Introduction Flashcards
1
Q
Describe Direct waves
State the frequency bands
Range of frequencies
Factors effecting the range
A
- Line of Sight communications
- VHF = 30MHz - 300Mhz
- UHF = 300MHz - 3GHz
- Obstacles/Distance to horizon/Altitude of Tx and Rx
2
Q
Explain Optimum Working Frequency
A
Highest frequency that would be used for sky wave communications.
3
Q
List the two types of Atmospheric Attenuation
A
- Absorption
-Due to oxygen and water vapour - Scattering
-Due to water droplets in rain and fog
4
Q
List the causes of external noise and interference
A
Atmospheric Noise
Cosmic Noise
Accidental Interference
Deliberate Interference
5
Q
Explain Maximum Usable Frequency
A
Highest frequency that could be used for sky wave communications
6
Q
Describe Ground Waves
State the frequency bands
Range of frequencies
Factors effecting the range
A
- FOLLOWS THE CURVATURE OF THE EARTH
- VLF/LF/MF
- Less than 3MHz
- Terrain type and transmitter power
7
Q
Describe Sky waves
State the frequency bands
Range of frequencies
Factors effecting the range
A
- WAVES WHICH USE THE IONSPHERE
- HF
- 3 MHz to 30 MHz
- Condition of the ionosphere/Transmitter power/Frequency
8
Q
Commercial quality speech frequencies
A
300HZ-3KHz
