MCQs in Microwave Communications Part II

This is the Multiples Choice Questions Part 2 of the Series in Microwave Communications - as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

Online Questions and Answers Topic Outline

• MCQs in Basic Principles of Microwave Communications
• MCQs in Electro-Optics
• MCQs in Photonics
• MCQs in Optoelectronics
• MCQs in Electromagnetics
• MCQs in Avionics, Aerospace, Navigational and Military Applications
• MCQs in Medical Electronics
• MCQs in Cybernetics
• MCQs in Biometrics

MCQs in Microwave Communications and Principles Series

Following is the list of multiple choice questions in this brand new series:

Microwave Communications MCQs

PART 1: MCQs from Number 1 – 50                        Answer key: PART I

PART 2: MCQs from Number 51 – 100                   Answer key: PART II

PART 3: MCQs from Number 101 – 150                 Answer key: PART III

PART 4: MCQs from Number 151 – 200                 Answer key: PART IV

PART 5: MCQs from Number 201 – 250                 Answer key: PART V

PART 6: MCQs from Number 251 – 300                 Answer key: PART VI

PART 7: MCQs from Number 301 – 350                 Answer key: PART VII

PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII

PART 9: MCQs from Number 401 – 450                 Answer key: PART IX

PART 10: MCQs from Number 451 – 500                 Answer key: PART X

SEE: More Questions and Answers in Microwave Communications

Continue Practice Exam Test Questions Part II of the Series

51. Which ferrite device can be used instead of a duplexer to isolate a microwave transmitter and receiver when both are connected to the same antenna?

• A. Isolator
• B. Magnetron
• C. Simplex
• D. Circulator

52. The pulse frequency is equal to

• A. Duty cycle/pulse width
• B. The reciprocal of the pulse repetition rate
• C. Pulse width x peak power/average power
• D. All of these

53. In a radar set, a blocking oscillator can be used to

• A. Act as the local oscillator converter stage
• B. Provide the sweep voltage for the PPI tube
• C. Produce a trigger pulse for the transmitter
• D. As a single local oscillator converter stage

54. The intensity of the echoes (target definition) on a PPI display is determined by the

• A. Radio frequency
• B. Pulse frequency and antenna rotation rate
• C. Duty cycle
• D. Average power

55. A duplexer circuit allows a transmitter and a receiver to operate from the same antenna with virtually no interaction. This circuit may be replaced by a (an)

• A. loss waveguide
• B. circulator
• C. isolator
• D. gyrator

56. Which of the following frequencies are used by a class-C Emergency Position-Indicating Radio Beacon (E.P.I.R.B)?

• A. 156.65 MHz
• B. 121.5 MHz
• C. 156.76 MHz and 156.8 MHz
• D. All of these

57. The repetition rate of a pulsed radar system indicates the

• A. Frequency of the range-marker oscillator
• B. Reciprocal of the duty cycle
• C. Number of target echoes received on one second
• D. Frequencies of the duty cycle

58. The radar set, sensitivity-time control circuit

• A. Controls the width of the magnetron pulse
• B. Is used to increase sea return
• C. Can reduce sea-return response
• D. Discriminates between targets that are very close together.

59. Which of the following is the ferrite device that buffers a microwave source from the effects of a varying load, and thereby prevents the formation of standing waves?

• A. Circulator
• B. Duplexer
• C. Isolator
• D. Diplexer

60. Pulsed radar sets are primarily used to find the

• A. Target’s range and bearing
• B. Size and speed of a target
• C. Speed and course of a target
• D. Target’s range of speed

61. Which of the following factors is mainly concerned in the design of an antenna system for pulsed radar set?

• A. Duty cycle
• B. Radio frequency
• C. Pulse frequency
• D. Pulse length

62. In a radar set receivers, an ac AFC system may be used to

• A. Automatically maintain the correct magnetron frequency
• B. Keep the IF stages on frequency
• C. Maintain the desired klystron frequency
• D. Provide automatic control of receiver gain

63. The input signal is introduced into the traveling-wave tube at the

• A. Cathode
• B. Anode
• C. Cathode end of the helix
• D. Collector end of the helix

64. The display on the PPI scope of a radar set will have greater intensity under the following conditions

• A. Higher antenna rotation speeds
• B. Lower pulse repetition rate
• C. Lower antenna rotation speeds
• D. Both lower antenna rotation speeds and higher pulse repetition

65. The operating frequency of loran C lies within the

• A. LF band
• B. VLF band
• C. MF band
• D. HF band

66. The PPI tubes have an aquadag coating on the inside of the tube. The purpose of this coating is

• A. To act as the second anode
• B. To shield the tube magnetically
• C. To decelerate the electron beam
• D. To deflect the electron beam

67. A traveling-wave tube Is used at frequencies in the order of

• A. 30 MHz
• B. 300 MHz
• C. 8000 MHz
• D. 100 MHz

68. The main benefit of using microwaves is

• A. Lower-cost equipment
• B. Simpler equipment
• C. Greater transmission distances
• D. More spectrum space for signals

