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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 typical carrier frequency for longwave links is in the range of 150 kHz to 300 kHz.
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Signal Travel Explanation: Longwave signals travel by ground wave propagation. This means that they follow the curvature of the Earth and can diffract around obstacles like buildings and hills. Ground waves are particularly effective for long distances, especially in areas with varying terrain.
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Typical Use: A common use of longwave communication is for national time signals, such as those used by radio stations.
Step 2
Shortwave (SW)
Answer
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Typical Carrier Frequency: Shortwave links typically operate in the frequency range of 3 MHz to 30 MHz.
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Signal Travel Explanation: Shortwave signals utilize skywave propagation, where signals are transmitted upwards and then reflected back to Earth by the ionosphere. This allows for long-distance communication, even beyond the horizon.
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Typical Use: Shortwave radios are commonly used for international broadcasting and to communicate with remote ships and on land-based systems.
Step 3
Microwave
Answer
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Typical Carrier Frequency: Microwave links operate at frequencies around 100 GHz to 2 GHz.
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Signal Travel Explanation: Microwave signals generally require line-of-sight propagation to travel effectively between transmitter and receiver. This means that the transmitting antenna needs to be visible to the receiving antenna without any obstacles in between. The signals can be affected by obstructions such as buildings, hills, or trees.
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Typical Use: Microwaves are extensively used for satellite communications and as a link for telephone networks.