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SESK: Stuff Everyone Should Know · sesk.info/ham-knife-edge-diffraction

What effect may let radio signals travel beyond obstructions between two stations?

Knife-edge diffraction.

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  1. Knife-edge diffraction ✔
  2. Faraday rotation
  3. Doppler shift

Why: When a signal passes a sharp edge, like a ridge or a building top, some of it bends around and continues behind it. That is knife-edge diffraction.

Huh, didn't know that: This bending can let VHF signals reach places just behind a hill.

The dad joke
My signal went over the mountain with knife-edge diffraction. Very sharp move.
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References

Answer: Knife-edge diffraction. When a signal passes a sharp edge, like a ridge or a building top, some of it bends around and continues behind it. That is knife-edge diffraction.

  1. HamStudy 2026 Technician pool, T3C05 hamstudy.org/browse/E2_2026/T3C
    Knife-edge diffraction
    Checked 2026-10-09.

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