SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-d-region-closest

Which ionospheric region is closest to the Earth's surface?

The D region.

Start playing free

  1. The D region ✔
  2. The E region
  3. The F1 region

Why: The D region is the lowest layer of the ionosphere. It forms in daylight and absorbs lower HF signals before they can reach the higher layers.

Huh, didn't know that: The D region is the most absorbent region for signals below 10 MHz in daylight.

The dad joke
You know you're a ham when you use your fishing rods as 20 meter verticals on camping trips.
Like this card?
Play the game

References

Answer: The D region. The D region is the lowest layer of the ionosphere. It forms in daylight and absorbs lower HF signals before they can reach the higher layers.

  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
    The D region
    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
    Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Ham RadioHow far can one hop via the F2 region normally travel?Ham RadioWhy is long-distance work on 160, 80, 60 and 40 meters harder in the daytime?Ham RadioHow far can one hop via the E region normally travel?

That's stuff everyone should know.