General Licensing Class “G3”

1. General Licensing Class“G3” Presented by the Acadiana Amateur Radio Assoc. Lafayette, Louisiana

2. General Class Element 3 Course Presentation • ELEMENT 3 SUB-ELEMENTS G1 – Commission’s Rules G2 – Operating Procedures G3 – Radio Wave Propagation G4 – Amateur Radio Practices G5 – Electrical Principles G6 – Circuit Components G7 – Practical Circuits G8 – Signals and Emissions G9 – Antennas G0 – Electrical and RF Safety

3. G3 … Radio Wave PropagationG3A • Sunspots and solar radiation • It takes approximately 8 minutes for increased ultraviolet and X-ray radiation from solar flares to affect radio-wave propagation on the Earth. (Solar winds coming towards the earth from the sun)

4. G3 … Radio Wave PropagationG3A • Sunspots and solar radiation(cont) • The typical sunspot cycle is approximately 11 years long

5. G3 … Radio Wave Propagation G3A • Sunspots and solar radiation(cont) • The sunspot number is a measure of solar activity based on counting sunspots and sunspot groups August 2008 September 1991

6. G3 … Radio Wave Propagation G3A • Sunspots and solar radiation(cont) • 2008 is hopefully the end of Solar Cycle 23 and the beginning of Solar Cycle 24.

7. G3 … Radio Wave PropagationG3A • Ionospheric disturbances • Geomagnetic disturbance is a significant change in the Earth's magnetic field over a short period. • A Sudden Ionospheric Disturbance (SID) disrupts signals on lower frequencies more than those on higher frequencies affecting the daytime ionospheric propagation of HF radio waves • An amateur station can try a higher frequency to continue communications during a sudden ionospheric disturbance.

8. Layers of the Atmosphere

9. Atmospheric Layers Terms we’ve heard before from space shuttle launches. Now apply them to Ham Radio Ionosphere 31 – 400 miles Stratosphere 6 – 31 miles Troposphere 0 – 6 miles

10. Atmospheric Layers(cont) • Troposphere • Closest to Earth • Max ~ 16 miles • Ionosphere • 4 layers: D; E; F1; F2 • Responsible for most long range communications • Ultraviolet radiation causes most ionization • Ionization max at midday, min at sunrise

11. Ultraviolet and other radiation from the sun Strikes atoms in the upper atmosphere Releasing an electron forming positive & negative ions - Electron (Negative Ion) + Positive Ion Electrically Neutral Atom How the Ionosphere is Formed Ultraviolet radiation is most responsible for ionization in the outer atmosphere.

12. Layers of the Ionosphere G3A • Lowest part: D layer has enough collisions to cause it to disappear after sunset • Remaining ions and electrons recombine, without sunlight new ones are no longer produced • Layer return at sunrise

13. At night.... Regions in the IonosphereG3A During the day.... • The “D” Region is closest to Earth • The “D” Region absorbs MF/HF radio signals • The “F2” Region is most responsible for long distance communication • The “D” & “E” Regions disappear • The “F1” & “F2” Regions combine into one with reduced ionization

14. G3 … Radio Wave PropagationG3A • Ionospheric disturbances (cont) • Latitudes, greater than 45 degrees North or South latitude, have propagation paths that are more sensitive to geomagnetic disturbances • An effect of a geomagnetic storm on radio-wave propagation can be degraded high-latitude HF propagation. • HF radio communications are disturbed by the charged particles that reach the Earth from solar coronal holes. • It takes charged particles from Coronal Mass Ejections about 20 to 40 hours to affect radio-wave propagation on the Earth

15. G3 … Radio Wave PropagationG3A • Propagation forecasting and indices • The solar flux index is a measure of the radio energy emitted by the sun. • The solar-flux index is a measure of solar activity at 10.7 cm. • Long-distance communication in the upper HF and lower VHF range has enhanced radio communications when sunspot numbers are high.

16. G3 … Radio Wave PropagationG3A • Propagation forecasting and indices (cont) • The K-index is a measure of the short-term stability of the Earth’s magnetic field. • The A-index is an indicator of the long-term stability of the Earth’s geomagnetic field. • At any point in the solar cycle, the 20-meter band usually supports worldwide propagation during daylight hours. • If the HF radio-wave propagation (skip) is generally good on the 24-MHz and 28-MHz bands for several days, you might expect a similar condition to occur 28 days later.

