Book 1 Flashcards
(23 cards)
VLF Frequency Range
3khz - 30khz
LF Freqencie Range
30khz - 300khz
MF Frequency Range
300khz - 3Mhz
HF Frequency Range
3Mhz - 30Mhz
VHF Frequency Range
30Mhz - 300Mhz
UHF Frequency Range
300Mhz - 3Ghz
SHF Frequency Range
3Ghz - 30Ghz
EHF Frequency Range
30Ghz - 300Ghz
What Frequencies Bands are Ground Waves
VLF, LF, MF
What are the Attentuation Factors
- Depends on the frequency
- Conductivity of the earth
- Premativity of the earth
What Frequency band is a Sky Wave
HF
What are the factors effecting Sky Waves?
- Condition of the ionosphere
- The frequency of transmission
- Transmission power
What is a Critical Frequency?
The highest frequency a Sky Wave can travel vertically before returning to earth
What is Skip Distance?
The closest point of return for a given frequency
What is Dead Space?
The area between the furthest point travelled vertically by the ground way and the first point of return of the Sky Wave
What is a Critical Angle?
The smallest angle that will cause the Sky Wave to return to earth
What is a Maximum Usable Frequency (MUF)?
The highest frequency that could be used to establish communication between two points using the Sky Wave.
What is the MUF determined by?
The MUF is determined by the angle of incidence and the critical frequency.
What is the formula for MUF?
MUF = Fcrit/cos(angle)
What is the Optimim Working Frequency (OWF)?
The OWF is the highest frequency that would be used in practise to establish communication between two points using the Sky Wave.
What is the OWF percentage?
85%
How does a Direct (Space) wave travel to an aerial?
The direct (space) wave must travel from the transmitting aerials in a straight line to the revieving aerial, also known as ‘line of sight’.
Factors effecting EM waves?
- External Noise and interference
- Atmospheric attenuation
