# MCQs in Communications Engineering Part 2

Compiled Miscellaneous Multiple Choice Questions in Communications Engineering Part 2 of the series. Familiarize each and every questions compiled here in Preparation for the ECE Board Exam

This is the Miscellaneous Multiples Choice Questions Part 2 of the Series in Communications Engineering. 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 past Board Questions in Communications Engineering field (Electronics Systems and Technologies). In the actual board, you have to answer 100 items in Electronic Systems and Technologies within 5 hours. You have to get at least 70% to pass the subject. Electronic Systems and Technologies is 30% of the total 100% Board Rating along with Mathematics (20%), General Engineering and Applied Sciences (20%) and Electronics Engineering (30%).

### The Series

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

Miscellaneous Communications Engineering 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

### Continue with Part II of the Series

Choose the letter of the best answer in each questions.

51. Calculate the amount of frequency deviation caused by a limited noise spike that still causes an undesired phase shift of 40 degrees when the input frequency is 15 kHz.

• A. 12.40 kHz
• B. 10.47 kHz
• C. 13.29 kHz
• D. 14.45 kHz

52. Which of the following is not a typical characteristic impedance of a coaxial cable?

• A. 50 ohms
• B. 52 ohms
• C. 45 ohms
• D. 93 ohms

53. What is emission F3F?

• A. Facsimile
• B. RTTY
• C. Modulated CW
• D. Television

54. An AM signal has the following characteristics: the carrier frequency is 150 MHz, the modulating signal frequency is 3 kHz, the carrier voltage is 60 volts, where the modulating signal (Em) is 30 volts. Find the peak voltage of the upper side frequency

• A. 10 V
• B. 15 V
• C. 30 V
• D. 7.5 V

55. Which of the following is not a basic field of FM?

• B. TV Video
• C. Mobile Communication

56. In FM Broadcasting, what is the lowest required modulating frequency?

• A. 50 Hz
• B. 30 Hz
• C. 10 Hz
• D. 5 Hz

57. For a given length of RG 8A/U coaxial cable with a distributed capacitance of 96.6 pF/m and a relative dielectric constant of 2.6, determine the velocity factor.

• A. 0.91
• B. 0.69
• C. 0.62
• D. 0.71

58. If a 500-kHz transmitter of a constant power produces a field strength of 100uV/m at a distance of 100 mi from the transmitter, what would be the theoretical field strength at a distance of 50 mi from the transmitter?

• A. 25 uV/m
• B. 200 uV/m
• C. 50 uV/m
• D. 400 uV/m

59. Fixed-frequency or channel operation of a transmitter is obtained by using a ____.

• A. LC Oscillator
• B. RC Oscillator
• C. Crystal Oscillator
• D. Synthesizer

60. Calculate the required Q for a 3 MHz carrier with sideband separation of 50 Hz and 40-dB sideband suppression.

• A. 250000
• B. 120000
• C. 125000
• D. 150000

61. ___ are types of noise generated by equipment that produces sparks.

• A. Equipment noise
• B. Atmospheric noise
• C. Space noise
• D. Internal noise

62. The radio wavelength known as ____ falls within the medium frequency range.

• A. Centimetric
• B. Decametric
• C. Hectometric
• D. Myriametric

63. When the power ratio of input to output is 1/100, the loss of the circuit, in dB, is

• A. 20
• B. -20
• C. 10
• D. 3

64. Calculate the EIRP in dBW for a 55 W transmitter into a dipole with 85% efficiency.

• A. 16.65 dBW
• B. 13.38 dBW
• C. 16.83 dBW
• D. 18.84 dBW

65. A transistor RF power amplifier operating class C is designed to produce 50 W output with supply voltage of 90V. If the efficiency is 70%, what is the average collector current?

• A. 793 mA
• B. 952 mA
• C. 476 mA
• D. 342 mA

66. R3E modulation is sometimes used to

• A. Allow the receiver to have a frequency synthesizer
• B. Simplify the frequency stability problem in reception
• C. Reduce the power that must be transmitted
• D. Reduce the bandwidth required for transmission

67. A transmission line of unknown impedance is terminated with two different resistances, and the SWR is measured each time. With a 75-ohm termination, the SWR measures 1.5, and with a 300-ohm termination, it measures 2.65. What is the impedance of the line?

• A. 50 ohms
• B. 36 ohms
• C. 113 ohms
• D. 800 ohms

68. Indicate in which time one of the following only one sideband is transmitted:

• A. H3E
• B. A3E
• C. B8E
• D. C3F

69. It is an analog method of combining two or more analog sources that originally occupied the same frequency band in such a manner that the channels do not interfere with each other.

• A. ATM
• B. FDM
• C. TDM
• D. WDM

70. The difference between the IF and the BFO frequencies is called ___.

• A. Information signal
• B. Beat frequency
• C. Carrier signal
• D. Heterodyned signal

71. A balanced modulator is sometimes called ___.

• A. Balance ring modulator
• B. Balance resistor modulator
• C. Balance lattice modulator
• D. Any of these

72. A type of filter that receives electrical energy, converts it to mechanical vibrations and then converts the vibrations back to electrical energy at its output.

