Download
g3 radio wave propagation 3 exam questions 3 groups n.
Skip this Video
Loading SlideShow in 5 Seconds..
G3 - RADIO WAVE PROPAGATION [3 Exam Questions - 3 Groups] PowerPoint Presentation
Download Presentation
G3 - RADIO WAVE PROPAGATION [3 Exam Questions - 3 Groups]

G3 - RADIO WAVE PROPAGATION [3 Exam Questions - 3 Groups]

269 Views Download Presentation
Download Presentation

G3 - RADIO WAVE PROPAGATION [3 Exam Questions - 3 Groups]

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. G3 - RADIO WAVE PROPAGATION [3 Exam Questions - 3 Groups] • G3A Sunspots and solar radiation; ionospheric disturbances; propagation forecasting and indices • G3B Maximum Usable Frequency; Lowest Usable Frequency; propagation "hops" • G3C Ionospheric layers; critical angle and frequency; HF scatter; Near Vertical Incidence Sky waves Radio Wave Propagation

  2. Ionospheric Layers Radio Wave Propagation

  3. Some Characteristics of the Layers in the Ionosphere D Layer – 25-55 mi - Most Dense – Daytime Layer – ionized only while sunlit - Absorbs HF below 10 MHz E Layer – 55-90 mi – less dense – Daytime Layer – ionized while sunlit – F Layer (F1 and F2 in daytime – recombines at night) 90 -250 mi – not dense – Refracts HF Radio Wave Propagation

  4. G3C01 Which of the following ionospheric layers is closest to the surface of the Earth? • A. The D layer • B. The E layer • C. The F1 layer • D. The F2 layer Radio Wave Propagation

  5. G3C01 Which of the following ionospheric layers is closest to the surface of the Earth? • A. The D layer • B. The E layer • C. The F1 layer • D. The F2 layer Radio Wave Propagation

  6. G3C02 When can the F2 region be expected to reach its maximum height at your location? • A. At noon during the summer • B. At midnight during the summer • C. At dusk in the spring and fall • D. At noon during the winter Radio Wave Propagation

  7. G3C02 When can the F2 region be expected to reach its maximum height at your location? • A. At noon during the summer • B. At midnight during the summer • C. At dusk in the spring and fall • D. At noon during the winter Radio Wave Propagation

  8. Critical Angle Radio Wave Propagation

  9. G3C04 What does the term "critical angle" mean as used in radio wave propagation? • A. The long path azimuth of a distant station • B. The short path azimuth of a distant station • C. The lowest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions • D. The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions Radio Wave Propagation

  10. G3C04 What does the term "critical angle" mean as used in radio wave propagation? • A. The long path azimuth of a distant station • B. The short path azimuth of a distant station • C. The lowest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions • D. The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions Radio Wave Propagation

  11. G3C05 Why is long distance communication on the 40, 60, 80 and 160 meter bands more difficult during the day? • A. The F layer absorbs these frequencies during daylight hours • B. The F layer is unstable during daylight hours • C. The D layer absorbs these frequencies during daylight hours • D. The E layer is unstable during daylight hours Radio Wave Propagation

  12. G3C05 Why is long distance communication on the 40, 60, 80 and 160 meter bands more difficult during the day? • A. The F layer absorbs these frequencies during daylight hours • B. The F layer is unstable during daylight hours • C. The D layer absorbs these frequencies during daylight hours • D. The E layer is unstable during daylight hours Radio Wave Propagation

  13. G3C12 Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz? • A. The F2 layer • B. The F1 layer • C. The E layer • D. The D layer Radio Wave Propagation

  14. G3C12 Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz? • A. The F2 layer • B. The F1 layer • C. The E layer • D. The D layer Radio Wave Propagation

  15. Reflection vs Refraction Radio Wave Propagation

  16. Reflection Light reflects when it bounces off the surface of a material. It bounces away at the same angle that it hits the material. So if it hits at an angle of 25 degrees, it will bounce in the opposite direction at 25 degrees (the total angle being 50 degrees). Read more: http://atomic-molecular-optical-physics.suite101.com/article.cfm/reflection_vs_refraction#ixzz0Xz9aM4PZ Radio Wave Propagation

