1. Chapter 8
Antennas
Propagation
Dave Piersall, N6ORB

2. Brief Review of a few Chapter 7 Exam Questions
Lower ground reflection losses
Lower feed point impedance
Shorter Radials
Lower radiation resistance
Which of the following is an advantage of a horizontally polarized as compared to a vertically polarized HF antenna?
G9B09 Page 7-7
Lower ground reflection losses
MDARC/SATERN General Class License Course 2

3. Brief Review of a few Chapter 7 Exam Questions
42 feet
84 feet
131 feet
263 feet
What is the approximate length for a 1/2 wave
dipole antenna cut for MHz?
G9B11 Page 7-3
131 feet
MDARC/SATERN General Class License Course 3

4. Brief Review of a few Chapter 7 Exam Questions
The number of directors versus the number of reflectors
The relative position of the driven element with respect to the reflectors and directors
The power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction
The ratio of forward gain to dipole gain
What does "front-to-back ratio" mean in reference to a Yagi antenna?
G9C07 Page 7-9
The power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction
MDARC/SATERN General Class License Course 4

5. Brief Review of a few Chapter 7 Exam Questions
3 dB higher
3 dB lower
2.54 dB higher
About the same
How does the gain of a two-element delta
loop beam compare to the gain of a two-
element quad antenna?
G9C16 Page 7-12
About the same
MDARC/SATERN General Class License Course 5

6. The essence of this chapter MDARC/SATERN General Class License Course
Chapter 8 Propagation
Getting radio waves from Point A to Point B.
Solar phenomena and its effects on HF propagation.
Understanding the changes in the ionosphere and its impact for HF propagation.
The essence of this chapter
MDARC/SATERN General Class License Course 6

7. Chapter 8 8.1 The Ionosphere
Regions
The ionosphere is in the upper regions of the Earth’s atmosphere and located 30 to 300 miles above the earth surface.
The air is so thin that solar ultraviolet light can break molecules of air into individual atoms, and even strip away the outer electrons from those atoms to form electrically charged negative and positive ions.
The free electrons and charged ions can actually conduct electricity.
MDARC/SATERN General Class License Course 7

8. Chapter 8 8.1 The Ionosphere
Regions
Based on Figure 8.1 (B), Page 8-2
MDARC/SATERN General Class License Course 8

9. Chapter 8 8.1 The Ionosphere
Based on Figure 8.1 (A), Page 8-2
Regions
MDARC/SATERN General Class License Course 9

10. Chapter 8 8.1 The Ionosphere
The D Layer
Summary
30 to 60 miles in altitude.
Present only when illuminated by the sun.
Without UV light from the sun and because of closeness of the ions and free electrons, it quickly disappears at night. (This “disappearance” is its neutral state).
MDARC/SATERN General Class License Course 10

11. Chapter 8 8.1 The Ionosphere
The E Layer
Summary
60 to 70 miles in altitude.
Acts similarly to the D Layer, but since it is higher and therefore less dense than the D Layer, it persists longer after sunset before returning to the neutral state.
MDARC/SATERN General Class License Course 11

12. Chapter 8 8.1 The Ionosphere
The F Layer
Summary
100 to 300 miles in altitude.
Less dense than the D and E Layers.
During daylight splits into F1 and F2 Layers and recombines at night into a single F Layer.
Altitude of the regions is quite variable.
The stronger that the illumination is from the sun, then the higher the F2 Layer will be.
MDARC/SATERN General Class License Course 12

13. Chapter 8 8.1 The Ionosphere
Its all about the sun’s UV energy reacting with the molecules in the ionosphere and producing charged ions.
r is so thin that solar ultraviolet light can break molecules of air into individual atoms, and even strip away the outer electrons from those atoms to form electrically charged negative and positive ions.
The free electrons and charged ions can actually conduct electricity.
Summary
Ion Formation in the ionosphere
This is the result
MDARC/SATERN General Class License Course 13

14. Chapter 8 8.1 The Ionosphere
Radio waves are refracted in the ionosphere and return to Earth far from the transmitting station.
Without refraction, radio waves would pass into space.
Reflection and Absorption
Based on Figure 8.2, Page 8-3
Based on Figure 8.2, Page 8-3
MDARC/SATERN General Class License Course 14

