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E3B05

RADIO WAVE PROPAGATION · Transequatorial propagation; long-path propagation; ordinary and extraordinary waves; chordal hop; sporadic-E mechanisms; ground-wave propagation

E3B05E3B →

Which of the following paths is most likely to support long-distance propagation on 160 meters?

  1. AA path entirely in sunlight
  2. BPaths at high latitudes
  3. CA direct north-south path
  4. DA path entirely in darkness
Why On 160 meters the D layer is the limiting factor: daytime ionization absorbs low-frequency signals before they can reach the F layer and return. Absorption falls roughly as the inverse square of frequency, so at 1.8 MHz even modest D-layer ionization kills the path. Only when the entire path lies in darkness does the D layer recombine enough to let the signal make it to the F layer and back, which is why topband DX is worked in the middle of the night, ideally around gray line.
Watch out A sunlit path is exactly the worst case, since the D layer is fully ionized. High-latitude paths add auroral absorption and flutter, and a north-south path matters for transequatorial propagation on VHF, not for 160 meter absorption.
Topband loves the dark: 160 m DX needs the whole path in night, no D layer, no absorption.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E3B

  1. E3B01 Where is transequatorial propagation (TEP) most likely to occur?
  2. E3B02 What is the approximate maximum range for signals using transequatorial propagation?
  3. E3B03 At what time of day is transequatorial propagation most likely to occur?
  4. E3B04 What are "extraordinary" and "ordinary" waves?
  5. E3B05 Which of the following paths is most likely to support long-distance propagation on 160 meters?
  6. E3B06 On which of the following amateur bands is long-path propagation most frequent?
  7. E3B07 What effect does lowering a signal's transmitted elevation angle have on ionospheric HF skip propagation?
  8. E3B08 How does the maximum range of ground-wave propagation change when the signal frequency is increased?
  9. E3B09 At what time of year is sporadic-E propagation most likely to occur?
  10. E3B10 What is the effect of chordal-hop propagation?
  11. E3B11 At what time of day is sporadic-E propagation most likely to occur?
  12. E3B12 What is chordal-hop propagation?
  13. E3B13 What type of polarization is supported by ground-wave propagation?
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