What causes HF propagation?

High Frequency (HF) propagation refers to the way radio waves travel through the atmosphere, allowing long-distance communication over the horizon. Several factors affect such propagation:

1. Solar activity: The sun emits a range of electromagnetic radiation, including ultraviolet, X-rays, and charged particles. The EUV radiation ionizes the ionosphere, a region of the Earth's atmosphere, affecting its density and height.
2. The ionosphere: Radio waves can travel great distances by bouncing off the charged particles in the ionosphere. The height and density of free electrons have an impact on how radio waves travel.
3. Time of day: The sun ionizes the ionosphere during the day, allowing communication over longer distances at higher frequencies. At night, the ionization level drops, enabling communication at lower frequencies.
4. Space Weather conditions: Space Weather events, such as gemagnetic storms, can affect the ionosphere, causing disruptions to radio wave propagation.

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