319. 2006105942 320. ECE003/C11
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1. It is a metallic conductor system capable of radiating and capturing electromagnetic energy
a. transmission lines b. antenna
c. waveguides d. load
337.
2. A directional antenna with two or more elements is known as
a. folded dipole b. ground plane c. loop
d. array 338.
3. The ratio of the focal length to the diameter of the mouth of the parabola is called _____.
a. aperture b. focal point c. foci d. major axis 339.
4. The impedance of a dipole is about a. 50-ohm consist of conducting metallic tube through which high frequency electromagnetic energy is propagated
a. medium antenna using a polar mount at a latitude of 45 degrees
a. 3.2 degrees b. 1.3 degrees c. 4.2 degrees d. 6.81 degrees 342.
7. The cone angle of the flare angle of a conical horn antenna is approximately
a. 55 degrees b. 45 degrees c. 40 degrees d. 50 degrees 343.
8. Electrical energy that has escaped into free space in the form of transverse electromagnetic waves
a. Radio waves b. Frequency c. Signal d. Wavelength 344.
9. The length of the ground plane vertical at 146 MHz is
10. Using a small reflector to beam waves to the larger parabolic reflector is known as
a. Focal feed b. Horn feed c. Cassegrain feed d. Coax feed 346.
11. The plane parallel to the mutually perpendicular line in the electric and magnetic fields is called _______.
a. wavefront b. point source c. isotropic source d. rays
347.
12. What is the beamwidth of a parabolic antenna with a diameter of 5 meters and an operating frequency of 10 GHz?
a. 0.5 degrees b. 0.675 degrees c. 0.348 degrees d. 3.48 degrees 348.
13. The horizontal radiation pattern of a dipole is a
a. circle
b. figure of eight c. clover leaf d. narrow beam 349.
14. The size of antenna is inversely proportional to _______.
a. frequency b. power
c. radiation resistance d. wavelength
350.
15. A popular half – wave antenna is the a. Ground plane
b. End-fire c. Collinear d. Dipole 351.
16. Calculate the gain of a parabolic antenna using a 2.5-m radius dish operating at 10GHz.
a. 166.673 dB b. 83.7 dB c. 52.2 dB d. 45.6 dB 352.
17. It is the ratio of the radiated to the reflected energy
a. Radiation resistance b. Radiation efficiency c. Radiation constant d. Radiation antenna 353.
18. The feed mechanism in a parabolic antenna that radiates the electromagnetic energy.
a. Primary antenna b. Reflectors
c. Secondary antenna d. Focal point
354.
19. It is a polar diagram or graph representing field strengths or power densities at various angular positions relative to an antenna
a. Side lobe b. Front lobe
c. Radiation pattern d. Radiation constant 355.
20. For a transmit antenna with a radiation resistance of 72 ohms, an effective antenna resistance of 8 ohms, a directive gain of 20 and an input power of 100W, determine the antenna gain. electric field strength or power density
a. absolute radiation pattern b. relative radiation pattern c. absolute front lobe pattern d. absolute side lobe pattern
22. Calculate the characteristic impedance of a quarter – wavelength section used to connect a 300-ohm antenna to a 75-ohm line
a. 150 ohms b. 120 ohms c. 130 ohms d. 110 ohms 357.
23. Plots of field strength or power density with respect to the value at a reference point
a. absolute front lobe pattern b. relative front lobe pattern c. relative front lobe pattern d. relative radiation pattern 358.
24. What must be the height of a vertical radiator one half wavelength high if the operating frequency is 1100 kHz?
a. 120 m b. 136 m c. 115 m d. 124 m 359.
25. Lobes adjacent to the front lobe a. Diagonal lobes
b. Side lobes c. Front lobes d. Back lobes 360.
26. Lobes in a direction exactly opposite of the front lobe
a. Side lobes b. Adjacent lobes c. Front lobes d. Back lobes 361.
27. Calculate the efficiency of an antenna that has a radiation resistance of 73 ohms and an effective dissipation resistance of 5 ohms
a. 98.3% pointing from the center of the antenna in the direction of maximum radiation is called _______.
a. line of shoot b. diagonal shoot c. bisecting shoot d. antenna shoot
29. The ammeter connected at the base of a Marconi antenna has a certain reading. If this reading is increased 2.77 times, what is the increase in output power?
a. 3.45 b. 1.89 c. 2.35 d. 7.67 363.