  17. Refraction Light refracts as it passes through a material. It's direction changes, but it still passes through. Light travels at a maximum speed -- the speed of light in a vacuum, but when traveling in anything else it slows down. Different materials slow the speed of passing light at different rates. This property of matter is called the refractive index. When refracting, light doesn't change it's frequency, but since it changes it's speed, it must also change it's wavelength (it gets squished or elongated). Frequency, wavelength, and speed are all related, so if one property changes, another must as well.Read more: http://atomic-molecular-optical-physics.suite101.com/article.cfm/reflection_vs_refraction#ixzz0Xz9pEASe Radio Wave Propagation

  18. Skywave Hop Distances Each reflection (refraction) from the ionosphere is called a hop and allow radio waves to be received hundreds or thousands of miles away. Signals received in this way are called skywave and propagation via the ionosphere is called skip. The higher the region from which the reflection takes place, the longer the hop. Signals reflected from the uppermost F2 layer can travel up to 2500 miles before returning to the ground. Hops that use the E layer are shorter, up to 1200 miles because of the lower reflecting height. Radio Wave Propagation

  19. Multi Hop Sky wave propagation can consist of multiple hops because the earth’s surface also reflects radio waves. Highly conductive salt water ocean is a particularly good reflector. Propagation between Europe and the US, for example, requires up to seven hops depending on location and time of day. Hops can also be considerably shorter than those maximum figures if the ionosphere is sufficiently ionized so that the critical angle is high. Signals received via sky way at much shorter than maximum hop distance are called short skip. Radio Wave Propagation

  20. G3B09 What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region? • A. 180 miles • B. 1,200 miles • C. 2,500 miles • D. 12,000 miles Radio Wave Propagation

  21. G3B09 What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region? • A. 180 miles • B. 1,200 miles • C. 2,500 miles • D. 12,000 miles Radio Wave Propagation

  22. G3B10 What is the maximum distance along the Earth's surface that is normally covered in one hop using the E region? • A. 180 miles • B. 1,200 miles • C. 2,500 miles • D. 12,000 miles Radio Wave Propagation

  23. G3B10 What is the maximum distance along the Earth's surface that is normally covered in one hop using the E region? • A. 180 miles • B. 1,200 miles • C. 2,500 miles • D. 12,000 miles Radio Wave Propagation

  24. G3B14 Which of the following is a good indicator of the possibility of sky-wave propagation on the 6 meter band? • A. Short hop sky-wave propagation on the 10 meter band • B. Long hop sky-wave propagation on the 10 meter band • C. Severe attenuation of signals on the 10 meter band • D. Long delayed echoes on the 10 meter band Radio Wave Propagation

  25. G3B14 Which of the following is a good indicator of the possibility of sky-wave propagation on the 6 meter band? • A. Short hop sky-wave propagation on the 10 meter band • B. Long hop sky-wave propagation on the 10 meter band • C. Severe attenuation of signals on the 10 meter band • D. Long delayed echoes on the 10 meter band Radio Wave Propagation

  26. G3C03 Why is the F2 region mainly responsible for the longest distance radio wave propagation? • A. Because it is the densest ionospheric layer • B. Because it does not absorb radio waves as much as other ionospheric regions • C. Because it is the highest ionospheric region • D. All of these choices are correct Radio Wave Propagation

  27. G3C03 Why is the F2 region mainly responsible for the longest distance radio wave propagation? • A. Because it is the densest ionospheric layer • B. Because it does not absorb radio waves as much as other ionospheric regions • C. Because it is the highest ionospheric region • D. All of these choices are correct Radio Wave Propagation

  28. Directional Antenna Radio Wave Propagation

  29. Long and Short Path Radio Wave Propagation

  30. G2D06 How is a directional antenna pointed when making a "long-path" contact with another station? • A. Toward the rising sun • B. Along the Gray Line • C. 180 degrees from its short-path heading • D. Toward the North Operating Procedures

  31. G2D06 How is a directional antenna pointed when making a "long-path" contact with another station? • A. Toward the rising sun • B. Along the Gray Line • C. 180 degrees from its short-path heading • D. Toward the North Operating Procedures

  32. G3B13 How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation? • A. Periodic fading approximately every 10 seconds • B. Signal strength increased by 3 dB • C. The signal will be cancelled causing severe attenuation • D. A well-defined echo can be heard Radio Wave Propagation

