |
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Surface wave bands for military communication Surface wave bands for broadcasting |
Military (shorter range)- HF and VHF Broadcasting (longer range) VLF, LF and MF |
