ESAT RHM 2 - PART 1
RF Antenna Theory Quiz
Test your knowledge on RF antennas with this comprehensive quiz designed for enthusiasts and professionals in the field of radio frequency communications. This quiz contains 122 questions covering various aspects of antennas, their design, fun
Whether you're a student, a teacher, or an industry professional, you'll find valuable insights that can enhance your understanding of RF engineering.
- Comprehensive coverage of RF antennas
- Multiple choice questions for effective assessment
- Immediate feedback on your answers
Which of the following is not a reason why most half-wave antennas are mounted horizontally at low frequencies?
physical construction is easier
more cost-effective
mounting is easier
support is easier
The shape of the electromagnetic energy radiated from or received by an antenna is called the
signal shape
electromagnetic pattern
radiation pattern
antenna pattern
Antennas that transmit an equal amount of energy in the horizontal direction are called
Bi-directional
unidirectional
Omnidirectional
unilateral
The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as
Focal factor
permittivity
directivity
horizontal range
A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form a
parasitic array
bi-directional array
half-wave dipole
counterpoise
To obtain efficient power transmission from a transmitter to an antenna requires:
High load impedance
Low ohmic resistance
Matching of impedance
Inductive impedance
To obtain efficient transfer of power from a transmitter to an antenna, it is important that there is a:
high load impedance
Matching of impedance
Proper method of balance
low ohmic resistance
If an antenna is correctly matched to a transmitter, the length of transmission line:
must be a full wavelength long
Must be an odd number of quarter-wave
Must be an even number of half-waves
will have no effect on the matching
The reason that an RF transmission line should be matched at the transmitter end is to:
ensure that the radiated signal has the intended polarization
transfer the maximum amount of power to the antenna
Prevent frequency drift
Overcome fading of the transmitted signal
If the center impedance of a folded dipole is approximately 300 ohms, and you are using RG8U (50 ohms) coaxial lines, what is the ratio required to have the line and the antenna matched?
2:1
4:1
10:1
6:1
Atmospheric________of RF energy with no reflection or refraction that adversely affects long distance communications. This does not allow any reflection or refraction.
Absorption
Attenuation
Diffraction
None of the choices
The portion of a cycle measured from a reference line to a maximum value above (or to a maximum value below) the line.
phase
Frequency
Amplitude
Wavelength
The angle between the reflected wave and the normal.
angle of reflection
critical angle
acceptance angle
elevation angle
The unit used to define the wavelength of light waves.
Meter
Angstrom
Millimeter
Mil
A conductor or set of conductors used either to radiate rf energy into space or to collect rf energy from space.
Reflector
radiator
coaxial line
Antenna
Find the characteristics impedance of polyethylene, which has a dielectric constant of 2.3.
164 Ω
249 Ω
867 Ω
572 Ω
The dielectric strength of air is about 3 MV/m, Arcing is likely to take place at field strengths greater than that. What is the maximum power density of an electromagnetic wave in air?
23.9GW/m^2
23.9GW/m^2
11.9GW/m^2
11.9GW/m^2
A power of 100 W is supplied to an isotropic radiator. What is the power density at a point 10 km away?
79.6 nW/m^2
0.1 nW/m^2
32.2 nW/m^2
None of the above
A transmitter has a power output of 150 W at a carrier frequency of 325 MHz. It is connected to an antenna with a gain of 12 dBi. The receiving antenna is 10 km away and has a gain of 5 dBi. Calculate the power delivered to the receiver, assuming free-space propagation. Assume also that there are no losses or mismatches in the system.
-21.43dBW
-65.21dBW
-63.88dBW
-86.796 dBW
The change in the propagation constant for different waves is called
diffraction
constructive interference
Dispersion
Destructive interference
The change in the propagation constant for different wavelengths is called
Chromatic dispersion
Modal interference
Modal dispersion
Both chromatic and modal dispersion
Modes traveling in an optical fiber are said to be ________.
parallel
transverse
Parallel or transverse
In phase
The electric field is perpendicular to the direction of propagation and the magnetic field is in the direction of propagation.