• A. Crystal filter
• B. Mechanical filter
• C. LC filter
• D. SAW filter

73. The quarter-wavelength transformer line acts as a step down transformer when the load resistance is with what relationship with the characteristic impedance of the quarter-wavelength transformer?

• A. Equal
• B. Less than
• C. Greater than
• D. None of these

74. The characteristic impedance of a microstrip is equal to ___ ohms.

• A. 50 to 200
• B. 25 to 50
• C. 100 to 200
• D. 50 to 75

75. A varactor has a maximum capacitance of 80 pF and is tuned circuit with 100 uH inductor. Find the tuning voltage necessary for the circuit to resonate at triple the frequency produced by the varactor.

• A. 7.5 V
• B. 40 V
• C. 70 V
• D. 80 V

76. Calculate the gain of a parabolic antenna using a 2.5-m diameter dish operating at 10 GHz.

• A. 57.9
• B. 67.7
• C. 52.2
• D. 46.2

77. Which of the following is NOT a color code for Category 5 UTP?

• A. Blue/white stripe and blue
• B. Orange/white stripe and orange
• C. Red/white stripe and red
• D. Brown/white stripe and brown

78. What is the major cause of fading?

• A. Phase difference
• B. Topographic variation
• C. Climate
• D. Ionospheric variation

79. A receiver produces a noise power of 200mW with no signal. The output level increases by 5W when a signal is applied. Calculate (S+N)/N in decibels.

• A. 10.14 dB
• B. 11.34 dB
• C. 13.12 dB
• D. 14.14 dB

80. An AM broadcast transmitter has a carrier power output of 50 kW. What is the total power would be produced with 90% modulation?

• A. 70.25 kW
• B. 88.15 kW
• C. 99.45 kW
• D. 66.98 kW

81. Scatter transmission is used at what frequencies?

• A. EHF and VLF
• B. HF and VHF
• C. VHF and UHF
• D. ELF and VLF

82. Why are verticals sometimes top-loaded?

• A. To resonate on high frequency
• B. To decrease the electrical length
• C. To resonate on low frequency
• D. To look better

83. In what range of frequencies are most omnidirectional horizontally polarized antennas used?

• A. VHF and UHF
• B. HF and VHF
• C. UHF and HF
• D. LF and MF

84. A transmitter supplies 25 W to a load through a line with SWR of 4:1. Find the power absorbed by the load.

• A. 32 W
• B. 64 W
• C. 23 W
• D. 12 W

85. What is the percent total harmonic distortion for a fundamental frequency with amplitude of 9 Vrms, second harmonic amplitude of 0.3 Vrms, and the third harmonic amplitude of 0.1 Vrms?

• A. 2.795 %
• B. 1.25%
• C. 2.5%
• D. 3.5%

86. What is the 12th octave for a 1-kHz repetitive wave?

• A. 6.012 MHz
• B. 4.096 MHz
• C. 8.89 MHz
• D. 5.045 MHz

87. What method can be used to determine the feed-point impedance of a vertical antenna?

• A. Resistance substitution
• B. Impedance matching
• C. Dissipated resistance measurement
• D. Grounding the antenna

88. The frequency band normally used to penetrate ocean depths and therefore used for communicating with submarine is ________.

• A. EHF
• B. MF
• C. HF
• D. ELF

89. Typical mode of radiation of helical antenna is

• A. End fire
• B. Normal
• C. Common mode
• D. Differential mode

90. A measure of mismatch in a transmission line

• A. Reflection coefficient
• B. Propagation delay
• C. Standing wave ratio
• D. All of these

91. Placing a metallic array on the antenna effects to increase the current at the base of the antenna, and also to make the current distribution more uniform. What is this called?\

• A. Stub matching
• B. Grounding
• D. Feeding

92. Calculate the beam width between nulls of a 2-m paraboloid reflector used at 6GHz.

• A. 14 deg
• B. 7 deg
• C. 3.5 deg
• D. 0.875 deg

93. This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts.

• A. Splicing
• B. Zoning
• C. Curving
• D. Polarizing

94. Which of the following antenna types is not designed for transmitting at 10 GHz.

• A. Horn antenna
• B. Dish antenna
• C. Zepp antenna
• D. Helical antenna

95. Two antennas have gains of 5.3 dBi and 4.5 dBd, respectively. Which has a greater gain?

• A. The first antenna has a higher gain
• B. The second antenna has a higher gain
• C. Both antennas have the same gain
• D. Cannot be determined

96. Which of the following is not a reason why most half-wave antennas are mounted horizontally at low frequencies?

• A. Physical construction is easier
• B. More cost-effective
• C. Mounting is easier
• D. Support is easier

97. Which antennas usually consist of two or more half-wave dipoles mounted end to end?

• A. Hertz
• B. Marconi
• C. Collinear
• D. Yagi

98. 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. A balun
• B. An autotransformer
• C. A Q section

99. It is the ability of the oscillator in a receiver to oscillate either above or below the selected radio frequency carrier by an amount equal to the intermediate frequency throughout the entire radio frequency band.

• A. Heterodyning
• B. Ranging
• C. Tracking
• D. Conversion

100. The capacitor used which prevents a portion of the signal from radiating from their leads

• A. Bypass
• B. Feedthrough
• C. Coupling
• D. Neutralization

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