SI TECHNICAL 2018 UNIT IV QUESTION BANK

Transcription

1 SI TECHNICAL 2018 UNIT IV QUESTION BANK 1. In what range of frequencies are most omnidirectional horizontally polarized antennas used? A. VHF, UHF B. VLF, LF C. SH, EHF D. MF, HF 2. If the current ratios of the two or more elements must be held 5% and the phase angle to 3 the antenna is called a A. end fire array B. critical phased array C. broadband array D. wideband array 3. Which is a non-resonant antenna? A. Rhombic antenna B. Folded dipole C. End-fire array D. Yagi-Uda antenna 4. Gain of a half-wave dipole antenna over isotropic. A db B db C. 1 db D. 0dB 5. What is the gain of the Hertzian dipole over isotropic antenna? A db B db C db D db 6. is the measurement of a unilateral antenna properties of directivity A. Phase angle B. Antenna gain C. Beamwidth D. Bandwidth 7. In testing transmitter to prevent interfering with other stations, which type of antenna must be used? A. Void antenna B. Dummy antenna C. Hertzian antenna D. Isotropic antenna 8. The best solution to fading is. A. space diversity B. frequency diversity C. polarization diversity D. wavelength diversity 1 Page

2 9. All elements in a beam antennas are in line A. collinear B. yagi C. broadside array D. log-periodic 10. Which does not use vertical polarization antenna? A. AM Broadcasting B. FM Broadcasting C. Mobile Communications D. Satellite Communications 11. is an antenna with a number of half-wave antenna on it. A. Antenna array B. Tower C. Omni-directional D. Rhombic 12. An antenna with very high gain and very narrow beamwidth. A. Helical antenna B. Discone antenna C. Horn antenna D. Parabolic dish antenna 13. What determines antenna polarization? A. The frequency of the radiated wave B. The direction of the radiated wave C. The direction of the magnetic field vector D. The direction of the electric field vector 14. is the horizontal pointing angle of an antenna A. Azimuth B. Angle of elevation C. Right angle D. Beamwidth 15. What is the radiation characteristic of a dipole antenna? A. Omnidirectional B. Bidirectional C. Unidirectional D. Hemispherical 16. What is the theoretical gain of a Hertzian dipole? A db B db C. 3 db D. 0 db 17. An antenna with unity gain A. Rhombic B. Half-wave dipole C. Isotropic D. Whip 18. How will you increase the gain of an antenna? A. By adding several antennas in parallel B. By focusing the radiated energy in one desired direction C. By making antenna rods thicker D. By making the antenna size larger 2 Page

3 19. An antenna which is one-tenth wavelength long A. Hertzian dipole B. Loop antenna C. Marconi antenna D. Elementary doublet 20. Which of the following improves antenna directivity? A. Driven element B. Reflector element C. Director element D. Parasitic element 21. The antenna radiates polarized waves when the transmitter antenna is horizontally installed. A. Vertically B. negatively C. horizontally D. circularly 22. A simple half-wavelength antenna radiates the strongest signal A. at 45 degrees to its axis B. parallel to its axis C. at right angles to its axis D. at 60 degrees to its axis 23. 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 24. 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 25. 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. 26. 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 3 Page

4 27. 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 28. What is the electrical wavelength of a 500 MHz signal? A. 60 centimeters B. 6 meters C meter D. 60 meters 29. 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 30. What antenna radiates equally in all directions? A. Vertical antenna B. isotropic antenna C. Horizontal antenna D. Dipole antenna 31. Actual height of antenna should be at least A. one wavelength B. half wavelength C. quarter wavelength D. three-fourth wavelength 32. 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 33. The directivity pattern of an isotropic radiator is A. a figure-8 B. a sphere C. a unidirectional cardioid D. a parabola 34. 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 35. A theoretical reference antenna that provides a comparison for antenna measurements. A. Marconi antenna B. Isotropic radiator C. Yagi-Uda array D. Whip antenna 4 Page

5 36. 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 37. 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 38. 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 39. 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 40. To electrically increase 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 41. 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 42. 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 43. 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 5 Page

6 44. A directional antenna with two or more elements is known as a. folded dipole b. ground plane c. loop d. array 45. 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 46. What do the high pass filters generally comprise of? A. Capacitive series arm B. Capacitive shunt arm C. Inductive series arm D. Inductive shunt arm a. A & D b. A & C c. B & C d. B & D 47. which type of filter has stop band between two frequencies and passband in remaining frequencies? a. Low pass filter b. High pass filter c. Band pass filter d. Band elimination filter 48. A network either T or π, is said to be of the constant-k type if Z 1 and Z 2 of the network satisfy the relation? a) Z 1 Z 2 = k b) Z 1 Z 2 = k 2 c) Z 1 Z 2 = k 3 d) Z 1 Z 2 = k The cut-off frequency of the constant k-low pass filter is? a) 1/ LC b) 1/(π LC) c) LC d) π LC 50. The value of α in the pass band of constant k-low pass filter is? a) π b) π/4 c) π/2 d) A constant k low pass filter has fc = 500 Hz. At f = 1000 Hz, the attenuation is A. zero B. infinity C. may be zero or infinity D. more than zero but less than infinity 52. In any linear network, the elements like inductor, resistor and capacitor always a. Exhibit changes due to change in temperature b. Exhibit changes due to change in voltage c. Exhibit changes due to change in time d. Remains constant irrespective of change in temperature, voltage and time 6 Page