17. G3 … Radio Wave PropagationG3A • Propagation forecasting and indices (cont)

18. G3 … Radio Wave PropagationG3A • Propagation forecasting and indices(cont) • Frequencies above 20 MHz are the least reliable for long distance communications during periods of low solar activity. • A possible benefit to radio communications resulting from periods of high geomagnetic activity is Aurora that can reflect VHF signals. Aurora Borealis

19. G3 … Radio Wave PropagationG3B • Maximum Usable Frequency • MUF stands for the Maximum Usable Frequency for communications between two points • The 15-meter band should offer the best chance for a successful contact if the maximum usable frequency (MUF) between the two stations is 22 MHz. • The 20-meter band should offer the best chance for a successful contact if the maximum usable frequency (MUF) between the two stations is 16 MHz.

20. G3 … Radio Wave PropagationG3B • Critical & Maximum Usable Frequency • The frequency at which a signal sent vertically will pass right through the ionosphere is called the critical frequency. • The frequency at which communication just starts to fail is known as the Maximum Usable Frequency (MUF). It is generally three to five times the critical frequency, dependent upon the layer being used and the angle of incidence.

21. G3 … Radio Wave PropagationG3B • Maximum Usable Frequency(cont) • For lowest attenuation when transmitting on HF, select a frequency just below the MUF. • A reliable way to determine if the maximum usable frequency (MUF) is high enough to support 28-MHz propagation between your station and Western Europe is to listen for signals on a 28 MHz international beacon. • Radio waves with frequencies below the maximum usable frequency (MUF) are usually bent back to the Earth after they are sent into the ionosphere.

22. G3 … Radio Wave PropagationG3B • Maximum Usable Frequency(cont) • The factors that affect the maximum usable frequency (MUF) are: • Path distance and location • Time of day and season • Solar radiation and ionospheric disturbance [All of these choices are correct] • Lowest Usable Frequency • LUF stands for the Lowest Usable Frequency for communications between two points. • Radio waves with frequencies below the lowest usable frequency (LUF) are usually completely absorbed by the ionosphere

23. G3 … Radio Wave PropagationG3B • Propagation “hops” • The maximum distance along the Earth's surface that is normally covered in one hop using the F2 region is 2,500 miles. • The maximum distance along the Earth's surface that is normally covered in one hop using the E region is 1,200 miles.

24. G3 … Radio Wave PropagationG3B • Propagation “hops” (cont) • When the lowest usable frequency (LUF) exceeds the maximum usable frequency (MUF), no HF radio frequency will support communications over the path. • A sky-wave signal will sound like a well-defined echo when it arrives at your receiver by both short path and long path propagation. • Short hop sky-wave propagation on the 10-meter band is a good indicator of the possibility of sky-wave propagation on the 6-meter band.

25. G3 … Radio Wave PropagationG3C • Ionospheric layers • The D layer of the ionosphere is closest to the surface of the Earth • The ionospheric D layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz • The F2 region be expected to reach its maximum height at your location at noon during the summer • The F2 region is mainly responsible for the longest distance radio wave propagation because it is the highest ionospheric region. • Ionospheric Absorption will be minimum near the maximum usable frequency (MUF).

26. G3 … Radio Wave PropagationG3C • Critical angle and frequency • The term “critical angle” means the highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions.

27. G3 … Radio Wave PropagationG3C • HF Scatter • Long distance communication on the 40, 60, 80 and 160-meter bands are more difficult during the day because the D layer absorbs these frequencies during daylight hours.

28. G3 … Radio Wave PropagationG3C • HF Scatter(cont) • HF scatter signals often sound distorted because energy is scattered into the skip zone through several radio wave paths. • A characteristic of HF scatter signals is that they have a wavering sound. Tropo Scatter Meteor Scatter

29. G3 … Radio Wave PropagationG3C • HF Scatter(cont) • The HF scatter signals in the skip zone are usually weak because only a small part of the signal energy is scattered into the skip zone. • Scatter radio wave propagation allows a signal to be detected at a distance too far for ground wave propagation but too near for normal sky wave propagation. • An indication that signals heard on the HF bands are being received via scatter propagation can be when the signal is heard on a frequency above the maximum usable frequency.

