Electromagnetic Wave Propagation Quiz 1
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For COMMUNICATIONS 3 students
- 1.Ground-wave communications is most effective in what frequency range?
- A.
300 kHz to 3 MHz
- B.
3 to 30 MHz
- C.
30 to 300 MHz
- D.
above 300 MHz
- 2.The ionization causes the signal to be
- A.
Diffused
- B.
Absorbed
- C.
refracted
- D.
Reflected
- 3.The critical frequency at a particular time is 11.6 MHz. What is the MUF for a transmitting station if the required angle of incidence for propagation to a desired destination is 70°?
- A.
12.3 MHz
- B.
33.9 Hz
- C.
33.9 MHz
- D.
12.3 Hz
- 4.The ionosphere has the greatest effect on signals in what frequency range?
- A.
300 kHz
- B.
3 to 30 MHz
- C.
30 to 300 MHz
- D.
Above 300 MHz
- 5.The type of radio wave responsible for long-distance communications by multiple skips is the
- A.
ground wave
- B.
direct-wave
- C.
surface wave
- D.
Sky wave
- 6.Microwave signals propagate by way of the
- A.
direct wave
- B.
Sky wave
- C.
surface wave
- D.
Standing wave
- 7.Line-of-sight communications is not a factor in which frequency range?
- A.
VHF
- B.
UHF
- C.
HF
- D.
Microwave
- 8.A microwave-transmitting antenna is 550 ft high. The receiving antenna is 200 ft high. The maximum transmission distance is
- A.
53.2 km
- B.
53.2 ft
- C.
53.2 mi
- D.
53.2 m
- 9.To increase the transmission distance of a UHF signal, which of the following should be done?
- A.
Increase antenna gain
- B.
Increase antenna height
- C.
Increase transmitter power
- D.
Increase receiver sensitivity
- 10._________ is the amount of voltage induced in a wave by an electromagnetic wave.
- A.
Receiver voltage
- B.
Field strength
- C.
Magnetic induction
- D.
Power density
- 11.An electromagnetic wave consists of ____________.
- A.
Both electric field and magnetic field
- B.
An electric field only
- C.
A magnetic field only
- D.
Non-magnetic field only
- 12.If a radio receiver needs 1 nW/m2 of power density to function, how far away from a 1-W point source will it continue to work?
- A.
8.9 km
- B.
8.9 m
- C.
9.8 km
- D.
9.8 m
- 13.What causes tropospheric ducting of radio waves?
- A.
A very low pressure area
- B.
An aurora to the north
- C.
Lightning between the transmitting and receiving antenna
- D.
A temperature inversion
- 14.What is a wavefront?
- A.
A voltage pulse in a conductor
- B.
A current pulse in a conductor
- C.
A voltage pulse across a resistor
- D.
A fixed point in an electromagnetic wave
- 15.
- A.
595 nW
- B.
595 pW
- C.
56.9 nW
- D.
56.9 W
- 16.What causes the ionosphere to absorb radio waves?
- A.
The weather below the ionosphere
- B.
The ionization of the D region
- C.
The presence of the ionized cloud in the E region
- D.
The splitting of the E region
- 17.Which ionospheric region is closest to the Earth?
- A.
A region
- B.
E Region
- C.
D region
- D.
F region
- 18.What causes the VHF radio waves to be propagated several hundred miles over oceans?
- A.
An overcast of cirriform clouds
- B.
A high pressure zone
- C.
A polar air mass
- D.
A widespread temperature inversion
- 19.Microwave and UHF systems have which of the following in common?
- A.
Both provide fade-free communications
- B.
Both are cheaper than HF radio
- C.
They operate on the same frequency band.
- D.
They are both line-of-sight (LOS) systems.
- 20.Troposheric scatter radio
- A.
Uses molecules in the Earth’s troposphere to scatter some radio energy back to Earth
- B.
Has a limited capability for data transmission
- C.
Is not widely used commercially
- D.
All of the above
- 21.Which of the following are electromagnetic?
- A.
Radio waves
- B.
Light
- C.
Gamma rays
- D.
All of the above
- 22.Sky wave cannot be “heard”
- A.
Close to the transmitter
- B.
Far from the transmitter
- C.
In the silent zone
- D.
In the skip zone
- 23.
- A.
113 kW
- B.
113 W
- C.
131 W
- D.
131 kW
- 24.Helical antennas are often used for satellite tracking at VHF because of
- A.
Troposcatter
- B.
Ionospheric refraction
- C.
Subrefraction
- D.
The Faraday effect
- 25.Diffraction of electromagnetic waves
- A.
is caused by reflections from the ground wave
- B.
arrives only with spherical wavefronts
- C.
Will occur around edge of a sharp obstacle
- 26.The absorption of radio waves by the atmosphere depends on
- A.
Their frequency
- B.
Their distance from the transmitter
- C.
The polarization of the wave
- D.
The polarization of the atmosphere
- 27.The characteristic impedance of free space is
- A.
Not known
- B.
50Ω
- C.
infinite
- D.
377Ω
- 28.The largest frequency that will be returned to the Earth when transmitted vertically under ionospheric conditions is called the
- A.
Critical frequency
- B.
Optimum Working Frequency (OWF)
- C.
Maximum Usable Frequency (MUF)
- D.
Skip zone
- 29.As electromagnetic waves travel in free space, only one of the following can happen to them:
- A.
Absorption
- B.
Reflection
- C.
Attenuation
- D.
Refraction
- 30.In a vacuum, the speed of light
- A.
Depends on its constant
- B.
Depends on its wavelength
- C.
Depends on its electric and magnetic field
- D.
Is a universal constant
- 31.When the magnetic field is perpendicular to the surface of the Earth, what is the polarization of the TEM wave?
- A.
Circular
- B.
Elliptical
- C.
Vertical
- D.
Horizontal
- 32.What is the period of the solar cycle in which great electrical disturbance will occur?
- A.
Every 11 years
- B.
Every 4 years
- C.
Every 5 years
- D.
Every 10 years
- 33.Ducting occurs in which region of the atmosphere?
- A.
F2
- B.
Stratosphere
- C.
Troposphere
- D.
Ionosphere
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