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E3B08

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

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How does the maximum range of ground-wave propagation change when the signal frequency is increased?

  1. AIt stays the same
  2. BIt increases
  3. CIt decreases
  4. DIt peaks at roughly 8 MHz
Why Ground-wave (surface-wave) signals travel by hugging the Earth's surface, and the ground acts as a lossy dielectric that absorbs energy from the wave. That absorption grows rapidly as frequency rises, so the useful range shrinks: 160 and 80 meters can give hundreds of miles of ground wave over good soil, while at 10 meters ground wave is only good for a few miles. This is why AM broadcast and LF/MF services rely on ground wave for daytime coverage.
Watch out The idea that range increases with frequency confuses ground wave with skywave or line-of-sight VHF work; higher frequencies do not penetrate or follow the ground better, they are attenuated more. The 8 MHz peak choice is simply invented, there is no such peak.
Lower frequency, longer ground wave. Think of AM broadcast stations at 1 MHz covering whole states in daytime.
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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