Antenna Engineer Exam Questions

Key points of knowledge review questions for antenna technicians and senior technicians 1. Multiple choice questions 1. my country’s radio and television bands (frequency bands) are divided. The frequency range of medium wave is ( ), which is mainly used for domestic sound broadcasting. . 2. my country’s radio and television bands (frequency bands) are divided. The frequency range of very high frequency (meter wave) is ( ), represented by VHF. It is divided into three bands: I, II and III. Among them, the I band is used for terrestrial television. Channels 1 to 5 of broadcasting; band II is used for sound FM broadcasting; band III is used for channels 6 to 12 of terrestrial television broadcasting. 3. ( ) Due to the higher frequency, the ground absorbs it more strongly, so it can only propagate for tens of kilometers in the ground wave propagation mode, and is mainly propagated by sky waves. 4. The height of the medium-wave antenna has a very obvious impact on the pattern. When the antenna height is ( ), the main lobe is relatively narrow and has no side lobes. 5. The height of the medium-wave antenna has a very obvious impact on the pattern. When the antenna height ( ) is exceeded, side lobes will appear. 6. The height of the medium wave antenna has a very obvious impact on the pattern. When the antenna height is ( ), the main lobe is very narrow and the side lobe is very small. Therefore, in engineering, it is called the anti-fading height. 7. ( ) Tower antennas are generally composed of tower sections with an equilateral triangle cross-section. The side width W of each tower section is generally 500, 800, 1,000, 1,500mm, etc. The length of a standard tower section is 4m. and 4.5m, adjacent tower sections are connected with flanges, and tower sections generally adopt round steel structures. 8. The side width of the antenna tower section of a uniform cross-section tower can generally be 1/50 to 1/125 of the tower height. 9. The guy wire is connected to the ground anchor on the ground, and the angle between the guy wire and the ground should usually not exceed ( ). 10. Galvanized steel wire rope is used as the pull wire, and several insulators are installed on it to ensure that the length of each pull wire is far ( ) from the working wavelength. 11. For medium wave antennas, in order to improve the efficiency of the tower antenna and reduce the antenna's ( ), a ground network must be laid at the bottom of the tower antenna. 12. The ground network usually consists of several radial wires. The diameter of the radial wire is about 3mm and the length is 0.5l. The wires that make up the ground network usually do not exceed ( ). 13. The size of the base insulation is usually determined by the maximum voltage that an insulation height of 1 cm can withstand. 14. The drawstring insulators should be connected in parallel ( ) to provide a grounding path for static charges. 15. In order to protect against lightning, a ( ) can be connected between the feed point of the tower antenna and the ground grid, so for DC, the tower itself is grounded. 16. Four-tower antennas and eight-tower antennas can feed ( ) but ( ) currents to the transmitting oscillator, so that in addition to the main direction of emission, they can also transmit in the left and right directions in the horizontal plane. 17. The purpose of ( ) is to increase the effective height of the antenna. 18. The purpose of ( ) is to reduce the high-frequency current induced by the pull rope in a strong electromagnetic field to prevent the secondary radiation of the induced current from affecting the radiation pattern of the tower. 19. The function of ( ) is impedance matching, current phase shifting, power distribution, etc. 20. The function of ( ) is to match the input impedance of the tower with the characteristic impedance of the feeder. 21. The function of ( ) is to shift the main direction of antenna emission by an angle. 22. In addition to the feed network, a leakage coil should also be installed in the deployment room. Ground switches and ground hooks, as well as tower light transformers, etc. 23. The inductance of the leakage coil can be adjusted, and it is in a parallel resonance state with respect to the frequency of use, and with respect to the ground ( ). 24. Use copper shielding for high-power antennas above ( ). 25. Medium and short-wave feeders with operating wavelengths greater than 10 meters are mostly used ( ). 26. In order to avoid energy loss, TV and FM feeders working in the meter band adopt ( ). 27. Due to the skin effect of high frequencies, considerable power loss will also occur, causing a great attenuation of the transmitted high-frequency energy. Therefore, feeders working in the microwave band mostly use various types ( ). 28. Characteristic impedance of six-wire feeder ( ) ohm.

