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Discuss how longwave (LW), shortwave (SW) and microwave links can be used to communicate beyond the visible horizon - AQA - A-Level Physics - Question 5 - 2017 - Paper 8
Question 5
Discuss how longwave (LW), shortwave (SW) and microwave links can be used to communicate beyond the visible horizon. For each link, you should give: - a typical ca... show full transcript
Worked Solution & Example Answer:Discuss how longwave (LW), shortwave (SW) and microwave links can be used to communicate beyond the visible horizon - AQA - A-Level Physics - Question 5 - 2017 - Paper 8
Step 1
Longwave (LW)
Answer
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Typical Carrier Frequency: The frequency for longwave communication typically ranges from about 150 kHz to 300 kHz.
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Signal Transmission: For longwave signals, they travel by following the curvature of the Earth. The signals are reflected and refracted by the ground surface which allows them to cover long distances despite being below the radio horizon.
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Typical Use: Longwave signals are often used in broadcasting national radio signals.
Step 2
Shortwave (SW)
Answer
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Typical Carrier Frequency: Shortwave communication generally uses frequencies between 3 MHz and 30 MHz.
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Signal Transmission: Shortwave signals can reflect off the ionosphere, which is a layer of the Earth's atmosphere. This allows them to travel over the horizon, bouncing back towards the Earth at distant locations.
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Typical Use: Shortwave is used for international broadcasting, allowing for coverage over vast distances, particularly for communication with ships and in areas where ground-based signals might fail.
Step 3
Microwave
Answer
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Typical Carrier Frequency: Microwaves use frequencies approximately between 1 GHz and 100 GHz.
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Signal Transmission: Microwaves require line-of-sight transmission. The signals are transmitted in straight lines and are sensitive to obstacles, which means repeaters are often necessary to extend coverage over longer distances.
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Typical Use: Microwave links are commonly used for satellite communications and terrestrial microwave networks, facilitating reliable data transfer for various applications including internet services.