30. Refers to a field pattern that is close to the antenna.
a. Induction field b. Far field
c. Radiation field d. Capture field 364.
31. A half-wave dipole is driven with a 5-W signal at 225 MHz. A receiving dipole 100 km. Calculate the received power into a 73-ohm receiver. amount of power that the antenna radiates.
a. Directive gain b. Antenna efficiency c. Radiation resistance d. Antenna resistance 366.
33. What is the effective radiated power of a television broadcast station if the output of the transmitter is 1000W, antenna transmission line loss is 50W, and the antenna power gain is 3?
a. 1250 W b. 2370 W c. 2130 W d. 2850 W 367.
34. It is the ratio of the power radiated by an antenna to the sum of the power radiated and the power dissipated.
a. radiation resistance b. coupling coefficient c. antenna efficiency d. antenna beamwidth 368.
369.
35. It is the ratio of the power radiated by the antenna to the total input power.
a. antenna efficiency b. reflection coefficient c. standing wave ratio d. radiation resistance 370.
36. If a 500 kHz transmitter of a constant power produces 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 200 mi from the transmitter?
a. 45 uV/m equally well in all directions is said to be _____.
38. It is the ratio of the power density radiated in a particular direction to the power density radiated to the same point by a reference antenna, assuming both antennas are radiating the same amount of power
a. power gain b. directive gain c. total gain d. system gain 373.
39. If the field intensity of 25 mV/m develops 2.7 V in a certain antenna, what is its
a. is vertical b. is horizontal c. is circular
d. cannot be determined from the information given
375.
41. If the power of a 500 kHz transmitter is increased from 150 W to 300 W, what would be the percentage change in field intensity at a given distance from the transmitter?
a. 141%
b. 150%
c. 100%
d. 133%
376.
42. It is the same with directive gain except that the total power fed to the antenna is used and the antenna efficiency is taken into account.
a. system gain b. power gain c. directive gain d. total gain 377.
43. A hip-radio telephone transmitter operates on 2738 kHz. At a certain point distant from the transmitter, the 2738 kHz signal is measured field of 147 mV/m. The second harmonic field at the same point is measured as 405 uV/m. To the nearest whole unit in decibels, how much has the harmonic
44. It is the equivalent power that an isotropic antenna would have to radiate to achieve the same power density in the chosen direction at a given point as another antenna.
a. EIRP b. ERP c. IRL d. RSL 379.
45. When the energy is applied to the antenna at a point of high – circulating current.
a. voltage-fed antenna b. power-fed antenna c. current-fed antenna d. impedance-fed antenna 380.
46. For a transmit antenna with a power gain of 10 and an input power of 100W, determine the EIRP in watts.
47. If energy is applied at the geometrical center of antenna, the antenna is said to be _____.
a. center-fed b. end-fed
c. quarterwave-fed d. halfwave-fed 382.
48. For a transmit antenna with a power gain of 10 and an input power of 100W, determine the power density at a point 10 km from the transmit antenna
a. 0.574 uW/m^2 b. 0.796 uW/m^2 c. 1.24 uW/m^2 d. 0.981 uW/m^2 383.
49. For a transmit antenna with a radiation resistance of 72 ohms, an effective antenna resistance of 8 ohms, a directive gain of 20 and an input power of 100W, determine the antenna efficiency.
50. The fields surrounding the antenna do not collapse their energy back into the antenna but rather radiate it out in space.
a. induction field b. near field c. radiation field d. magnetic field 385.
51. For receive power density of 10 uW/m^2 and a receive antenna with a capture area of 0.2 m^2, determine the captured power.
a. 0.5 uW known as ______.
a. efficiency b. accuracy c. reciprocity
d. polarization 387.
53. The length of a doublet at 27 MHz is _____.
a. 8.67 ft b. 17.3 ft c. 18.2 ft d. 34.67 ft 388.
54. Refers to the orientation of the electric field radiated from an antenna.
a. efficiency b. beamwidth c. polarization d. accuracy 389.
55. At frequencies below 2 MHz, what type of antenna is usually used?
a. Marconi antenna b. Hertzian antenna c. Hertz antenna d. Elementary doublet 390.
56. The angular separation between two half-power points in the major lobe of the antenna’s plane radiation pattern.
a. bandwidth b. polarization c. efficiency d. beamwidth 391.
