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General License Course Chapter 8

General License Course Chapter 8. Lesson Plan Module 35 – The Sun. The Sun. Sunspots or Solar Cycle – approximately an 11-year cycle Sunspot number represents the number of sunspots and groups present at a given time Sunspot numbers are useful in assessing the overall solar activity

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General License Course Chapter 8

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  1. General License CourseChapter 8 Lesson Plan Module 35 – The Sun

  2. The Sun • Sunspots or Solar Cycle – approximately an 11-year cycle • Sunspot number represents the number of sunspots and groups present at a given time • Sunspot numbers are useful in assessing the overall solar activity • The more sunspots, the more UV is generated, creating more ionization and improving propagation conditions on the HF bands and possibly into the lower VHF range 2015 General License Course

  3. Solar Activity • High sunspot numbers mean poor conditions on 80 & 40 meters (increased absorption) • Low sunspot numbers means 15, 12, & 10 meter bands are closed (no sky-wave) • 20 meter band is usually good regardless of sunspot number during the daytime • Sun rotates every 28 days causing sunspots to reappear if still present and HF propagation tends to repeat, as well 2015 General License Course

  4. Measuring Solar Activity 2015 General License Course

  5. Measuring Solar Activity • Solar-Flux Index (SFI) –amount of 2800 MHz (10.7 cm wavelength) energy from the Sun • K index (0-9) – the short term stability of the Earth’s magnetic or geomagneticfield • 0 is quiet, 9 is extreme storm • A index (0-400) – long-term geomagnetic field stability around the world • Values 0 (stable) to 400 (greatly disturbed) 2015 General License Course

  6. Assessing Propagation • MUF – Maximum Usable Frequency • Highest frequency for propagation between two points (higher than MUF will not be refracted enough to get back to Earth) • LUF – Lowest Usable Frequency • Lowest frequency for propagation between two points (lower than LUF will be absorbed) • MUF/LUF vary with the time, season, amount of solar radiation and geomagnetic stability 2015 General License Course

  7. Assessing Propagation • MUF drops below LUF, no ordinary sky-wave propagation between those two points • Check actual band conditions between two points by listening for beacon stations • The NCDXF supports an international network of beacon stations that transmit continuously on 20-10 meters 2015 General License Course

  8. Solar Disturbances • Solar flare – a large eruption of energy and solar material on the surface of the Sun • Coronal hole – a weak area in the Sun’s outer layer where ionized gas and charged particles escape the Sun’s magnetic field • Coronal mass ejection (CME) – an ejection of large amounts of material from the corona • CME may be directed in a narrow stream or wide spray (disruptive to radio communications) 2015 General License Course

  9. Solar Disturbances • UV & X-ray radiation from solar flares travels at the speed of light and reaches the Earth’s ionosphere in about 8 minutes • Increases D layer ionization and absorption dramatically, causing a radio blackout (Sudden Ionospheric Disturbance or SID) that can last from seconds to several hours • Affects lower bands more than higher bands • SID only impacts the sunny side of the Earth so dark side may be relatively unaffected 2015 General License Course

  10. Solar Disturbances • Geomagnetic Disturbances • Sun gives off a stream of particles called solar wind • Charged particles from coronal holes and CMEs take up to 20 to 40 hours to reach the Earth • Particles increase ionization in the E region • Causes auroral displays and geomagnetic storms 2015 General License Course

  11. Solar Disturbances • Sudden change in geomagnetic field disrupts the upper ionosphere, causing long-distance paths at high latitudes near the magnetic poles to be wiped out for a period of hours to days • Auroras are actually a glow of gases ionized by the incoming charged particles as they flow vertically down into the atmosphere, guided by the magnetic field • Auroral propagation is strongest on 6 and 2 meters (hiss or buzz) 2015 General License Course

  12. Practice Questions 2015 General License Course

  13. What is the significance of the sunspot number with regard to HF propagation? A. Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies B. Lower sunspot numbers generally indicate greater probability of sporadic E propagation C. A zero sunspot number indicate radio propagation is not possible on any band D. All of these choices are correct G3A01 2015 General License Course

  14. What is the significance of the sunspot number with regard to HF propagation? A. Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies B. Lower sunspot numbers generally indicate greater probability of sporadic E propagation C. A zero sunspot number indicate radio propagation is not possible on any band D. All of these choices are correct G3A01 2015 General License Course

