HF Flashcards
What is the other band name for HF?
Decametre band
What does HF stand for?
High frequency
What is the wavelength range for HF?
100 m - 10 m
What is the frequency range for HF?
3 MHz - 30 MHz
What ITU designation is below HF?
MF
What ITU designation is above HF?
VHF
What kind of obstacles block HF frequencies?
- sunlight
- solar terminator
- sunspot
- solar activity
What are the different types of HF antenna?
- wire diapoles
- rhombic
- Yagi
- quad
- log-periodic
- curtain arrays
What are the three types of propagation HF uses?
- Ground wave
- Direct wave
- Sky wave
What is the normal maximum distance for ground wave?
Short distance <20Km
What is the normal maximum distance for direct wave?
Long distance
What is the normal maximum distance for sky wave?
Long distance
Describe the the propagation of groundwave
Follows the curvature of the earth
Describe the the propagation of direct wave
Line of sight between ground to ground or ground to air communications.
Describe the the propagation of sky wave
Uses the Ionosphere to reflect the signal back to earth
What is the layer in the earth’s atmosphere that refracts radio waves back to earth?
Ionosphere
What is the skip zone?
Where the groundwave ends and the skywave starts . Radio wave are not present in this area.
What component of the radio is responsible for the coverage area?
The angle of the antenna.
Describe the Ionosphere
The ionosphere is the ionized part of Earth’s upper atmosphere, from about 48 km to 965 km altitude. It contains multiple layers.
What is the name of the closest layer of the Ionosphere?
D
What is the name of the farthest layer of the Ionosphere?
F2
What are the most common layers used for signal propagation?
F1 & F2