57. Hertz antenna are predominantly used with frequencies above
58. Defined as the frequency range over which antenna operation is satisfactory
a. beamwidth b. channel c. bandwidth d. baseband 393.
59. One of the following is not an omnidirectional antenna.
a. Half-wave dipole b. Log-periodic d. voltage feed 395.
61. A popular vertical antenna is the _____>
a. collinear b. dipole
c. ground plane d. broadside 396.
62. The discone antenna is
a. a useful direction-finding antenna b. used as a radar receiving antenna c. circularly polarized with other
circular antennas
d. useful as a UHF receiving antenna 397.
63. The feedpoint presents and ac load to the transmission line called
a. antenna output impedance b. antenna input impedance c. feedpoint impedance d. center feed impedance 398.
64. A helical antenna is used for satellite tracking because of its
a. circular polarization b. maneuverability c. broad bandwidth d. good front to back ratio 399.
65. The simplest type of antenna.
a. Elementary doublet b. Half-wave dipole c. Quarterwave dipole d. 5/8 wavelength dipole 400.
66. Zoning is used with a dielectric antenna in order to
a. reduce the bulk of the lens b. increase the bandwidth of the lens c. permit pin-point focusing
d. correct the curvature of the
67. It is an electrically short dipole
a. short dipole b. quarterwave dipole c. half-wave dipole d. yagi antenna 404.
68. Cassegrain feed is used with parabolic reflector to
a. increase the gain of the system b. increase the bandwidth of the system c. reduce the size of the main reflector d. allow the feed to be placed at a
convenient point 405.
69. The half-wave dipole is generally referred to as ______.
a. Yagi antenna b. Hertzian antenna c. Marconi antenna d. Hertz antenna 406.
70. Top loading is sometimes used with an antenna in order to increase its
a. effective height b. bandwidth c. beamwidth d. input capacitance 407.
71. What is the directivity of a Hertz antenna?
a. 1.64 directive gain is the _______.
a. infinitesimal dipole b. isotropic antenna c. elementary doublet d. half-wave dipole 409.
73. An antenna which is one-quarter wavelength long, mounted vertically with the lower end either connected directly to ground or grounded through the antenna coupling network.
a. loop antenna b. hertzian dipole c. monopole antenna d. turnstile antenna 410.
411.
74. An antenna that is circularly polarized is the
a. helical
b. small circular loop c. parabolic reflector d. Yagi – Uda
412.
75. It is a wire structure placed below the antenna and erected above the ground.
a. ground plane b. counterpoise c. ground lines d. top hat 413.
76. Which of the following terms does not apply to the Yagi-Uda array?
a. good bandwidth b. parasitic elements c. folded dipole d. high gain 414.
77. It effectively cancels out the capacitance component of the antenna input impedance.
a. ground plane b. top hat c. loading coil d. shunt capacitance 415.
78. Indicate which of the following reasons for the use of an earth mat with antenna is false:
a. impossibility of a good ground conduction
b. provision of an earth for an antenna c. protection of personnel working
underneath
d. improvement of the radiation pattern of the antenna
416.
79. A metallic array that resembles a spoke wheel placed at the top of an antenna, it increases the shunt capacitance to ground reducing the overall antenna capacitance.
a. loading coil b. top loading c. series capacitance d. series inductors 417.
80. Indicate the antenna that is not wideband:
a. discone b. folded dipole c. helical d. marconi 418.
81. It is formed when two or more antenna
elements are combined to form a single antenna.
a. antenna elements b. antenna array c. driven elements d. parasitic elements 419.
82. One of the following is not a reason for the use of an antenna coupler:
a. to make the antenna look resistive b. to provide the output amplifier with
the correct load impedance c. to discriminate against harmonics d. to prevent reradiation of local
oscillators 420.
83. It is an individual radiator, such as a half or quarter-wave dipole.
a. antenna element b. antenna array c. reflector d. director 421.
84. Indicate which of the following reasons for using a counterpoise with antennas is false:
a. impossibility of a good ground connection
b. protection of personnel working underneath
c. provision of an earth for the antenna d. rockiness of the ground itself
422.
85. Type of antenna element that is directly connected to the transmission lines and receives from or is driven by the source.
a. driven array b. parasitic array c. driven element d. parasitic element 423.
86. Which of the following antennas is best excited from a waveguide?
a. biconical connected to the transmission lines.
a. parasitic array b. driven array c. parasitic array
d. parasitic element 425.