  15. What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves? A. It enhances propagation on all HF frequencies B. It disrupts signals on lower frequencies more than those on higher frequencies C. It disrupts communications via satellite more than direct communications D. None, because only areas on the night side of the Earth are affected G3A02 2015 General License Course

  16. What effect does a Sudden Ionospheric Disturbance have on the daytime ionospheric propagation of HF radio waves? A. It enhances propagation on all HF frequencies B. It disrupts signals on lower frequencies more than those on higher frequencies C. It disrupts communications via satellite more than direct communications D. None, because only areas on the night side of the Earth are affected G3A02 2015 General License Course

  17. Approximately how long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio propagation on the Earth? A. 28 days B. 1 to 2 hours C. 8 minutes D. 20 to 40 hours G3A03 2015 General License Course

  18. Approximately how long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio propagation on the Earth? A. 28 days B. 1 to 2 hours C. 8 minutes D. 20 to 40 hours G3A03 2015 General License Course

  19. Which of the following are least reliable for long distance communications during periods of low solar activity? A. 80 meters and 160 meters B. 60 meters and 40 meters C. 30 meters and 20 meters D. 15 meters, 12 meters and 10 meters G3A04 2015 General License Course

  20. Which of the following are least reliable for long distance communications during periods of low solar activity? A. 80 meters and 160 meters B. 60 meters and 40 meters C. 30 meters and 20 meters D. 15 meters, 12 meters and 10 meters G3A04 2015 General License Course

  21. What is the solar flux index? A. A measure of the highest frequency that is useful for ionospheric propagation between two points on the Earth B. A count of sunspots which is adjusted for solar emissions C. Another name for the American sunspot number D. A measure of solar radiation at 10.7 centimeters wavelength G3A05 2015 General License Course

  22. What is the solar flux index? A. A measure of the highest frequency that is useful for ionospheric propagation between two points on the Earth B. A count of sunspots which is adjusted for solar emissions C. Another name for the American sunspot number D. A measure of solar radiation at 10.7 centimeters wavelength G3A05 2015 General License Course

  23. What is a geomagnetic storm? A. A sudden drop in the solar flux index B. A thunderstorm which affects radio propagation C. Ripples in the ionosphere D. A temporary disturbance in the Earth's magnetosphere G3A06 2015 General License Course

  24. What is a geomagnetic storm? A. A sudden drop in the solar flux index B. A thunderstorm which affects radio propagation C. Ripples in the ionosphere D. A temporary disturbance in the Earth's magnetosphere G3A06 2015 General License Course

  25. 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 G3A07 2015 General License Course

  26. 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 G3A07 2015 General License Course

  27. Which of the following effects can a geomagnetic storm have on radio propagation? A. Improved high-latitude HF propagation B. Degraded high-latitude HF propagation C. Improved ground-wave propagation D. Improved chances of UHF ducting G3A08 2015 General License Course

  28. Which of the following effects can a geomagnetic storm have on radio propagation? A. Improved high-latitude HF propagation B. Degraded high-latitude HF propagation C. Improved ground-wave propagation D. Improved chances of UHF ducting G3A08 2015 General License Course

  29. What effect does a high sunspot number have on radio communications? 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. Microwave communications become unstable G3A09 2015 General License Course

  30. What effect does a high sunspot number have on radio communications? 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. Microwave communications become unstable G3A09 2015 General License Course

  31. What causes HF propagation conditions to vary periodically in a 28 day cycle? A. Long term oscillations in the upper atmosphere B. Cyclic variation in the Earth’s radiation belts C. The Sun’s rotation on its axis D. The position of the Moon in its orbit G3A10 2015 General License Course

  32. What causes HF propagation conditions to vary periodically in a 28 day cycle? A. Long term oscillations in the upper atmosphere B. Cyclic variation in the Earth’s radiation belts C. The Sun’s rotation on its axis D. The position of the Moon in its orbit G3A10 2015 General License Course

  33. Approximately how long is the typical sunspot cycle? A. 8 minutes B. 40 hours C. 28 days D. 11 years G3A11 2015 General License Course

  34. Approximately how long is the typical sunspot cycle? A. 8 minutes B. 40 hours C. 28 days D. 11 years G3A11 2015 General License Course