69. Radio communication are regulated in the Philippines by the

• A. DOTC
• B. KBP
• C. NTC
• D. Department of Defense

70. Which of the following is not a disadvantage of microwaves?

• A. Higher-cost equipment
• B. Line-of-sight transmission
• C. Conventional components are not usable
• D. Circuits are more difficult to analyze

71. Which of the following is a microwave frequency?

• A. 1.7 MHz
• B. 750 MHz
• C. 0.98 GHz
• D. 22 GHz

72. Which of the following is not a common microwave application?

• A. Radar
• B. Mobile radio
• C. Telephone
• D. Satellite communications

73. Coaxial cable is not widely used for long microwave transmission lines because of its

• A. High loss
• B. High cost
• C. Large size
• D. Excessive radiation

74. Stripline and microstrip transmission lines are usually made with

• A. Coax
• B. Parallel wires
• C. Twisted pair
• D. PCBs

75. The most common cross section of a waveguide is a

• A. Square
• B. Circle
• C. Triangle
• D. Rectangle

76. A rectangular waveguide has a width of 1 inch and a height of 0.6 in. Its cutoff frequency is

• A. 2.54 GHz
• B. 3.0 GHz
• C. 5.9 GHz
• D. 11.8 GHz

77. A waveguide has a cutoff frequency of 17 GHz. Which of the following signals will not be passed by the waveguide?

• A. 15 GHz
• B. 18 GHz
• C. 22 GHz
• D. 255 GHz

78. Signal propagation in a waveguide is by

• A. Electrons
• B. Holes
• C. Electric and magnetic fields
• D. Air pressure

79. When the electric field in a waveguide is perpendicular to the direction of wave propagation, the mode is said to be

• A. Vertical polarization
• B. Horizontal polarization
• C. Transverse electric
• D. Transverse magnetic

80. The dominant mode in most rectangular waveguide is

• A. TE _1.0
• B. TE _1.2
• C. TM _0.1
• D. TM _1.1

81. A magnetic field is introduced into waveguide by a

• A. Probe
• B. Dipole
• C. Stripline
• D. Capacitor

82. A half-wavelength, close section of a waveguide that acts as a parallel resonant circuit is known as a(n)

• A. Half-wave section
• B. Cavity resonator
• C. LCR circuit
• D. Directional coupler

83. Decreasing the volume of a cavity causes its resonant frequency to

• A. Increase
• B. Decrease
• C. Remain the same
• D. Drop to zero

84. __________ is a popular microwave mixer diode.

• A. Gunn
• B. Varactor
• C. Hot carrier
• D. IMPATT

85. Varactor and step-recovery diodes are widely used in what type of circuit?

• A. Amplifier
• B. Oscillator
• C. Frequency multiplier
• D. Mixer

86. Which diode is a popular microwave oscillator?

• A. IMPATT
• B. Gunn
• C. Varactor
• D. Schottky

87. Which type of diodes does not ordinarily operate with reverse bias?

• A. Varactor
• B. IMPATT
• C. Snap-off
• D. Tunnel

88. Low-power Gunn diodes are replacing

• A. Reflex klystrons
• B. TWTs
• C. Magnetrons
• D. Varactor diodes

89. Which of the following is not a microwave tube?

• A. Traveling-wave tube
• B. Cathode-ray tube
• C. Klystron
• D. Magnetron

90. In a klystron amplifier, velocity modulation of the electron beam is produced by the

• A. Collector
• B. Catcher cavity
• C. Cathode
• D. Buncher cavity

91. A reflex klystron is used as a(n)

• A. Amplifier
• B. Oscillator
• C. Mixer
• D. Frequency multiplier

92. For proper operation, a magnetron must be accompanied by a

• A. Cavity resonator
• B. Strong electric field
• C. Permanent magnet
• D. High dc voltage

93. The operating frequency of klystrons and magnetrons is set by the

• A. Cavity resonators
• B. DC supply voltage
• C. Input signal frequency
• D. Number of cavities

94. A magnetron is used only as a/an

• A. Amplifier
• B. Oscillator
• C. Mixer
• D. Frequency multiplier

95. A common application for magnetron is in

• A. Radar
• B. Satellites
• C. Two-way radio
• D. TV sets

96. In a TWT, the electron beam is density-modulated by a

• A. Permanent magnet
• B. Modulation transformer
• C. Helix
• D. Cavity resonator

97. The main advantage of a TWT over a klystron for microwave amplification is

• A. Lower cost
• B. Smaller size
• C. Higher power
• D. Wider bandwidth

98. High-power TWTs are replacing what in microwave amplifiers?

• A. MESFETs
• B. Magnetrons
• C. Klystrons
• D. IMPATT diodes

99. The most widely used microwave antenna

• A. Half-wave dipole
• B. Parabolic
• C. Hyperbolic
• D. Horn

100. ______________ is a measure of reliability expressed as the average number of hours between successive failures.

• A. MTBF
• B. MTTR
• C. Downtime
• D. Outage time

Complete List of MCQs in Communications Engineering per topic

Series of Multiple Choice Questions in Electronics Systems and Technologies

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