88. One of the following is very useful as a multi-band HF receiving antenna. This is the:
a. conical horn b. folded dipole c. log-periodic d. square loop 426.
89. A parasitic element that is longer than the driven element from which it receives energy.
a. driven element b. director
c. parasitic elements d. reflector
427.
90. One of the following consists of non-resonant antennas.
a. rhombic antenna b. folded-dipole antenna c. end-fire antenna d. broadside antenna 428.
91. A parasitic element that is shorter than its associated driven element.
a. redirector b. director c. reflector
d. parasitic element 429.
92. An ungrounded antenna near the ground.
a. acts as a single antenna near the ground
b. is unlikely to need an earth mat c. acts as an antenna array d. must be horizontally polarized 430.
93. It is a non-resonant antenna capable of operating satisfactorily over a relatively wide bandwidth, making it ideally suited for HF transmission.
a. turnstile antenna b. loop antenna c. rhombic antenna d. discone antenna 431.
94. A wide – bandwidth multi-element driven array is the ______.
a. end-fire b. log-periodic
c. yagi d. collinear 432.
95. It is a linear array antenna consisting of a dipole and two or more parasitic elements:
one reflector and one director.
a. broadside antenna b. end-fire antenna c. yagi-uda antenna d. phased array antenna 433.
96. An antenna which is consists of a cone that is truncated in a piece of circular waveguide.
a. pyramidal horn antenna b. circular horn antenna c. rectangular horn antenna d. circular horn antenna 434.
97. Which antenna has a unidirectional radiation pattern and gain?
a. dipole b. ground plane c. yagi
d. collinear 435.
98. An antenna formed by placing two dipoles at right angles to each other, 90 degrees out of phase.
a. discone antenna b. turnstile antenna c. bicone antenna
d. 5/8 wavelength antenna 436.
99. The radiation pattern of collinear and a broadside antenna is ________.
a. omnidirectional b. bidirectional c. unidirectional d. clover-leaf shaped
100. What is the bandwidth ration of log-periodic antenna? best antenna directivity?
a. 7 degrees b. 12 degrees c. 19 degrees
d. 28 degrees 438.
102. It is the ratio of the highest to the lowest frequency over which an antenna will satisfactorily operate.
a. channel ratio b. bandwidth ratio c. reflection ratio d. dynamic range 439.
103. An antenna has a power gain off 15.
The power applied to the antenna is 32 W.
The effective radiated power is ________.
a. 15 W b. 32 W c. 120 W d. 480 W 440.
104. It is simply a single-turn coil of wire that is significantly shorter than one wavelength and carries RF current.
a. turnstile antenna b. loop antenna c. rhombic antenna d. long-wire antenna 441.
105. A coax has an attenuation of 2.4 dB per 100 ft. The attenuation of 275 ft
a. 2.4 dB without having to physically move any of the individual antennas or antenna elements within the array.
a. end-fire array b. broadside antenna c. phased array antenna d. log-periodic antenna 443.
107. Conductors in multi-element antennas that do not receive energy directly from the transmission line are known as ______.
a. parasitic element b. driven element c. the boom
d. receptor 444.
108. It is a broadband VHF or UHF antenna that is suited for applications for which radiating circular rather than horizontal or vertical polarized electromagnetic waves are required.
a. discone antenna b. bicone antenna c. log-periodic antenna d. helical antenna 445.
109. Mode of propagation of helical antenna where electromagnetic radiation is in the direction at right angles to the axis of the helix.
a. normal mode b. axial mode c. helix mode d. helical mode 446.
110. Mode of propagation of helical antenna where the radiation of the antenna in the axial direction and produces a broadband relatively directional pattern.
a. helical mode b. normal mode c. axial mode d. helix mode 447.
111. In a Yagi antenna, maximum direction of radiation is toward the
a. director b. driven element c. reflector
a. side-to-back ratio b. front-to-side ratio c. back-to-side ratio d. front-to-back ratio 449.
113. The horizontal radiation pattern of a vertical dipole is a ____________.
a. figure of eight b. circle
c. narrow beam d. clover leaf
114. An antenna that provides extremely high gain and directivity and very popular for microwave radio and satellite communications link.
a. helical antenna b. parabolic antenna c. hyperbolic antenna d. log-periodic antenna 450.