  33. G3B13 How might a sky-wave signal sound if it arrives at your receiver by both short path and long path propagation? • A. Periodic fading approximately every 10 seconds • B. Signal strength increased by 3 dB • C. The signal will be cancelled causing severe attenuation • D. A well-defined echo can be heard Radio Wave Propagation

  34. Sunspots • Sunspot number refers to the number of sunspots and groups • Sunspots ‘appear’ to move due to the 28 day rotation of the sun. • Solar Flux Index (SFI) Describes the amount of 2800MHz (10.7cm) radio energy coming from the sun. SFI starts at minimum of 65 with no maximum. • K index – K values of 0 to 9 represents short term stability of earth’s geo-magnetic field. Updated ever 3 hours by NIST. • The higher the sunspot count, the more ionization • Thus, higher sunspot counts support a higher Maximum Usable Frequency (MUF) Radio Wave Propagation

  35. Sunspot Cycle • Sunspots peak during 11-year cycles Radio Wave Propagation

  36. Reconstruction of 11,000 year Radio Wave Propagation

  37. Sunspot Forecast PEAK Radio Wave Propagation

  38. G3A09 What is the effect on radio communications when sunspot numbers are high? • A. High-frequency radio signals become weak and distorted • B. Frequencies above 300 MHz become usable for long-distance communication • C. Long-distance communication in the upper HF and lower VHF range is enhanced • D. Long-distance communication in the upper HF and lower VHF range is diminished Radio Wave Propagation

  39. G3A09 What is the effect on radio communications when sunspot numbers are high? • A. High-frequency radio signals become weak and distorted • B. Frequencies above 300 MHz become usable for long-distance communication • C. Long-distance communication in the upper HF and lower VHF range is enhanced • D. Long-distance communication in the upper HF and lower VHF range is diminished Radio Wave Propagation

  40. G3A10 What is the sunspot number? • A. A measure of solar activity based on counting sunspots and sunspot groups • B. A 3 digit identifier which is used to track individual sunspots • C. A measure of the radio flux from the sun measured at 10.7 cm • D. A measure of the sunspot count based on radio flux measurements Radio Wave Propagation

  41. G3A10 What is the sunspot number? • A. A measure of solar activity based on counting sunspots and sunspot groups • B. A 3 digit identifier which is used to track individual sunspots • C. A measure of the radio flux from the sun measured at 10.7 cm • D. A measure of the sunspot count based on radio flux measurements Radio Wave Propagation

  42. G3A11 How long is the typical sunspot cycle? • A. Approximately 8 minutes • B. Between 20 and 40 hours • C. Approximately 28 days • D. Approximately 11 years Radio Wave Propagation

  43. G3A11 How long is the typical sunspot cycle? • A. Approximately 8 minutes • B. Between 20 and 40 hours • C. Approximately 28 days • D. Approximately 11 years Radio Wave Propagation

  44. Ionospheric Layers Radio Wave Propagation

  45. Daytime Nighttime HF Propagation Radio Wave Propagation

  46. G3A17 At what point in the solar cycle does the 20 meter band usually support worldwide propagation during daylight hours? • A. At the summer solstice • B. Only at the maximum point of the solar cycle • C. Only at the minimum point of the solar cycle • D. At any point in the solar cycle Radio Wave Propagation

  47. G3A17 At what point in the solar cycle does the 20 meter band usually support worldwide propagation during daylight hours? • A. At the summer solstice • B. Only at the maximum point of the solar cycle • C. Only at the minimum point of the solar cycle • D. At any point in the solar cycle Radio Wave Propagation

  48. G3A18 If the HF radio-wave propagation (skip) is generally good on the 24-MHz and 28-MHz bands for several days, when might you expect a similar condition to occur? • A. 7 days later • B. 14 days later • C. 28 days later • D. 90 days later Radio Wave Propagation

  49. G3A18 If the HF radio-wave propagation (skip) is generally good on the 24-MHz and 28-MHz bands for several days, when might you expect a similar condition to occur? • A. 7 days later • B. 14 days later • C. 28 days later • D. 90 days later Radio Wave Propagation

  50. G3A19 Which frequencies are least reliable for long distance communications during periods of low solar activity? • A. Frequencies below 3.5 MHz • B. Frequencies near 3.5 MHz • C. Frequencies at or above 10 MHz • D. Frequencies above 20 MHz Radio Wave Propagation