TM
TE
TE and TM mode
None of the choices
An antenna made up of a driven element and one or more parasitic elements is generally referred to as a
Hertz antenna
Marconi antenna
Collinear antenna
Yagi antenna
Which antennas usually consist of two or more half-wave dipoles mounted end to end?
Hertz
Marconi
Collinear
Yagi
A stacked collinear antenna consisting of half-wave dipoles spaced from one another by one-half wavelengths is the
Broadside array
End-fire array
Wide-bandwidth array
Parasitic array
When the characteristic impedance of the transmission line matches the output impedance of the transmitter and the impedance of the antenna itself,
the SWR will be 10:1
the SWR will be 1:10
minimum power transfer will take place
Maximum power transfer will take place
What does horizontal wave polarization mean?
The electric and magnetic lines of force of a radio wave are perpendicular to the earth's surface
The electric lines of force of a radio wave are perpendicular to the earth's surface
The electric lines of force of a radio wave are parallel to the earth's surface
The magnetic lines of force of a radio wave are parallel to the earth's surface
What does vertical wave polarization mean?
The magnetic lines of force of a radio wave are perpendicular to the earth's surface
The electric lines of force of a radio wave are perpendicular to the earth's surface
The electric lines of force of a radio wave are perpendicular to the earth's surface
The electric lines of force of a radio wave are perpendicular to the earth's surface
What electromagnetic wave polarization does a Yagi antenna have when its elements are parallel to the earth's surface?
Helical
Horizontal
Vertical
Circular
What electromagnetic wave polarization does a half-wavelength antenna have when it is perpendicular to the earth's surface?
Circular
Horizontal
Parabolical
Vertical
Polarization of an antenna is determined by:
the height of the antenna
The electric field
the type of antenna
The magnetic field
A one-quarter wavelength of coaxial or balanced transmission line of a specific impedance connected between a load and a source in order to match impedances is
A balun
An autotransformer
a Q section
Dummy load
The microstrip lines shown in the circuit are used for
low-noise amplification
Decoupling to prevent feedback
impedance matching and tuning
signal coupling
Small wire loop inductors and capacitors are used to provide
low-noise amplification
decoupling to prevent feedback
decoupling to prevent feedback
signal coupling
Hollow metal conducting pipes designed to carry and constrain the electromagnetic waves of a microwave signal are
Wavetraps
Waveguides
Traveling wave tubes
Microwave tubes
An array that radiates in opposite directions along the line of maximum radiation.
An array that radiates in opposite directions along the line of maximum radiation.
An array that radiates in opposite directions along the line of maximum radiation.
bidirectional array
Directional array
Connecting the center of an antenna to a transmission line, which is then connected to the final (output) stage of the transmitter.
Feeding
Center feed method
End feed method
Output feed method
A type of transmission line that contains two concentric conductors.
Balance line
Coaxial line
Twin lead
Ladder
An array system that uses the characteristics of more than one array.
Mixed array
Single array
Multi array
combination array
A wave produced by combining two or more pure tones at the same time.
multi wave
simple wave
complex wave
Square wave
A transmitter has a power output of 10 W at a carrier frequency of 250 MHz. It is connected by 10 m of a transmission line having a loss of 3 dB/100 m to an antenna with a gain of 6 dBi. The receiving antenna is 20 km away and has a gain of 4 dBi. There is negligible loss in the receiver feedline, but the receiver is mismatched: the antenna and line are designed for a 50 Ω impedance, but the receiver input is 75 Ω. Calculate the power delivered to the receiver, assuming free-space propagation.
-65.21 dBW
-63.88 dBW
-78.43 dBW
-86.796 dBW
A radio wave moves from air (ϵr= 1) to glass (ϵr=7.8). Its angle of incidence is 30°. What is the angle of refraction?
