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E3B07

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

E3B07E3B →

What effect does lowering a signal's transmitted elevation angle have on ionospheric HF skip propagation?

  1. AFaraday rotation becomes stronger
  2. BThe MUF decreases
  3. CThe distance covered by each hop increases
  4. DThe critical frequency increases
Why Skip distance is set by geometry: the signal leaves the antenna, travels to the ionospheric layer at some height and returns. The shallower (lower) the takeoff angle, the farther downrange the wave travels before it reaches the reflecting layer and comes back, so each hop spans more ground. That is why DXers favor low takeoff angles, with single hops of 2000 miles or more possible off the F2 layer, while high angles give short hops or near-vertical local coverage.
Watch out The choice about MUF going down has it backwards: lowering the elevation angle makes the wave strike the layer more obliquely, which raises the maximum usable frequency for that path. Critical frequency is measured straight up at vertical incidence and does not depend on your antenna's takeoff angle at all.
Low angle, long hop. Flatter launch equals farther DX (and a higher MUF, not a lower one).
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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