For quiz 3 Flashcards
Radio Frequency Bands
ELF (3 - 30 Hz)
SLF (30 - 300Hz)
ULF (300 - 3000 Hz)
VLF (3 - 30 kHz)
LF (30 -300 kHz)
MF (300 - 3000 kHz)
HF (3 - 30 MHz)
VHF (30 -300 MHZ)
UHF ( 300 - 3000 MHz)
SHF (3 - 30 GHz)
EHF (30 -300 GHz)
the wave environment is free from everything except the wave itself.
Free space
The orientation of the E-field component of the TEM wave is called its ____
Polarization
If the direction remains constant with time at a fixed point in space, the field is said to be ______.
Linearly Polarized
Composed of magnetic field(H) and electric field(E)
Transverse Electrmomagnetic Wave (TEM)
The ____ of the TEM wave depends on the medium where it travels.
Velocity
Number of cycles per second
Frequency
The distance that the radio wave travels in one cycle
Wavelength
refers to the physical orientation of the electric field on space
Polarization
Types of Polarization
- Linear
- Circular
- Elliptical
- Random
E field has a particular direction in space may it be horizontal or vertical
Linear Polarization
E field is rotating about the axis of the direction of propagation
Circular polarization
Similar to circular polarization but E and H are not equal
Elliptical polarization
Polarization with no fixed pattern
Random Polarization
Line drawn along the direction of propagation of the wave
Ray
Surface of constant phase of the wave
Wavefront
ratio between electric field intensity and magnetic field intensity.
Intrinsic Characteristic Impedance
rate at which energy flows through a unit area of surface in space
Power Density
states that power density is inversely proportional to the square of the distance from the source
Inverse Square Law
The amount of voltage that will be induced by an electromagnetic wave at a specific location
Electric Field Intensity or Field Strength
The ratio of the speed of radio wave in free space to the speed of radio wave in specific medium
Index of Refraction
Bending of radio wave as it passes at a medium
Refraction
An incident wave strikes the boundary of two media and some or all of the incident power does not enter the second material
Reflection
Types of reflection
- Diffuse Reflection
- Specular Reflection
- Rayleigh Criterion
Redistribution of energy within a wavefront
Diffraction
When two waves that left one source and travelled by different paths arrive at a point
Interference
Modes of Wave Propagation
- Ground/Surface wave propagation
- Sky wave propagation
- Space wave/ LOS propagation
travels over the surface of the earth
Ground wave Propagation
- Aka ionospheric propagation
- sky waves strike the ionosphere and is reflected back to the ground
Sky wave propagation
layers of the atmosphere
1.Troposphere
2. Stratosphere
3. Ionosphere
Lowest layer and is 8-10 miles above sea level
Troposphere
Also called as isothermal region because of its constant temperature
Stratosphere
Ionized layer and low-density gas are found
ionosphere
Layers of the Ionosphere
- D - Layer
- E - Layer
- F - Layer
-Lowest layer of the ionosphere
- 30 -55 miles above the earth
- ionization begins at sunrise, peaks at local noon and ends at sundown
D-Layer
- 55-90 miles above the earth
-Aids MF
-ionization peaks at noon
-aka Kennelly-Heaviside layer
E-layer
- 90-240 miles above the Earth
- divided into two layers during daytime (F1 and F2)
F-Layer
Highest frequency that will be returned down to earth when beamed vertically upward
Critical frequency
Highest frequency that will returned down to earth at a given distance at a specific angle
Maximum Usable Frequency (MUF)
Frequency that gives the most consistent communication
Optimum Working Frequency (OWF)
apparent height of the ionized layer
Virtual Height
area that is between the outer limit of the ground wave range and the inner edge of the energy of return from the ionosphere
Skip zone
Distance between the originating site and the beginning of the atmospheric return
Skip distance
- Aka Line of Sight propagation
Space Wave propagation
refers to the boundary line beyond which direct rays of the radio waves cannot be propagated over the earth’s surface
Radio horizon