10.3°
22.4°
19.3°
32.1°
The critical frequency at a particular time 11.6 MHz. What is the MUF for a transmitting station if the required angle of incidence for propagation to a desired destination if 70°?
31.7 MHz
32.6 MHz
97.1 MHz
33.9 MHz
A taxi company uses a central dispatcher, with an antenna at the top of a 15 m tower, to communicate with taxicabs. The taxi antennas are on the roofs of the cars, approximately 1.5 m above the ground. Calculate the maximum communication distance between the dispatcher and a taxi.
20 km
21 km
22 km
23 km
Determine the ghost width on a TV screen 15 in, wide when a reflected wave results from an object 1/2 mi “behind” a receiver.
1.51 in
2.11 in
3.22 in
4.97 in
The magnetic field is perpendicular to the direction of propagation.
TM
TE
TE and TM mode
None of the choices
_______ penetrate the cladding only slightly and the electric and magnetic fields are concentrated near of the center fiber.
high-order modes
Low-order modes
Both low-order and high-order modes
None of these choices
This penetrate further into the cladding material and the electrical and magnetic fields are distributed more toward the outer edges of the fiber.
low-order modes
high-order modes
high-order modes
high-order modes
Leaky modes:
multiply power as they propagate along the fiber
Gain power as they propagate along the fiber
lose power as they propagate along the fiber
divide power as they propagate along the fiber
It determines how many modes a fiber can support.
V index
Propagation mode
Critical frequency
Normalized frequency
53. Part of an antenna array.
Bay
. shore
Coast
Bank
54. The opposite of resistance in transmission lines. The minute amount of resistance that is present in the insulator of a transmission line.
Impedance
Conductance
Admittance
Reactance
55. The I^2R loss in a conductor caused by the current flow through the resistance of the conductor.
A. Copper loss
B. Dielectric loss
C. Radiation loss
D. Induction loss
56. A network of wire that is connected to a quarter-wave antenna at one end and provides the equivalent of an additional 1/4 wavelength.
Coaxial line
Ground screen
Counterpoise
top loading
57. The peak of the positive alternation (maximum value above the line) of a wave.
A. trough
B. summit
C. zenith
D. crest
58. For an isotropic antenna radiating 100 W of power, determine power density 1000 m and 2000 m from the source.
A. 7.96 µW/m^2 and 15.92 µW/m^2
A. 7.96 µW/m^2 and 15.92 µW/m^2
C. 100 µW/m^2 and 200 µW/m^2
D. 100 µW/m^2 and 25 µW/m^2
59. A line-of-sight radio link operating at a frequency of 6 GHz has a separation of 40 km between antennas. An obstacle in the path is located 10 km from the transmitting antenna. By how much must the beam clear the obstacle?
11.6 m
32.1 m
29.4 m
16.9 m
60. Find the cutoff frequency for the TE10 mode in an air-dielectric waveguide with an inside cross section of 2 cm by 4 cm. Over what frequency range is the dominant mode the only one that will propagate?
A. 7.5 x 10^9 Hz; 3.75 GHz to 7.5 GHz
B. 3.75 × 10^9 Hz; 3.75 GHz to 7.5 GHz
C. 5 x 10^9 Hz; 1.875 GHz to 15 GHz
D. None of the above
61. Find the group velocity and phase velocity for the waveguide with TE10 mode with an inside cross section of 2 cm by 4 cm, at a frequency of 5 GHz.
A. 454 × 10^6 m/s; 1.98 × 10^8 m/s
B. 402 x 10^6 m/s; 2.23 x 10^8 m/s
C. 318 x 10^6 m/s; 2.82 x 10^8 m/s
D. 198 × 10^6 m/s; 4.54 × 10^8 m/s
62. A waveguide has a cutoff frequency for the dominant mode of 10 GHz. Two signals with frequencies of 12 and 17 GHz propagate down a 50 m length of the guide. Calculate the group velocity for each and the difference in arrival time for the two.
