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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
The typical carrier frequency for longwave links is around 150 kHz to 300 kHz.
Signals transmitted in this range travel by ground wave propagation, which means that they follow the curvature of the Earth. This is due to diffraction, allowing them to reach beyond the visual horizon.
A common application is in national time signals, such as those broadcast by the BBC in the UK.
Step 2
Shortwave (SW)
Answer
Shortwave links operate at carrier frequencies approximately between 3 MHz and 30 MHz.
These signals can be reflected off the ionosphere, which allows them to cover long distances and beyond the visual horizon, especially at night when ionospheric conditions are more favorable.
A typical use of shortwave is in amateur radio and broadcasts to remote areas, as it has long-range capabilities.
Step 3
Microwave
Answer
Microwave links operate at frequencies around 100 GHz to 2 GHz.
These signals typically require line-of-sight communication, due to their high frequency, which limits their ability to diffract around obstacles. However, when a clear line between transmitter and receiver is maintained, they can transmit large amounts of data efficiently.
Microwave communication is commonly used in satellite TV broadcasts and telecommunications, including mobile networks.