ECE Board
Exam April 2001
When the
electric field is perpendicular to the surface of the earth, what is the
polarization of the electromagnetic wave?
Vertical
ECE Board
Exam November 2000
At what
angle would you find the propagation direction in an xy plane . if the electric
field is at 180 degrees from a reference zero degree vertical axis?
90
ECE Board
Exam April 2000
Which of the following is referred to as the electromagnetic spectrum
range of infrared signals?
0.01
millimeter
– 0.70 micrometer
ECE Board Exam November 1999
Which of the following conditions can cause tropospheric ducting?
A stable high-pressure system
ECE Board Exam April 1999
In study of wave propagation, a condition at which zero absorption of
radio wave is describes as
Free space medium
ECE Board Exam November 1998
Determine from the following radio frequency that falls under the
very high frequency band of the radio spectrum.
235.50 MHz
ECE Board Exam April 1998
At what distances is VHF propagation normally limited?
Around 500 miles
ECE Board Exam November 1997
Production of radiation by a radio transmitting station
Emission
ECE Board Exam April 1997
When waves bend away from straight line of travel, it is called
Refraction
ECE Board Exam November 1996
An electromagnetic wave consists of
Both electric and magnetic
fields
ECE Board Exam March 1996
_________ occurs when microwave beam is at a point of grazing over an
obstacle.
Diffraction
ECE Board Exam April 2001
Why are VHF or UHF radio signals which are transmitted towards the
mountain or high structure received a distant point in different locations?
Due to reflection caused by
object
ECE Board Exam November 2000
The medium frequency (MF) band
is in the spectrum range of
0.3 to 3 MHz
ECE Board Exam April 2000
The highest frequency where refracted signals are returned to the eath
at a desired distance with usable strength, normally referred to as the
critical frequency.
Maximum usable frequency
ECE Board Exam November 1999
Very High (radio) Frequency in the spectrum refers to _______ waves.
Metric
ECE Board Exam 1999
What is a wavefront?
A fixed point in an
electromagnetic wave
ECE Board Exam 1998
Electromagnetic waves of frequencies arbitrarily lower than 3,000 GHz
propagated in space without artificial guide.
Hertzian waves
ECE Board Exam April 1998
________ is a major cause of the sporadic-E condition.
Sunspot
ECE Board Exam November 1997
This type of transmission permits communication in the frequency
range from 30 to 60 MHz over distance from about 1000 to 2000 km.
Ionospheric scatter
ECE Board Exam April 1997
Highest frequency that can be used for skywave HF communications
between two given points on earth.
Maximum usable frequency
ECE Board Exam March 1996
The wavelength of light has no role in
Polarization
ECE Board Exam March 1996
Atmospheric condition is controlled by
Humidity
Pressure
Temperature
ECE Board Exam April 2001
Which part of globe is considered where sporadic-E is most common?
Equatorial regions
ECE Board Exam April 2000
Refers to the speed of radio waves traveling through space
300,000 km/sec
ECE Board Exam November 1999
What is the reason why VHF radio waves can be propagated several
hundred miles over oceans?
Widespread temperature
inversion
ECE Board Exam April 1999
Region of the atmosphere where ducting occurs
Troposphere
ECE Board Exam November 1998
Frequencies above _____ kHz, are referred to as the radio
frequencies.
20
ECE Board Exam April 1998
A radio frequency in the Ultra High Frequency band of the radio
spectrum band
0.31250 GHz
ECE Board Exam November 1997
The electric field lines in a plane perpendicular to the earth’s
surface
Vertical polarization
ECE Board Exam April 1997
Electromagnetic radiation theory was propounded by
James Clerk Maxwell
ECE Board Exam November 1996
Electromagnetic waves travel at _______ in free space
300,000 km/sec
ECE Board Exam March 1996
When the transmitting and receiving antennas are in line-of-sight of
each other, the mode of propagation is _______ wave.
Space or direct
ECE Board Exam April 2000
One of the following referred to as the long infrared signals in the
electromagnetic spectrum range.
0.010 millimeter – 1000 nanometer
ECE Board Exam April 1998
What is the period of a wave?
