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E3B06

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

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On which of the following amateur bands is long-path propagation most frequent?

  1. A160 meters and 80 meters
  2. B40 meters and 20 meters
  3. C10 meters and 6 meters
  4. D6 meters and 2 meters
Why Long-path signals take the longer great-circle route around the Earth, often 25,000 miles or more, so the band has to support many low-loss hops (or chordal hops) along a path where much of the ionosphere is in darkness. The 20 meter band is the classic long-path band, especially near sunrise and sunset along the grey line, with 40 meters working at night when absorption drops. These bands sit in the sweet spot: high enough to escape heavy D-layer absorption, low enough that the MUF supports the whole path.
Watch out 160 and 80 meters suffer too much absorption and noise to survive a trip most of the way around the world, and 10 and 6 meters would require a very high MUF sustained over the entire enormous path, which is rare.
Long path lives on 20 (with 40 at night); think grey-line DX on 14 MHz.
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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