115. Part of a parabolic antenna that houses the primary antenna which radiates electromagnetic waves toward the reflector.
a. feed mechanism b. focal point c. center feed d. feed antenna 451.
116. It is a passive device that simply reflects the energy radiated by the feed mechanism into a concentrated, highly directional emission in which the individual waves are all in phase with each other.
a. director
b. parabolic segment c. reflector
d. feed mechanism 452.
117. The energy near the edge of the parabolic dish that does not reflect but rather is diffracted around the edge of the dish.
a. spillover b. corona
c. dissipated power d. copper loss 453.
118. Determines the angular aperture of the reflector, which indirectly determines how much the primary radiation is reflected by the parabolic dish.
a. numerical aperture b. V number
c. aperture number d. aperture angle 454.
119. For a 2-m diameter parabolic reflector with 10W of power radiated by the feed mechanism operating at 6 GHz with a transmit antenna efficiency of 55%
and an aperture efficiency of 55%,
determine the beamwidth.
a. 1.25 degrees b. 2.25 degrees c. 1.5 degrees d. 1.75 degrees 455.
120. Type of feed mechanism where the primary radiating source is located just behind a small opening at the vertex of the paraboloid rather than at the focus.
a. cassegrain feed b. center feed c. horn feed d. antenna feed 456.
121. Discone radiation pattern is a. omnidirectional
b. unidirectional
123. An example of a marconi antenna is _______.
a. quarter wave vertical tower b. collinear
c. yagi d. rhombic 459.
124. At the ends of a half-wave antenna, what values of current and voltage exist compared to the remainder of the antenna?
a. minimum voltage and maximum current
b. minimum voltage and minimum current
c. equal voltage and current
d. maximum voltage and minimum current
460.
125. Radiation resistance is the ratio of ______.
a. radiated power to the antenna center current
b. radiated power to the square of the antenna center current
c. voltage to any point of the antenna d. square of voltage to the square of
current at any point in the antenna 461.
126. Consists of basic antenna connected to a transmission line plus one or more additional conductors
a. parasitic array b. directors
c. driven array d. reflectors
a. a phase monitor b. a frequency monitor c. an amplitude monitor d. a power monitor 464.
129. In antennas, which gives more forward gain?
a. reflector b. driven element c. parasitic element d. director
465.
130. Which of the following is longer?
a. director b. reflector c. driven element d. parasitic element 466.
131. Which is closer to the driven element?
a. parasitic element b. driven element c. director d. reflector 467.
132. How much do they differ in length from a half-wavelength?
a. 5%
b. 10%
c. 15%
d. 20%
468.
133. How much more feed-point impedance does a folded dipole have than a normal dipole?
a. two times as much b. three times as much c. four times as much d. five times as much 469.
134. How is it possible to produce 70-ohm twin lead?
a. by folding more parasitic element b. by manufacturing
c. by increasing the radiation resistance d. by increasing the length of the
antenna 470.
135. With similar size parabolic, plane reflector, and corner-reflector beams, which has greater gain?
a. plane reflector b. parabolic
c. corner-reflector beam d. V-beam
c. corner-reflector beam d. plane reflector
472.
137. Why would the wires of V-beam be closer together when used on higher frequencies?
a. main lobe lays farther to wire b. main lobe lays closer to wire c. secondary lobes closer to wire d. secondary lobes farther to wire 473.
138. How the V-beam is made unidirectional?
a. impedance terminated b. capacitive terminated c. inductive terminated d. resistor terminated 474.
139. Why might a rhombic be better than a V-beam?
a. it is resistor terminated b. more acreage needed
c. less acreage needed d. it is unidirectional 475.
140. Why is the usual rhombic not frequency – sensitive?
a. unidirectional
b. with its characteristic impedance c. less acreage required
d. main lobe is greater than back lobe 476.
141. In what direction is the null of small diameter loop in relation to the plane of the loop?
a. 45 degrees angle b. 180 degrees angle c. 360 degrees angle d. 90 degrees angle 477.
142. When is a loop unidirectional?
a. when horizontal b. when vertical c. when circular d. when unidirectional 478.
143. 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
479.
144. Why is pi-network superior to direct coupling to an antenna?
a. reduce harmonic radiation b. better frequency response c. better radiation of energy d. reduce power dissipation
a. reduce harmonic radiation b. better frequency response c. better radiation of energy d. reduce power dissipation