29. Since the ionosphere is unstable, in order to reduce fading, the half-power angle of the shortwave antenna should not be too small, usually above ( ). 30. ( ) is a symmetrical oscillator erected parallel to the ground. The difference between it and the symmetrical oscillator in free space lies in the influence of ground reflection. 31. ( ) is an antenna array composed of horizontally symmetrical oscillators. It is characterized by narrow main lobe, low side lobe level, high gain, and is mostly used for long-distance directional broadcasting in the shortwave band. 32. ( ) The ratio of the upper limit operating frequency to the lower limit operating frequency can be as high as 10 to 20, so one antenna can cover the entire shortwave broadcast band. 33. The input resistance of a horizontal half-wave antenna generally changes with the installation height in the range of 60 to 100Ω. Since the range of change is limited, the feed can be used ( ). 34. It is made by adding an aluminum tube or copper tube between the horizontal half-wave oscillator and the feeder ( ). 35. A stub usually refers to a short-circuit transmission line with a length ( ) of half a wavelength. 36. The vibrator of the fixed log-periodic antenna is made of copper-clad steel wire, and the characteristic impedance of the collective wire is mostly ( ). 37. The height of the center of the shortwave transmitting antenna feeder from the ground should not be ( ) 3.5 meters. 38. For the shortwave transmitting antenna feeder pole, the entire pole path should be as straight as possible. When it is necessary to turn, the angle should not be less than ( ). 39. The slot antenna is a short-wave long-distance directional transmitting antenna. 40. The purpose of the antenna reflection curtain is to enhance directional emission ( ). 41. ( ) refers to a section of transformation line from the main feeder to the branch feeder. 42. The pole-wrap antenna is also called the rotating field antenna. It is composed of an orthogonal bat-wing antenna fed with a 90° phase difference. It usually serves the ( ) band. 43. The ( ) of the antenna feeder system refers to the effective radiation energy rate of the antenna. 44. The propagation of ultrashort waves is based on the "direct-viewing distance" between the transmitter and receiver of the TV as its stable receiving range. The direct-viewing distance can be calculated according to ( ). 45. ( ) consists of two sets of mutually perpendicular wing-shaped oscillators. It has a wide frequency band and good horizontal directional roundness. It can be firmly fixed on the antenna mast without using insulators. 46. ??( ) consists of an antenna with a reflector. Usually installed on the side of the antenna tower, it has the characteristics of simple structure, convenient installation and flexibility. 47. ( ) Using traveling wave feed, the best radiation can be obtained when the length of each turn of the spiral is an integral multiple of the wavelength. The antenna has fewer feed points, a simple structure, a small windward surface, but a narrow frequency band. 48. ( ) is composed of a self-standing metal cylinder with longitudinal grooves arranged along the axis of the column. It has a simple structure, convenient power feeding, and small windward surface, so it is suitable for ceiling installation. However, the frequency band is narrow and it can generally only work on a single channel, so it is suitable for medium and small power radio stations. 49. In the VHF, UHF band and FM broadcast band antennas of TV broadcasts, ( ) consists of a reflector and a pair of thick dipoles to widen the operating frequency band. The diameter of the dipole is λ/30~λ/20, and the oscillator can also be made into a triangular cone-shaped oscillator. 50. In the VHF, UHF band and FM broadcast band antennas of TV broadcasts, ( ) uses two rings with a circumference of one wavelength to be installed on the reflection plate. It has fewer feed points, simple structure, and easy installation. Single board A higher gain can be obtained. To obtain a high gain, 4 rings or 6 rings can be connected in series. 51. In the VHF, UHF band and FM broadcast band antennas of television broadcasting, ( ) consists of wires or conductive strips installed on the reflecting plate. The length of each tooth of the guide belt is λ. It is characterized by a simple structure, the vertical component of the current is offset, and the radiation field is a horizontal wave. There are few feed points, and the single board can obtain high gain. 52. In the VHF, UHF band and FM broadcast band antennas of TV broadcasts, ( ) is composed of two orthogonal dipoles installed in a circular cavity, and is fed with a 90° phase difference to produce circularly polarized radiation. field. 53. Bat-wing antenna Two pairs of orthogonal practical antenna elements can form a rotating field antenna that is non-directional in the horizontal plane as long as the phase difference of the current flowing through them is ( ).