A. 242.6×10^6 m/s; 165.8×10^6 m/s; 95.5 ns
B. 165.8×10^6 m/s; 242.6×10^6 m/s; 95.5 ns
C. 112x10^6 m/s; 233x10^6 m/s; 32.2 ns
D. None of the above
63. The core size of single mode fibers is typically around
A. 10 to 100 mm
B. 8 to 10 cm
C. 10 to 100 um
D. 8 to 10 um
64. Single mode fibers are capable of transferring higher amounts of data due to _____?
A. Low fiber dispersion
B. Bigger core diameter
C. High fiber dispersion
D. Smaller cladding diameter
65. The number of modes propagated depends on ________ in multimode fibers.
A. Core size
B. Numerical aperture
C. Both core size and numerical aperture
D. None of the choices
66. What happens as the number of mode increases in multimode fibers?
A. The effect of modal dispersion decreases
B. The effect of modal dispersion increases
C. The index profile changes
D. The critical angle increases
67. In fiber, attenuation is mainly a result of ______.
A. scattering
B. Bending losses
C. Light absorption
D. All of the choices
68. A microwave component which is used to interconnect two sections of waveguide is the
A. T section
B. Curved section
C. Choke joint
D. Tapered wedge
69. A waveguide like device that acts as a high-Q parallel resonant circuit is a
A. microstrip
B. klystron
C. horn
D. Cavity resonator
70. A three-port microwave device used for coupling energy in only one direction around a closed loop is a
A. circulator
B. joint
C. terminator
D. Cavity resonator
71. Which of the following diodes is not typically used in the microwave region?
A. point-contact
B. standard PN
C. Schottky
D. Hot carrier
72. Which of the following diodes does not oscillate due to negative-resistance characteristics?
A. tunnel
B. SCR
C. Gunn
73. Adding a series inductance to an antenna would:
A. Increase the resonant frequency
B. Have little effect
C. Decrease the resonant frequency
D. Have no change on the resonant frequency
74. What is a parasitic beam antenna?
A. An antenna where the driven element obtains its radio energy by induction or radiation from director elements
B. An antenna where all elements are driven by direct connection to the feed line
C. An antenna where some elements obtain their radio energy by induction or radiation from a driven element
D. An antenna where wave traps are used to magnetically couple the elements
75. How can the bandwidth of a parasitic beam antenna be increased?
A. Use traps on the elements
B. Use larger diameter elements
C. Use tapered-diameter elements
D. Use closer element spacing
76. If a slightly shorter parasitic element is placed 0.1 wavelength away from an HF dipole antenna, what effect will this have on the antenna's radiation pattern?
A. A major lobe will develop in the horizontal plane, parallel to the two elements
B. A major lobe will develop in the horizontal plane, toward the parasitic element
C. A major lobe will develop in the vertical plane, away from the ground
D. The radiation pattern will not be affected
77. If a slightly longer parasitic elementis placed 0.1 wavelength away from an HF dipole antenna, what effect will this have on the antenna's radiation pattern?