7 53. Which type of networks allow the physical separability of the network elements (resistors, inductors & capacitors) for analysis purpose? a. Lumped Networks b. Distributed Networks c. Unilateral Networks d. Bilateral Networks 54. Which type of impedance in asymmetrical network is estimated at a single pair of network terminals especially in the chain of infinite networks? a. Image impedance b. Iterative impedance c. Characteristic impedance d. All of the above 55. Where do the correctly terminated asymmetrical networks show termination at both the ports of network? a. In image impedances b. In iterative impedances c. In characteristic impedances d. All of the above 56. Which unit is used for the measurement of an insertion loss? a. Neper b. Weber c. Ohm d. Watt 57. While designing a constant-k low pass filter (T-section) shown below, what would be the value of capacitor if L/2 = 20mH, R 0 = 500 Ω and f c = 5 khz? a μf b μf c μf d μf 58. Which type of attenuators provide a fixed amount of attenuation by allowing the user to vary the attenuation in multiple steps? a. Ladder attenuators b. Variable-value attenuators c. Pad attenuators d. All of the above 59. Why are the variable attenuators applicable for radio broadcasting purposes? a. For speed control b. For volume control c. For time control d. For power control 60. What does the value of constant k represent? A. System gain factor B. Scale factor C. Vector factor D. System quality factor a. A & B b. C & D c. A & C d. B & D 7 Page

8 61. A special type of transmission line that consist of conducting metallic tube through which high frequency electromagnetic energy is propagated a. medium b. microstrip c. stripline d. waveguide 62. 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 63. 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 64. The horizontal radiation pattern of a dipole is a a. circle b. figure of eight c. clover leaf d. narrow beam 65. The size of antenna is inversely proportional to. a. frequency b. power c. radiation resistance d. wavelength 66. It is the ratio of the radiated to the reflected energy a. Radiation resistance b. Radiation efficiency c. Radiation constant d. Radiation antenna 67. The feed mechanism in a parabolic antenna that radiates the electromagnetic energy. a. Primary antenna b. Reflectors c. Secondary antenna d. Focal point 68. The radiation pattern plotted in terms of electric field strength or power density a. absolute radiation pattern b. relative radiation pattern c. absolute front lobe pattern d. absolute side lobe pattern 69. 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 70. Lobes adjacent to the front lobe a. Diagonal lobes b. Side lobes c. Front lobes d. Back lobes 8 Page

9 71. Lobes in a direction exactly opposite of the front lobe a. Side lobes b. Adjacent lobes c. Front lobes d. Back lobes 72. The line bisecting the major lobe, or 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 73. Refers to a field pattern that is close to the antenna. a. Induction field b. Far field c. Radiation field d. Capture field 74. It is the resistance that, if it replaced the antenna, would dissipate exactly the same amount of power that the antenna radiates. a. Directive gain b. Antenna efficiency c. Radiation resistance d. Antenna resistance 75. 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 beam width 76. 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 77. An antenna that transmits or receives equally well in all directions in one plane is said to be. a. omnidirectional b. bidirectional c. unidirectional d. quasi-directional 78. 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 79. The magnetic field of an antenna is perpendicular to the earth. The antenna s polarization. a. is vertical b. is horizontal c. is circular d. cannot be determined from the information given 9 Page

10 80. 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 81. 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 82. 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 83. 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 84. 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 85. 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 86. 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 87. 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 10 Page

11 88. In a Yagi antenna, maximum direction of radiation is toward the a. director b. driven element c. reflector d. sky 89. It is defined as the ratio of the antennas maximum gain in the forward direction to its maximum gain in its backward direction a. side-to-back ratio b. front-to-side ratio c. back-to-side ratio d. front-to-back ratio 90. The horizontal radiation pattern of a vertical dipole is a. a. figure of eight b. circle c. narrow beam d. clover leaf 91. 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 92. 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 93. 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 94. 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 95. 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 96. An example of a marconi antenna is. a. quarter wave vertical tower b. collinear c. yagi d. rhombic 11 Page

12 97. 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 98. 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 99. Which of the following is not a driven array? a. yagi b. broadside c. collinear d. end fire 100. What is used to determine phase difference between two broadcast antennas? a. a phase monitor b. a frequency monitor c. an amplitude monitor d. a power monitor 101. In Yagi antennas, which gives more forward gain? a. reflector b. driven element c. parasitic element d. director 102. Which of the following is longer in antennas? a. director b. reflector c. driven element d. parasitic element 103. Which is closer to the driven element? a. parasitic element b. driven element c. director d. reflector 104. In Yagi, how much do other elements differ in length from a halfwavelength? a. 5% b. 10% c. 15% d. 20% 105. 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 12 Page

