Radio Wave Propagation
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1. What is a movement through a medium?
2. What is defined as a disturbance in a medium?
3. What type of waves has an up and down motion and travels at right angles to direction of propagation?
3. Transverse Waves.
4. What waves are also known as "compression waves" and travel in the same direction as the wave motion?
4. Longitudinal Waves or Sound Waves.
5. The vehicle through which the wave travels from one point to the next (Air, Space, Water, Wire) is known as what?
6. The Basic Antenna consists of what 4 areas?
6. Transmitter, Transmission Line, Antenna, Receiver.
7. Radio Waves travel at what speed?
7. Speed of Light.
8. What is the primary mechanism that enables long-distance (non-SATCOM) radio communications?
9. If signals arrive in phase, they will ___ and ______ the signal strength.
9. Add and Double.
10. Out of Phase will _______ and ______ signal strength.
10. Subtract and Reduce.
11. What occurs when a radio wave does not fade out completely when it reaches the radio horizon?
12. The atmosphere surrounding the earth is divided into what 4 layers?
12. Troposphere, Stratosphere, Ionosphere, Free Space.
13. What earth layer affects the variations of Weather and Temperature?
14. Which earth layer contains four layers of electrically charged ions and refracts radio waves back to earth?
15. What are the two principle RF transmitting methods?
15. Ground Waves and Sky Waves.
16. Ground waves are composed of what component waves?
16. Surface Wave, Space Wave, Ground Reflected Wave.
17. What occurs when radio signal can travel through many non-metallic objects and be picked up through the walls?
17. Line-of-Sight Propagation.
18. Which wave travels along the surface of the Earth and is attenuated by the Earth's voltage?
18. Surface Waves.
19. What wave is radiated upward and returned to Earth, is refracted in the ionosphere, and usually used in HF band?
19. Sky Waves.
20. The Ionosphere is ionized from what?
20. The sun.
21. The Ionosphere contains how many layers during the daytime?
21. D, E, F1, F2.
22. The Ionosphere contains how many layers during nightime?
22. D and F.
23. What are the three type of frequencies in the Ionosphere?
23. Critical, Above Critical, Below Critical.
24. What is the optimum frequency for desired refraction in the Ionosphere?
24. Critical Frequency.
25. What is a zone of silence between ground wave and sky wave?
26. Skip Zone.
26. What wave uses high take-off angle antennas and eliminates skip zones?
26. Near Vertical Incidence Sky Wave (NVIS).
27. Amount of refraction in the Ionosphere depends on what three areas?
27. Density, Frequency, and Angle.
28. What causes Wave Degradation?
- - Absorbtion
- - Fading
- - Multipath Fading - In/Out of Phase
- - Selective Fading
- - Transmission losses
- - Ground Reflection Loss
- - Free Space Loss
- - Electromagnetic Interference (EMI) for Natural and Man-made.
29. What is meant by Fading?
29. Variations in Signal Strength.
30. What is usually the major loss of energy due to?
30. Spreading as the signal travels.
31. What are some examples of Natural EMI?
31. Natural phenomena such as thunderstorms, snowstorms, cosmic sources, and the sun.
32. What are the four regular variations of the Ionosphere?
32. Daily, Seasonal, 11-year Sunspot Cycle, 27-day sun Spot Cycle.
33. What generates bursts of radiation that cause higher levels of ionization?
34. What are the three Irreglular Variations of the Ionosphere?
34. Sporadic E, Sudden Ionosphere Disturbances (SID), Ionosperic Storm.
35. What are the three types of frequency selection?
- - Maximum Usable Frequency
- - Lowest Usable Frequency
- - Optimum Usable Frequency
36. What weather considerations affect transmission?
- - Rain
- - Fog
- - Snow
- - Hail
- - Temperature inversion
37. When a radio wave gets trapped between a temperature inversion, it is known as what?
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