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SESK: Stuff Everyone Should Know · sesk.info/ham-radio-horizon

Why is the VHF and UHF radio horizon farther than the visual horizon?

The atmosphere refracts radio waves slightly.

  1. Radio waves move faster than light
  2. The atmosphere bends radio waves slightly ✔
  3. Radio waves are not blocked by dust

Why: The atmosphere bends radio waves a little, so they follow Earth's curve a bit farther than light does. That stretches the radio horizon past what you can see.

Huh, didn't know that: UHF signals are rarely heard past the radio horizon because the ionosphere usually does not carry them.

The dad joke
Why did the radio wave bend? It wanted to see over the horizon.
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Sources

  1. NCVEC 2026-2030 Technician Question Pool (Element 2), errata Feb 19, 2026 https://www.ncvec.org/downloads/2026-2030%20Technician%20Pool%20and%20Syllabus%20Public%20Release%20Feb%2019%202026.pdf

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