A. A major lobe will develop in the horizontal plane, parallel to the two elements
B. A major lobe will develop in the vertical plane, away from the ground
C. A major lobe will develop in the horizontal plane, away from the parasitic element, toward the dipole
D. The radiation pattern will not be affected
78. The maximum frequency at which a radio wave can be transmitted vertically and still be refracted back to earth.
A. OWF
B. MUF
C. fc
D. fr
79. The ratio of maximum to minimum current along a transmission line.
A. VSWR
B. SWR
C. ISWR
D. Γ
80. Reduction of energy by absorption.
A. damping
B. Flywheel effect
C. attenuation
D. All of the choices
81. The device that responds to a wave or disturbance.
A. detector
B. diffusion
C. directional
D. Dielectric loss
82. The losses resulting from the heating effect on the dielectric material between conductors.
A. Copper loss
B. Dielectric loss
C. Radiation loss
D. Induction loss
83. Find the characteristics impedance and At what frequency will it oscillate in the transmit-time mode?
A. 360 Ω; 7.11 cm
B. 570 Ω; 9.08 cm
C. 300 Ω;
D. None of the above
84. A Gunn device has a thickness of 7 µm. At what frequency will it oscillate in the transmit-time mode?
28.6 GHz
21.45 GHz
14.3 GHz
None of the above
85. Calculate the power gain and bandwidth of a microwave dish antenna with a 3m mouth diameter when used at 10 GHz.
A. 101.5 dB; 3.2 deg
B. 47.8 dB; 0.7 deg
C. 32.0 dB; 1.1 deg
D. 60.26 dB; 0.01 deg
86. For a rectangular waveguide with a wall separation of 3 cm and a desired frequency of operation of 6 GHz, determine the cutoff wavelength.
A. 6 cm
B. 8 cm
C. 10 cm
D. 3 cm
87. A radar transmitter has a power of 10 kW and operates at a frequency of 9.5 GHz. Its signal reflects from a target 15 km away with a radar cross section of 10.2m^2. The gain of the antenna is 20 dBi. Calculate the received signal power.
A. 22.1 fW
B. 11.2 fW
C. 10.1 fW
D. 9.76 fW
88. It is the loss of optical power as light travels along the fiber.
A. Absorption
B. Dispersion
C. Attenuation
D. Scattering
89. The ratio of optical input power to the optical output power.
A. Absorption
B. Dispersion
C. Attenuation
D. Scattering
90. The portion of attenuation resulting from the conversion of optical power into another energy form, such as heat.
A. Absorption
B. Dispersion
C. Attenuation
D. Scattering
91. Determine the factor/s that causes absorption in optical fiber.
A. The extrinsic (presence of impurities) fiber-material properties
B. The intrinsic or basic fiber-material properties
C. Imperfections in the atomic structure of the fiber material
D. All of the choices
92. Caused by basic fiber-material properties.
A. Extrinsic absorption
B. Total internal reflection
C. Bending loss
D. Intrinsic absorption
93. A thin piece of N-type gallium arsenide or indium phosphide semiconductor which forms a special resistor when voltage is applied to it is the
A. Tunnel diode
B. PIN diode
C. Gunn diode
D. Varactor diode
94. A microwave vacuum tube using cavity resonators to produce velocity modulation of an electron beam which produces amplification is
A. A klystron
B. magnetron
C. A cathode-ray tube
D. traveling-wave tube
95. The original signal being transmitted from the earth station to the satellite is called the
A. transponder
B. originator
C. uplink
D. downlink
96. The transmitter-receiver combination in the satellite is known as a
A. transponder
B. transceiver
C. Telephonic unit
D. repeater
97. Most communication satellites operate in the
A. high-frequency spectrum
B. VHF spectrum
C. UHF spectrum
D. Microwave frequency spectrum
98. If an antenna is made longer, what happens to its resonant frequency?
A. It decreases
B. It increases
C. It stays the same
D. It disappears
99. If an antenna is made shorter, what happens to its resonant frequency?
A. It stays the same
B. It increases
C. It disappears
D. It decreases
100. The wavelength for a frequency of 25 MHz
A. 15 meters (49.2 ft)
B. 4 meters (13.1 ft)
C. 12 meters (39.4 ft)
D. 32 meters (105 ft)
100. The wavelength for a frequency of 25 MHz is:
A. 15 meters (49.2 ft)
B. 4 meters (13.1 ft)
C. 12 meters (39.4 ft)
D. 32 meters (105 ft)
99. If an antenna is made shorter, what happens to its resonant frequency?
A. It stays the same
B. It increases
C. It disappears
D. It decreases
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