MCQ in Antennas Part 2 | ECE Board Exam

This is the Multiples Choice Questions Part 2 of the Series in Antennas 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

• MCQ in Basic considerations
• MCQ in Wire Radiators in Space
• MCQ in Isotropic Radiator
• MCQ in Current and Voltage Distributions
• MCQ in Resonant and Non-resonant Antennas
• MCQ in Antenna Terms and Definition
• MCQ in Antenna Gain and Resistance
• MCQ in Bandwidth, Beamwidth and Polarization
• MCQ in Grounded and Ungrounded Antennas
• MCQ in Grounding Systems and Matching Systems
• MCQ in Antenna Types
• MCQ in Directional and Non-directional Antennas
• MCQ in Microwave Antennas
• MCQ in Wideband and Special Purpose Antennas

Continue Practice Exam Test Questions Part 2 of the Series

51. The current maximum in a Marconi antenna is found at

A. the base of the antenna

B. the center of the antenna

C. some point between the base and the center of the antenna

D. the top of the antenna

52. If an antenna is too short for the wavelength being used, the effective length can be increased by adding:

A. capacitance in series

B. inductance in series

C. resistance in parallel

D. resistance in series

53. Which of the following antennas is used for testing and adjusting a transmitter for proper modulation, amplifier operation and frequency accuracy?

A. Elementary

B. Real

C. Isotropic

D. Dummy

54. The power fed to a two-bay turnstile antenna is 100 watts. If the antenna has a 2 dB power gain, what is the effective radiated power?

A. 317 watts

B. 158 watts

C. 200 watts

D. 400 watts

55. What is the gain, in dB of a helical antenna with diameter of λ/3, 10 turns at pitch of λ/4, used at 100 MHz?

A. 16

B. 41.1

C. 31.4

D. 1.25

56. How is it possible to lower the resonant frequency of Hertz dipole antenna?

A. By reducing the frequency at the transmitter

B. By connecting a capacitor in series with the antenna

C. By the connecting a resistor in series with the antenna

D. By connecting an inductor in series with the antenna

57. Which of the following antennas receive signals in the horizontal plane equality well from all directions?

A. Horizontal Hertz antenna

B. Vertical loop antenna

C. Vertical Yagi antenna

D. A vertical antenna which is a quarter-wavelength long

58. If the length of a Hertz dipole is decreased

A. its resonant frequency will be lowered its distributed inductance will be increased

B. its distributed inductance will be decreased

C. its resonant frequency will be increased

D. its distributed capacitance between the antenna and ground will be increased.

59. A final amplifier of a radio transmitter draws 250 mA of plate current when the plate supply voltage is 1400 volts. If the plate circuit efficiency is 80% and the transmitter is connected to an antenna having a feed impedance of 70 ohms, what is the antenna current at the feed-point?

A. 4.0 A

B. 2.2 A

C. 1.25 A

D. 2.0 A

60. A one-quarter wavelength shunt-fed vertical Marconi antenna

A. has maximum radiation in a vertical direction

B. must have a horizontal receiving antenna for the best reception

C. must use a receiving antenna for the best reception

D. must have a vertical receiving antenna for the best reception

61. A shunt-fed quarter-wavelength Marconi antenna

A. has maximum RF impedance to ground at its feedpoint

B. has a current null at its feedpoint

C. has a zero DC resistance to ground

D. has zero RF resistance to ground

62. The parasitic element of an antenna system will

A. decrease its directivity

B. increase its directivity

C. give the antenna unidirectional properties

D. both B and C

63. If the length of an antenna is changed from 2.5 meters to 2.8 meters, its resonant frequency will

A. increase

B. depend on the velocity factor so the resonant frequency can either be increased or decreased

C. will be unchanged

D. decrease

64. What is the effect of adding a capacitor in series with an antenna?

A. The antenna’s resonant frequency will increase

B. The antenna’s resonant frequency will decrease

C. The antenna will be physically 5% longer than its electrical length

D. A capacitor is never added in series with an antenna

65. How does the electric field strength of a standard broadcast station vary with the distance from the antenna?

A. The field strength of a standard broadcast station vary with the distance from the antenna

B. The field strength is directly proportional to the distance from the antenna

C. The field strength remains constant regardless of the distance from the antenna

D. The field strength varies inversely as the distance from the antenna

66. Stacking elements in a transmitting antenna system

A. increases the field strength at the receiving antenna

B. increases the directivity of the transmitter antenna

C. decrease the size of the lobe in the radiation pattern

D. both A and B

67. A vertical loop antenna has a

A. unidirectional radiation pattern in the horizontal plane

B. unidirectional radiation pattern in the vertical plane

C. omnidirectional radiation pattern in the horizontal plane

D. a bidirectional radiation pattern in the horizontal plane

68. In order to get maximum radiation to all surrounding points in the horizontal plane, the antenna used is a

A. vertical loop

B. vertical quarter-wavelength rod

C. array which includes parasitic elements

D. a horizontal Hertz dipole

69. What is the electrical wavelength of a 500 MHz signal?

A. 60 centimeters

B. 6 meters

C. 0.06 meter

D. 60 meters

70. If the antenna current is doubled, the field strength at a particular position is

A. doubled

B. halved

C. multiplied by a factor of four

D. divided by a factor of four

71. The rhombic antenna is primarily used for

A. ground wave propagation

B. space wave propagation

C. ionosphere scatter propagation

D. sky wave propagation

72. What antenna radiates equally in all directions?

A. Vertical antenna

B. isotropic antenna

C. Horizontal antenna

D. Dipole antenna

73. Actual height of antenna should be at least

A. one wavelength

B. half wavelength

C. quarter wavelength

D. three-fourth wavelength

74. Which antenna is not properly terminated?

A. Resonant

B. Non-resonant

C. Isotropic

D. Whip

75. ______ is an antenna array which is highly directional at right angles to the plane of the array?

