SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-nvis

What is NVIS propagation?

Short distance MF or HF at high elevation angles.

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  1. Double hop propagation near the LUF
  2. Long path HF at sunrise and sunset
  3. Short distance MF or HF at high elevation angles ✔

Why: Near vertical incidence skywave sends signals nearly straight up so they come back down close by. It is useful for regional contacts, such as inside a state.

Huh, didn't know that: The highest frequency refracted back to Earth at a given angle is called the critical frequency.

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References

Answer: Short distance MF or HF at high elevation angles. Near vertical incidence skywave sends signals nearly straight up so they come back down close by. It is useful for regional contacts, such as inside a state.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    Short distance MF or HF propagation at high elevation angles
    Checked 2026-10-10.
  2. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    The highest frequency which is refracted back to Earth
    Checked 2026-10-10.

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