13 106. With similar size, which has the narrowest lobes? a. parabolic b. V-beam c. corner-reflector beam d. plane reflector 107. When is a loop unidirectional? a. when horizontal b. when vertical c. when circular d. when unidirectional 108. Why are antenna ammeters often shorted out or disconnected from the antenna except when readings are desired? a. to replace it with dummy b. not to interface with transmission c. for proper reception of signals d. to protect from lightning 109. In what unit is field intensity measured? a. volts b. amperes c. watts/m d. mv/m 110. One of the following is very useful as a multiband HF receiving antenna. This is the: a. Conical horn b. Folded dipole c. Log-periodic d. Square loop 111. Which of the following antennas is best excited from a waveguide? a. Biconical b. Horn c. Helical d. Discone 112. Show 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 113. An antenna that is circularly polarized is the a. Helical b. Small circular loop c. Parabolic reflector d. Yagi-Uda 114. The standard reference antenna for the directive gain is the a. Infinitesimal dipole b. Isotropic antenna c. Elementary doublet d. Half-wave dipole 115. Cassegrain feed is used with a parabolic reflector to a. Increase the gain of the system b. Increase the beamwidth of the system c. Reduce the size of the main reflector d. Allow the feed to be places at a convenient point 13 Page

14 116. A helical antenna is used for satellite tracking because of its a. Circular polarization b. Manoeuvrability c. Broad bandwidth d. Good front-to-back ratio 117. One of the following is not omnidirectional antenna a. Half-wave dipole b. Log-periodic c. Discone d. Marconi 118. What do you call the energy that was not radiated into space or completely transmitted? a. Incident waves b. Captured waves c. Standing waves d. Modulated waves 119. The minimum number of turns a helix antenna must have a. 4 b. 5 c. 3 d Harmonic suppressor connected to an antenna a. Tank circuit b. M-derived filter c. Low-pass filter d. High-pass filter 121. A convenient method of determining antenna impedance a. Reactance circle b. Stub matching c. Smith chart d. Trial and error 122. EIRP stands for. a. Effective isotropic reflected power b. Effective isotropic refracted power c. Efficient and ideal radiated power d. Effective isotropic radiated power 123. A region in front of a parabolic antenna a. Transmission zone b. Fraunhofer c. Fresnel d. All of these 124. The reflector and director of an antenna array are considered as: a. Transcendental elements b. Feed-points c. Driven elements d. Parasitic elements 125. An electronic equipment used to measure standing wave ratio: a. Altimeter b. Multimeter c. Reflectometer d. Wavemeter 14 Page

15 126. What makes an antenna physically long electronically short? a. Adding C in series b. Top loading c. Adding L in series d. All of these 127. What is meant by antenna gain? a. The ratio of the signal in the forward direction to the signal in the backward direction b. The ratio of the amount of power produced by the antenna compared to the output power of the transmitter c. The final amplifier gain minus the transmission line losses (including any phasing lines present) d. The numeric ratio relating the radiated signal strength of an antenna to that of another antenna 128. It consists of a number of dipoles of equal size, equally spaces along a straight line with all dipoles fed in the same phase from the same source. a. End-fire array b. Yagi antenna c. Log-periodic antenna d. Broadside array 129. A type of array antenna which consists of one half-wave driven dipole, one reflector and one director. a. Log periodic dipole array b. Yagi-uda c. Herztian dipole d. Broadside collinear 130. It is measure of the microwave power radiated from an antenna as a function of angular direction from the antenna axis. a. Polarization b. Sidelobes c. Beamwidth d. Antenna pattern 131. Where does the maximum current and minimum voltage value on a resonant Hertz dipole exist? a. Center of the antenna b. Ends of the antenna c. Near the center of the antenna d. Near the end of the antenna 132. Where does the voltage node of a half-wave antenna exist? a. At feed point b. Near the feed point c. Near the center d. At center 133. This is a flexible vertical rod antenna commonly used on mobiles. a. Hertz b. Ground plane c. Whip d. Marconi 15 Page

16 134. One of the following prevents a transmitter from emitting a signal that interferes with other station on frequency during the test. a. Use of shielded antenna radiator b. Use of low height antenna c. Use of dummy antenna d. Use of grounded antenna 135. In high frequency radio transmission, the lower the radio frequency the of the antenna. a. Longer the length b. Bigger the diameter c. Shorter length d. Smaller the diameter 16 Page

17 SI TECHNICAL 2018 UNIT IV QUESTION BANK A B A A C C B A A B A D D A B A C B D D C C B D C D D A A B C A B D B C D C D A B A C D A A D B B D D D A B A A C A B A D C A B A B A A B B D A A C C A A B B B A C B A D A C A D B B A C A C A D B A A D B C A B A A D D C B D A B D A B C C C C D C D C A D D B C A A C D A 17 Page