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E3A05

RADIO WAVE PROPAGATION · Electromagnetic Waves and Specialized Propagation: Earth-Moon-Earth (EME) communications; meteor scatter; microwave tropospheric and scatter propagation; auroral propagation; daily variation of ionospheric propagation; circular polarization

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How are the component fields of an electromagnetic wave oriented?

  1. AThey are parallel
  2. BThey are tangential
  3. CThey are at right angles
  4. DThey are 90 degrees out of phase
Why In a radio wave traveling through free space, the electric field and the magnetic field are perpendicular to each other, and both are perpendicular to the direction the wave is traveling. That is why it is called a transverse electromagnetic (TEM) wave. Each field regenerates the other as the wave propagates, and their mutual right-angle geometry is what sets the direction of travel (the Poynting vector, E cross H).
Watch out The choice about being 90 degrees out of phase confuses space with time: in a plane wave in free space the E and H fields peak at the same instant, in phase, while it is their orientation in space that is 90 degrees apart.
E and H: right angles in space, in step in time.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E3A

  1. E3A01 What is the approximate maximum separation measured along the surface of the Earth between two stations commu…
  2. E3A02 What characterizes libration fading of an EME signal?
  3. E3A03 When scheduling EME contacts, which of these conditions will generally result in the least path loss?
  4. E3A04 In what direction does an electromagnetic wave travel?
  5. E3A05 How are the component fields of an electromagnetic wave oriented?
  6. E3A06 What should be done to continue a long-distance contact when the MUF for that path decreases due to darkness?
  7. E3A07 Atmospheric ducts capable of propagating microwave signals often form over what geographic feature?
  8. E3A08 When a meteor strikes the Earth's atmosphere, a linear ionized region is formed at what region of the ionosph…
  9. E3A09 Which of the following frequency ranges is most suited for meteor-scatter communications?
  10. E3A10 What determines the speed of electromagnetic waves through a medium?
  11. E3A11 What is a typical range for tropospheric duct propagation of microwave signals?
  12. E3A12 What is most likely to result in auroral propagation?
  13. E3A13 Which of these emission modes is best for auroral propagation?
  14. E3A14 What are circularly polarized electromagnetic waves?
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