30. G3 … Radio Wave PropagationG3C • Near Vertical Incidence Sky waves • Near Vertical Incidence Sky-wave (NVIS), propagation is short distance HF propagation using high elevation angles

31. G3 … Radio Wave PropagationG3C • Near Vertical Incidence Sky waves

32. G3 … Radio Wave PropagationG3C • Dipole placement • A horizontal dipole antenna placed between 1/8 and 1/4 wavelength above the ground will be most effective for skip communications on 40 meters during the day. ⅛ - ¼ wavelength above ground

33. G3 … Radio Wave PropagationG3C • Dipole placement

34. Element 3 General Class Question Pool Sub-element G3 Valid July 1, 2007 Through June 30, 2011

35. G3A01 What can be done at an amateur station to continue communications during a sudden ionospheric disturbance? • Try a higher frequency • Try the other sideband • Try a different antenna polarization • Try a different frequency shift

36. G3A02 What effect does a Sudden Ionospheric Disturbance (SID) have on the daytime ionospheric propagation of HF radio waves? • It disrupts higher-latitude paths more than lower-latitude paths • It disrupts signals on lower frequencies more than those on higher frequencies • It disrupts communications via satellite more than direct communications • None, because only areas on the night side of the Earth are affected

37. G3A03 How long does it take the increased ultraviolet and X-ray radiation from solar flares to affect radio-wave propagation on the Earth? • 28 days • Several hours depending on the position of the Earth in its orbit • Approximately 8 minutes • 20 to 40 hours after the radiation reaches the Earth

38. G3A04 What is measured by the solar flux index? • The density of the sun's magnetic field • The radio energy emitted by the sun • The number of sunspots on the side of the sun facing the Earth • A measure of the tilt of the Earth's ionosphere on the side toward the sun

39. G3A05 What is the solar-flux index? • A measure of the highest frequency that is useful for ionospheric propagation between two points on the Earth • A count of sunspots which is adjusted for solar emissions • Another name for the American sunspot number • A measure of solar activity at 10.7 cm

40. G3A06 What is a geomagnetic disturbance? • A sudden drop in the solar-flux index • A shifting of the Earth's magnetic pole • Ripples in the ionosphere • A significant change in the Earth's magnetic field over a short period of time

41. G3A07 Which latitudes have propagation paths that are more sensitive to geomagnetic disturbances? • Those greater than 45 degrees North or South latitude • Those between 5 and 45 degrees North or South latitude • Those at or very near to the equator • All paths are affected equally

42. G3A08 What can be an effect of a geomagnetic storm on radio-wave propagation? • Improved high-latitude HF propagation • Degraded high-latitude HF propagation • Improved ground-wave propagation • Improved chances of UHF ducting

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

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

45. G3A11 How long is the typical sunspot cycle? • Approximately 8 minutes • Between 20 and 40 hours • Approximately 28 days • Approximately 11 years

46. G3A12 What is the K-index? • An index of the relative position of sunspots on the surface of the sun • A measure of the short term stability of the Earth’s magnetic field • A measure of the stability of the sun's magnetic field • An index of solar radio flux measured at Boulder, Colorado

47. G3A13 What is the A-index? • An index of the relative position of sunspots on the surface of the sun • The amount of polarization of the sun's electric field • An indicator of the long term stability of the Earth’s geomagnetic field • An index of solar radio flux measured at Boulder, Colorado

48. G3A14 How are radio communications usually affected by the charged particles that reach the Earth from solar coronal holes? • HF communications are improved • HF communications are disturbed • VHF/UHF ducting is improved • VHF/UHF ducting is disturbed

49. G3A15 How long does it take charged particles from Coronal Mass Ejections to affect radio-wave propagation on the Earth? • 28 days • 14 days • The effect is instantaneous • 20 to 40 hours

50. G3A16 What is a possible benefit to radio communications resulting from periods of high geomagnetic activity? • Aurora that can reflect VHF signals • Higher signal strength for HF signals passing through the polar regions • Improved HF long path propagation • Reduced long delayed echoes