This is the Coaching materials in Transmission Lines and Antennas Part 2 as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
Transmission Lines and Antennas Coaching Materials Part 2
51. Antenna utilizing the ground as part of its resonant circuit.
52. Antenna that is complete in itself and capable of self-oscillation.
53. Radiation resistance is the ratio of
radiated power to the square of current*
54. Example of Marconi type antenna.
Quarter wave vertical tower.*
55. The gain in the direction of one of the major lobes of the radiation pattern.
56. Form of unwanted radiation working against the main beam caused by feeding a parabolic reflector with an isotropic source.
57. Type of antenna capable of transmitting (receiving) a TEM wave polarized in any direction.
58. A region within the influence of the induction field of an antenna.
59. An example of parasitic array.
60. Structure made of plastic-like composite material used to enclose the complete antenna assembly for protection against the weather and to reduce wind or snow loading.
61. The minimum antenna actual height:
62. Marconi antenna current
maximum at the base*
63. Antenna that is λ/10 long is called
64. FM uses what type of polarization?
65. In antenna, the area where the signal strength is very low.
66. Which frequency band omni-horizontally polarized antenna used?
VHF and UHF*
67. Discone antenna polarization is
68. What is the advantage of Top loading?
Improved radiation efficiency*
69. What is propagation?
Propagation means spreading out.
70. How is a wave defined as it applies to wave propagation?
A wave is a disturbance which moves through a medium.
71. What is wave motion?
A means of transferring energy from one place to another.
72. What are some examples of wave motion?
Sound waves, light waves, radio waves, heat waves, water waves.
73. What type of wave motion is represented by the motion of water?
74. What are some examples of transverse waves?
Radio waves, light waves, and heat waves.
75. What example of a longitudinal wave was given in the text?
A sound wave.
76. What are the three requirements for a wave to be propagated?
A source, medium and detector(receiver).
77. What is the law of reflection?
The law of reflection states: the angle of incidence is equal to the angle of reflection.
78. When a wave is reflected from a surface, energy is transferred. When is the transfer of energy greatest?
When the incident wave is nearly parallel with the surface.
79. When is the transfer of energy minimum?
When the incident wave is perpendicular to the surface. Also a dull (or black surface) reflects very little regardless of the angle.
80. A refracted wave occurs when a wave passes from one medium into another medium, what determines the angle of refraction?
The density of the two mediums, and the velocity of the waves.
81. What do we call the field that is created between two rods when a voltage is applied to them?
82. When current flows through a conductor, a field is created around the conductor. What do we call this field?
83. An induction field is created around a conductor when current flows through it. What do we call the field that detaches itself from the conductor and travels through space.
84. What are two basic qualifications of antennas?
Half-wave(Hertz) and Quarter-wave (Marconi)
85. What are the three parts of a complete antenna system?
Coupling device, feeder, and antenna
86. What three factors determine the type size and shape of antenna?
Frequency of operation of the transmitter, amount of power to be radiated, and general direction of the receiving set.
87. If a wave exactly the length of an antenna from one end to the other and back during the period of 1 cycle, what is the length of the antenna?
One-half the wavelength.
88. What is the term used to identify the points of high-current and high voltage on an antenna?
Current and voltage loops.
89. What is the term used to identify the points of minimum current and minimum voltage on an antenna?
Current and voltage nodes.
90. The direction of what field is used to designate the polarization of a wave?
91. If a wave’s electric lines of force rotate through 360 degrees with every cycle of RF energy, what is the polarization of this wave?
92. What type of polarization should be used at medium and low frequencies?
93. What is an advantage of using horizontal polarization at high frequencies?
Less interference is experienced by man-made noise sources.
94. What type of polarization should be used if an antenna is mounted on a moving vehicle at frequencies below 50 megahertz?
95. What is the radiation resistance of a half-wave antenna in free space?
96. A radiating source that radiates energy stronger in one direction than another is what type of radiator?
97. A radiating source that radiates energy equally in all directions is known as what type of radiator?
98. A flashlight is an example of what type of radiator?
99. What terms are often used to describe basic half-wave antennas?
Dipole, doublet and hertz.
100. If a basic half-wave antenna is mounted vertically, what type of radiation pattern will be produced?