A. Broadside array

B. End-fire array

C. Turnstile array

D. Log-periodic array

76. The directivity pattern of an isotropic radiator is

A. a figure-8

B. a sphere

C. a unidirectional cardioid

D. a parabola

77. An isotropic radiator is

A. in the northern hemisphere

B. an antenna high enough in the air

C. an antenna whose directive pattern is substantially incredible

D. a hypothetical, omnidirectional antenna

78. The purpose of stacking elements on an antenna.

A. Sharper directional pattern

B. increased gain

C. Improved bandpass

D. All of these

79. The advantage of using top loading in a shortened HF vertical antenna is

A. lower quality factor

B. greater structural strength

C. higher losses

D. improved radiation efficiency

80. Where are the voltage nodes in a half-wave antenna?

A. At the ends

B. Three-quarters of the way from the feed point toward the end

C. One-half of the way from the feed point toward the end

D. At the feed point

81. A theoretical reference antenna that provides a comparison for antenna measurements.

A. Marconi antenna

B. Isotropic radiator

C. Yagi-Uda array

D. Whip antenna

82. A Hertz antenna is operating on a frequency of 2182 kHz and consists of a horizontal wire that is hanged between two towers. What is the frequency of its third harmonic?

A. 727 kHz

B. 6546 kHz

C. 436 kHz

D. 6.546 kHz

83. In horizontal-dipole antenna, the polarization is

A. in the vertical direction

B. in the horizontal direction

C. circular

D. measured at the center of the antenna

84. Increasing the electrical length of an antenna means

A. add an inductor in parallel

B. add a capacitor in series

C. add an inductor series

D. add a resistor is series

85. Stacking antennas at various angles results in

A. a more omnidirectional reception

B. a more unidirectional reception

C. a less omnidirectional reception

D. an overall reception signal increase

86. What is driven element?

A. Always the rearmost element

B. Always the forward most element

C. The element fed by the transmission line

D. The element connected to the rotator

87. What is antenna bandwidth?

A. Antenna length divided by the number of elements

B. The angle between the half-power radiation points

C. The angle formed between two imaginary lines drawn through

D. The frequency range over which an antenna can be expected to operate satisfactorily

88. To lengthen an antenna electrically, add a

A. resistor

B. battery

C. condult

D. coil

89. What is the gain of an antenna over a half-wavelength dipole when it has 6 dB gain over an isotropic radiator?

A. 6.0 dB

B. 8.1 dB

C. 3.9 dB

D. 10.0 dB

90. What is the usual electrical length of a driven element in an HF beam antenna?

A. ¼ wavelength

B. ¾ wavelength

C. ½ wavelength

D. 1 wavelength

91. What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

A. It is increased

B. It is decreased

C. No change occurs

D. It becomes flat

92. To electrically decrease the length of an antenna.

A. add an inductor in series

B. add an inductor in parallel

C. add a resistor in series

D. add a capacitor in series

93. Strong interference from one particular station can be eliminated by the use of

A. noise limiters

B. squelch circuits

C. negative feedback

D. wave traps in the antenna circuitry

94. It is useful to refer to an isotropic radiator.

A. when comparing the gains of directional antennas

B. when testing a transmission line for standing wave ratio

C. when (in the northern hemisphere) directing the transmission

D. when using a dummy load to tune a transmitter

95. A disadvantage of using a trap antenna.

A. It will radiate harmonics

B. It can only be used for single-bad operation

C. It is too sharply directional at lower frequencies

D. It must be neutralized

96. The input terminal impedance at the center of a folded dipole antenna is

A. 72 Ω

B. 300 Ω

C. 50 Ω

D. 73 Ω

97. When a capacitor is connected in series with a Marconi antenna?

A. Antenna open circuit stops transmission

B. An inductor of equal value must be added

C. No change occurs to antenna

D. Antenna resonant frequency increases

98. Where are the current nodes in a half-wave antenna?

A. At the ends

B. At the center

C. Three-quarters of the way from the feed point toward the end

D. One-half of the way from the feed point toward the end

99. For a shortened vertical antenna, where should a loading coil be placed to minimize losses and produce the most effective performance?

A. As low as possible on the vertical radiator

B. Near the center of the vertical radiator

C. As close to the transmitter as possible

D. At a voltage node

100. The effect of adding parasitic elements of a Hertz dipole is to

A. make the antenna more omnidirectional

B. reduce its resonant frequency

C. increase the antenna’s power gain

D. All of these

Questions and Answers in Antennas Series

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

Complete List of MCQ in Communications Engineering per topic