  35. What does the K-index indicate? A. The relative position of sunspots on the surface of the Sun B. The short term stability of the Earth’s magnetic field C. The stability of the Sun’s magnetic field D. The solar radio flux at Boulder, Colorado G3A12 2015 General License Course

  36. What does the K-index indicate? A. The relative position of sunspots on the surface of the Sun B. The short term stability of the Earth’s magnetic field C. The stability of the Sun’s magnetic field D. The solar radio flux at Boulder, Colorado G3A12 2015 General License Course

  37. What does the A-index indicate? A. The relative position of sunspots on the surface of the Sun B. The amount of polarization of the Sun's electric field C. The long term stability of the Earth’s geomagnetic field D. The solar radio flux at Boulder, Colorado G3A13 2015 General License Course

  38. What does the A-index indicate? A. The relative position of sunspots on the surface of the Sun B. The amount of polarization of the Sun's electric field C. The long term stability of the Earth’s geomagnetic field D. The solar radio flux at Boulder, Colorado G3A13 2015 General License Course

  39. How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes? A. HF communications are improved B. HF communications are disturbed C. VHF/UHF ducting is improved D. VHF/UHF ducting is disturbed G3A14 2015 General License Course

  40. How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes? A. HF communications are improved B. HF communications are disturbed C. VHF/UHF ducting is improved D. VHF/UHF ducting is disturbed G3A14 2015 General License Course

  41. How long does it take charged particles from coronal mass ejections to affect radio propagation on the Earth? A. 28 days B. 14 days C. 4 to 8 minutes D. 20 to 40 hours G3A15 2015 General License Course

  42. How long does it take charged particles from coronal mass ejections to affect radio propagation on the Earth? A. 28 days B. 14 days C. 4 to 8 minutes D. 20 to 40 hours G3A15 2015 General License Course

  43. What is a possible benefit to radio communications resulting from periods of high geomagnetic activity? A. Auroras that can reflect VHF signals B. Higher signal strength for HF signals passing through the polar regions C. Improved HF long path propagation D. Reduced long delayed echoes G3A16 2015 General License Course

  44. What is a possible benefit to radio communications resulting from periods of high geomagnetic activity? A. Auroras that can reflect VHF signals B. Higher signal strength for HF signals passing through the polar regions C. Improved HF long path propagation D. Reduced long delayed echoes G3A16 2015 General License Course

  45. Which of the following applies when selecting a frequency for lowest attenuation when transmitting on HF? A. Select a frequency just below the MUF B. Select a frequency just above the LUF C. Select a frequency just below the critical frequency D. Select a frequency just above the critical frequency G3B03 2015 General License Course

  46. Which of the following applies when selecting a frequency for lowest attenuation when transmitting on HF? A. Select a frequency just below the MUF B. Select a frequency just above the LUF C. Select a frequency just below the critical frequency D. Select a frequency just above the critical frequency G3B03 2015 General License Course

  47. What is a reliable way to determine if the MUF is high enough to support skip propagation between your station and a distant location on frequencies between 14 and 30 MHz? A. Listen for signals from an international beacon in the frequency range you plan to use B. Send a series of dots on the band and listen for echoes from your signal C. Check the strength of TV signals from Western Europe D. Check the strength of signals in the MF AM broadcast band G3B04 2015 General License Course

  48. What is a reliable way to determine if the MUF is high enough to support skip propagation between your station and a distant location on frequencies between 14 and 30 MHz? A. Listen for signals from an international beacon in the frequency range you plan to use B. Send a series of dots on the band and listen for echoes from your signal C. Check the strength of TV signals from Western Europe D. Check the strength of signals in the MF AM broadcast band G3B04 2015 General License Course

  49. What usually happens to radio waves with frequencies below the LUF? A. They are bent back to the Earth B. They pass through the ionosphere C. They are completely absorbed by the ionosphere D. They are bent and trapped in the ionosphere to circle the Earth G3B06 2015 General License Course

  50. What usually happens to radio waves with frequencies below the LUF? A. They are bent back to the Earth B. They pass through the ionosphere C. They are completely absorbed by the ionosphere D. They are bent and trapped in the ionosphere to circle the Earth G3B06 2015 General License Course

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