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G3C03

RADIO WAVE PROPAGATION · - Ionospheric regions; critical angle and frequency; HF scatter; near vertical incidence skywave (NVIS)

G3C03G3C →

Why is skip propagation via the F2 region longer than that via the other ionospheric regions?

  1. ABecause it is the densest
  2. BBecause of the Doppler effect
  3. CBecause it is the highest
  4. DBecause of temperature inversions
Why Single-hop distance is set by geometry: the higher the reflecting layer, the shallower the angle at which a ray can still be bent back and the farther it lands. The F2 region sits roughly 250 to 400 km up, well above the E region near 100 km, so one F2 hop can span about 2500 miles while an E-region hop is limited to roughly 1200 miles.
Watch out F2 is indeed the most heavily ionized region, but that high electron density is what raises the MUF, not what stretches the hop; the extra distance comes purely from the layer's altitude.
Highest mirror, longest bounce: F2 at ~250+ km gives ~2500 miles per hop, E at ~100 km only ~1200.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of G3C

  1. G3C01 Which ionospheric region is closest to the surface of Earth?
  2. G3C02 What is meant by the term "critical frequency" at a given incidence angle?
  3. G3C03 Why is skip propagation via the F2 region longer than that via the other ionospheric regions?
  4. G3C04 What does the term "critical angle" mean, as applied to radio wave propagation?
  5. G3C05 Why is long-distance communication on the 40-, 60-, 80-, and 160-meter bands more difficult during the day?
  6. G3C06 What is a characteristic of HF scatter?
  7. G3C07 What makes HF scatter signals often sound distorted?
  8. G3C08 Why are HF scatter signals in the skip zone usually weak?
  9. G3C09 What type of propagation allows signals to be heard in the transmitting station's skip zone?
  10. G3C10 What is near vertical incidence skywave (NVIS) propagation?
  11. G3C11 Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?
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