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# MCQ in Microwave Communications Part 2 | ECE Board Exam

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.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

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

#### Continue Practice Exam Test Questions Part 2 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

Solution:

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

Solution:

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

Solution:

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

B. Pulse frequency and antenna rotation rate

C. Duty cycle

D. Average power

Solution:

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

Solution:

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

Solution:

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

Solution:

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.

Solution:

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

Solution:

60. Pulsed radar sets are primarily used to find the

A. Targetโs range and bearing

B. Size and speed of a target

C. Speed and course of a target

D. Targetโs range of speed

Solution:

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

A. Duty cycle

C. Pulse frequency

D. Pulse length

Solution:

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

Solution:

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

Solution:

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

Solution:

65. The operating frequency of loran C lies within the

A. LF band

B. VLF band

C. MF band

D. HF band

Solution:

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

Solution:

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

Solution:

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

Solution:

69. Radio communication are regulated in the Philippines by the

A. DOTC

B. KBP

C. NTC

D. Department of Defense

Solution:

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

Solution:

71. Which of the following is a microwave frequency?

A. 1.7 MHz

B. 750 MHz

C. 0.98 GHz

D. 22 GHz

Solution:

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

C. Telephone

D. Satellite communications

Solution:

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

A. High loss

B. High cost

C. Large size

Solution:

74. Stripline and microstrip transmission lines are usually made with

A. Coax

B. Parallel wires

C. Twisted pair

D. PCBs

Solution:

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

A. Square

B. Circle

C. Triangle

D. Rectangle

Solution:

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

Solution:

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

Solution:

78. Signal propagation in a waveguide is by

A. Electrons

B. Holes

C. Electric and magnetic fields

D. Air pressure

Solution:

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

Solution:

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

Solution:

81. A magnetic field is introduced into waveguide by a

A. Probe

B. Dipole

C. Stripline

D. Capacitor

Solution:

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

Solution:

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

A. Increase

B. Decrease

C. Remain the same

D. Drop to zero

Solution:

84. __________ is a popular microwave mixer diode.

A. Gunn

B. Varactor

C. Hot carrier

D. IMPATT

Solution:

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

A. Amplifier

B. Oscillator

C. Frequency multiplier

D. Mixer

Solution:

86. Which diode is a popular microwave oscillator?

A. IMPATT

B. Gunn

C. Varactor

D. Schottky

Solution:

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

A. Varactor

B. IMPATT

C. Snap-off

D. Tunnel

Solution:

88. Low-power Gunn diodes are replacing

A. Reflex klystrons

B. TWTs

C. Magnetrons

D. Varactor diodes

Solution:

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

A. Traveling-wave tube

B. Cathode-ray tube

C. Klystron

D. Magnetron

Solution:

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

Solution:

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

A. Amplifier

B. Oscillator

C. Mixer

D. Frequency multiplier

Solution:

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

Solution:

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

Solution:

94. A magnetron is used only as a/an

A. Amplifier

B. Oscillator

C. Mixer

D. Frequency multiplier

Solution:

95. A common application for magnetron is in

B. Satellites

D. TV sets

Solution:

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

A. Permanent magnet

B. Modulation transformer

C. Helix

D. Cavity resonator

Solution:

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

Solution:

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

A. MESFETs

B. Magnetrons

C. Klystrons

D. IMPATT diodes

Solution:

99. The most widely used microwave antenna

A. Half-wave dipole

B. Parabolic

C. Hyperbolic

D. Horn

Solution:

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

Solution:

#### Questions and Answers in Microwave Communications and Principles Series

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

MCQ in Microwave Communications
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQs from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQs from Number 451 โ 500                 Answer key: PART 10

### Complete List of MCQ in Communications Engineering per topic

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