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Chapter 2: Basic Principles of HF Propagation

In this chapter, the basics of HF propagation are discussed to provide a foundation for understanding how radio waves travel over long distances using the ionosphere. Here are some key points covered in this chapter:

Overview of HF Radio Waves:

  • Frequency Range: HF radio waves fall within the frequency range of 3 to 30 MHz.
  • Skywave Propagation: HF waves can be refracted by the ionosphere, allowing them to “bounce” back to Earth, enabling long-distance communication. This is known as skywave propagation.
  • Groundwave Propagation: HF waves can also travel along the Earth’s surface for shorter distances. This is known as groundwave propagation.
  • Ionospheric Layers: The ionosphere, an electrically charged layer of the Earth’s atmosphere, plays a crucial role in HF propagation. It consists of several layers that vary in density and altitude, affecting how radio waves are refracted.
  • Critical Frequency: The critical frequency is the maximum frequency that can be used for skywave propagation at a specific angle of incidence.
  • Maximum Usable Frequency (MUF): The highest frequency that can be used for skywave propagation between two points on Earth at a specific time.
  • Skip Distance: The skip distance is the shortest distance between a transmitter and the point where the skywave is first returned to Earth.

Frequency Range: HF radio waves fall within the frequency range of 3 to 30 MHz.