15. Chapter 8 8.1 The Ionosphere
Radio Wave refraction depends on……
The density of the charged particles in the ionosphere
The angle at which the radio waves leave the transmitter
Reflection and Absorption
Based on Figure 8.3, Page 8-4
MDARC/SATERN General Class License Course 15

16. Chapter 8 8.1 The Ionosphere
Refracted radio waves can travel great distances
Radio waves reflected from uppermost F2 layer can travel up to 2500 miles before returning to the ground.
Radio waves reflected from the E layer can travel up to miles.
Sky-wave and Ground-wave Propagation
MDARC/SATERN General Class License Course 16

17. MDARC/SATERN General Class License Course
Chapter The Sun
The Basics
The Sun generates Ultraviolet (UV) radiation.
The amount of radiation varies over time.
Much of the variation is due to sunspots.
MDARC/SATERN General Class License Course 17

18. MDARC/SATERN General Class License Course
Chapter The Sun
Sunspots and Cycles
The typical sunspot cycle lasts 11 years.
Based on Figure 8.5, Page 8-6
MDARC/SATERN General Class License Course 18

19. Measuring Solar Activity MDARC/SATERN General Class License Course
Chapter The Sun
Measuring Solar Activity
Solar-Flux Index (SFI) – The amount of 2800 MHz (10.7 cm wavelength) radio energy from the sun. This is associated with solar UV and activity.
K Index – The short term stability of Earth’s geomagnetic field. High values indicate disturbance, disrupting HF communications.
A Index – The long term measure of the Earth’s geomagnetic field stability.
spaceweather.com
Solar-Flux Index
K Index
Examples
MDARC/SATERN General Class License Course 19

20. Assessing Propagation MDARC/SATERN General Class License Course
Chapter The Sun
Assessing Propagation
MUF - Maximum Usable Frequency
LUF - Lowest Usable Frequency
These depend on specific path, time of day, season, solar flux, and ionospheric stability.
Generally, radio waves leave the transmitting antenna at angles of 0 to 30 degrees and hit the ionosphere obliquely, requiring less bending to be returned to earth, thus frequencies above the critical frequency can be returned.
Typical MUF values
15 to 40 MHz (daytime)
3 to 14 MHz (nighttime)
MDARC/SATERN General Class License Course 20

21. MDARC/SATERN General Class License Course
Chapter The Sun
Solar Disturbances
Solar Flare - A large eruption of energy and solar material when magnetic field disruptions occur on the surface of the Sun.
Coronal Hole – A weak area in the Sun’s corona through which plasma escapes the Sun’s magnetic field.
Coronal Mass Ejection (CME) – An ejection of large amounts of material from the corona.
MDARC/SATERN General Class License Course 21

22. MDARC/SATERN General Class License Course
Chapter The Sun
Solar Disturbances
Based on Figure 8.7, Page 8-9
MDARC/SATERN General Class License Course 22

23. Geomagnetic Disturbances MDARC/SATERN General Class License Course
Chapter The Sun
Geomagnetic Disturbances
Charged particles from the Sun and the Earth’s magnetic field interact in a region called the magnetosphere.
Charged particles from a coronal hole or CME take 20 to 40 hours to reach Earth.
When they arrive they disturb the magnetosphere and increase E layer ionization, causing aurora displays and creating a geomagnetic storm disturbing HF communications.
MDARC/SATERN General Class License Course 23

24. Chapter 8 8.2 The Sun September 18th, 2015 CME
Geomagnetic Disturbances
Estimated Planetary K index over three days
September 18th, 2015 CME
MDARC/SATERN General Class License Course 24

25. Geomagnetic Disturbances MDARC/SATERN General Class License Course
Chapter The Sun
Geomagnetic Disturbances
Aurora Forecast
MDARC/SATERN General Class License Course 9

26. Chapter 8 8.3 Scatter Modes Characteristics
Based on Figure 8.8, Page 8-10 26

27. Near Vertical Incidence Sky-wave (NVIS)
Chapter Scatter Modes
Near Vertical Incidence Sky-wave (NVIS)
Short distance MF or HF propagation using high elevation angles.
Best results with antennas 1/8 to 1/4 wave length above ground.
Based on Figure 8.8, Page 8-10 27

28. Another chapter done! Hey doc, stay tuned for Chapter 9
MDARC/SATERN General Class License Course 28