The time required to complete in
one cycle
ECE Board Exam April 2001
Determine the critical frequency value of an HF signal if its maximum
usable frequency is 7050.50 kHz at 35 degrees incidence.
ECE Board Exam November 1997
Any small element of space in the path of a wave may be considered as
source of secondary wavelet.
Huygen’s principle
ECE Board Exam April 1997 / November 1997
Type of transmission path that permits communication in the frequency
range from 30 to 60 MHz and over distance from about 1000 to 2000 km
Ionospheric scatter
ECE Board Exam April 1998
What propagation condition is usually indicated when a VHF signal is
received from a station over 5000 miles away?
Tropospheric ducting
ECE Board Exam November 1997
At height of 180 km above the earth and existing during daylight.
F1 layer
ECE Board Exam April 1997
What is the thickest layer of the ionosphere?
F2
ECE Board Exam November 1996
Tropospheric scatter uses the frequencies in the _________ band
UHF
ECE Board Exam March 1996
The lowest layer in the ionosphere.
D
ECE Board Exam April 2001
Except for ________ electromagnetic radiation or signal all others
cannot be used for communication purposes.
Infrared
ECE Board Exam April 2000
What type of signal propagation increases the distance of reach as
you select a higher frequency?
HF
ECE Board Exam April 1998
In radio high frequency communications, the higher the radio
frequency the __________
Longer it can reach
ECE Board Exam November 1997
An electromagnetic wave is ________ polarized when the electric field
lies wholly in one plane containing the direction of propagation.
Linearly
ECE Board Exam April 1997
Distance traveled by a wave in the time of one cyvle.
Wavelength
ECE Board Exam March 1996
In what region of the world is sporadic-E most prevalent?
The equatorial regions
ECE Board Exam April 2001
A possible type of propagation occurring if a weak and distorted
signal from a distant station on a frequency that is closed to the maximum
usable frequency is received.
Sky-wave
ECE Board Exam April 2000
By how many farther does the radio-path horizon distance exceed the
geometric horizon?
More or less 15% of the distance
ECE Board Exam April 1998
What is meant by referring to electromagnetic waves as horizontally
polarized?
The electric field is parallel
to the earth
ECE Board Exam November 1997
Which of the following falls under the high frequency band of the
radio spectrum?
8.2345 MHz
ECE Board Exam April 1997
Which region of the ionosphere is mainly responsible for long distance
night time communications?
F layer
ECE Board Exam April 2000
What is the refractive index of air?
1
ECE Board Exam November 1999
Where in the spectrum band should the line of sight or direct waves
is appropriate for radio transmission and reception?
UHF
ECE Board Exam November 1998
The extremely high frequency (EHF) band is in the radio spectrum
range.
3 to 30 MHz
ECE Board Exam April 1998
What are electromagnetic wave?
A wave consisting of an
electric field and magnetic field at right angles to each other
ECE Board Exam November 1997
The electric field lies in a plane parallel to the earth’s surface.
Horizontal polarization
ECE Board Exam November 1997
A means of beyond the line of sight propagation of microwave signal
Troposcatter
ECE Board Exam April 1997
What is the effective earths radius when Ns=300?
ECE Board Exam April 1997
Which is atmospheric attenuation?
Due to water vapor and oxygen
ECE Board Exam November 2000
One of the following is not among the medium of primary
communication.
Radio
----medium of primary
communication---
Free space
Wire
Fiber optic cable
ECE Board Exam April 2000
What is the propagation condition called where scattered patches of
relatively dense ionization develop seasonally at E-layer heights?
Sporadic-E
ECE Board Exam November 1997
What is the unit of electric field strength?
V/m or N/C
ECE Board Exam April 2000
Which of the following is the best time for transequatorial
propagation?
Afternoon or early evening
ECE Board Exam November 1999
When the electric field is parallel to the surface of the earth, what
is the polarization of the electromagnetic wave?
Horizontal
ECE Board Exam November 2000
What type of radio propagation where signal travels along the surface
of the earth?
Ground wave propagation
ECE Board Exam April 2000
Which of the following radio communications and effects, does the
auroral activity inflict?
Fluttery tone on continuous
wave signals
ECE Board Exam November 2000
Referred to as the ionospheric layer with an average height of 225 km
at night.
F2 layer
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