54. The number of layers of the antenna is mainly determined by the required ( ), usually six layers, three layers, four layers or eight layers. 55. The feeding method of the batwing antenna is cross-feeding to obtain ( ) phase difference, that is, one of the cables has the inner conductor connected to the vibrator, the outer conductor connected to the pillar, and the other cable has the inner conductor connected to the pillar. , the outer conductor is connected to the vibrator. 56. The feeding method of the batwing antenna is cross-feeding, and the electrical length of each branch cable must be accurately an integer multiple of ( ). 57. The more layers there are in the antenna, the greater the main lobe of the vertical directivity pattern is ( ), and the gain of the antenna is greater ( ). 58. For the relevant technical indicators of the four-dipole plate antenna, the input resistance ( ) is specified in the "Minutes of the Decimeter Wave TV Antenna System Technical Coordination Meeting" issued by the Ministry of Electronics and the Ministry of Radio and Television (85) Tongguang Zi No. 438. 59. If the TV broadcast uses ( ), ghost interference can be improved. 60. The speed ratio, also known as the wave contraction coefficient, is the ratio of the propagation speed or wavelength of the radio wave in the cable to the speed or wavelength of the radio wave propagating in free space. The ratio is ( ). 61. Gradually expand the wide side of an ordinary rectangular waveguide while keeping the narrow side unchanged, thus forming ( ). 62. The narrow side of an ordinary rectangular waveguide is gradually expanded while the wide side remains unchanged, thus forming ( ). 63. It is formed by expanding the wide side and narrow side of the rectangle at the same time ( ). 64. The electromagnetic wave propagating in ( ) is TE11 wave, which is the same as the main wave in the circular waveguide. 65. The ratio of the focal length f of the paraboloid of revolution to the oral surface d determines the shape of the paraboloid. ( ) is called a medium focal length paraboloid. 66. The ratio of the focal length f of the paraboloid of revolution to the surface d determines the shape of the paraboloid. ( ) is called a long focal length paraboloid. 67. The ratio of the focal length f of the paraboloid of revolution to the surface d determines the shape of the paraboloid. ( ) is called a short focal length paraboloid. 68. ( ) consists of a symmetrical oscillator plus a metal reflective disk with a diameter of about 0.8l. 69. ( ) evolved from ordinary speakers. It can receive both linearly polarized waves and circularly polarized waves, so it is suitable as a feed source for satellite receiving antennas. 70. ( ) is a high-efficiency feed, which consists of two circular waveguides nested together. 71. When maintaining the shortwave antenna, ( ) adjust the sag of the antenna curtain and the tension of the antenna element, and at the same time adjust the vertical curvature of the tower body and the pulling force of the cable. 72. When maintaining the shortwave antenna, ( ) go up to the tower and check the tightness of the tower structure and connecting bolts. 73. When maintaining short-wave antennas, perform general maintenance ( ) inspection of appearance. 74. When maintaining short-wave antennas, ( ) check the transmission part and joints of the field switch, and clean the insulators and contacts. 75. ( ) It may be that the antenna vibrator or lower lead is too loose, causing disconnection and virtual connection when swayed by strong wind. Most faults occur at the feed point. 76. ( ) If a local high potential appears on the lower lead, a section of copper wire of the same diameter can be tied to the ignition part to reduce the potential. Check the feeder line to find out the cause of the high potential. 77. ( ) The frequency is not suitable. Generally speaking, the frequency band of short-wave antennas is wider, and the reflection network is designed according to a certain fixed frequency. When the use frequency is significantly different from the design frequency, the reflection network is prone to ignition or even disconnection. The above faults can be solved by stringing ropes on the second tower and having people sit on the hanging basket. If the ignition and disconnection are severe, it may be recommended to change the frequency. 78. ( ) The feeder is too loose or has changed its geometric shape. The sag of the feeder should be adjusted in time to make the two feeders consistent. 79. The inspection of different types of TVs and FM antennas is different. ( ) Mainly check jumpers and ceramic plate capacitor contacts; contacts between feeders and vibrators or masts; clean insulators; fixation of vibrators and masts and slot widths changing circumstances. 80. The inspection of different types of TVs and FM antennas is different. ( ) Mainly check the fastening of the vibrator jumper; the fixation of the matching ring; cleaning of the insulator; the contacts and sealing of the sub-feeder and the vibrator, and the vibrator and the cavity and the fixation of the tower.

81. The inspection of different types of TVs and FM antennas is different. ( ) Mainly check the contacts between the sub-feeders and matching lines and the vibrator; the distance of the matching capacitor, the change of the vibrator position; the fixation of the vibrator to the bracket and tower, etc. 82. The inspection of different types of TVs and FM antennas is important. ( ) Mainly check the sealing of the vibrator; the fixation of the vibrator reflector and the tower, and the contacts between the vibrator and the sub-feeder. Layer spacing and offset dimensions of multilayer oscillators. 83. When maintaining TV and FM antennas, ( ) mainly check the power meter, reflectometer and air pressure gauge of the inflator under the tower and in the machine room, learn about the broadcast situation from the personnel on duty, and check the feeder parts and right-angle elbows Warm to touch. 84. When maintaining TV and FM antennas, ( ) mainly check the fixed points along the direction of the main feeder, the fixation of the rheostat (power divider), the contacts and fixation of the sub-feeders, the structure and fixation of the antenna vibrator, and deal with any problems found in time. 85. When maintaining TVs and FM antennas, ( ) mainly focus on the inflator system, clean the inflator and instrument cabinet, drain the inflator, check the molecular sieve or replace the desiccant, etc. 86. When maintaining TV and FM antennas, ( ), it is generally arranged in the dry season of April or November. Use a ground resistance rocker. One terminal is connected to the column shoe of the tower to ensure good contact. The other terminal is connected to a grounding drill 20 meters away and 40 meters away. Shake the rocker 120 times/min and adjust it. gear. 87. The measurement of ( ) can be carried out simultaneously with the measurement of the voltage standing wave ratio. The purpose of the measurement is to check whether the contact of each connection point in the system is good. 88. ( ) can be measured with a 1000 volt ohmmeter and shaken at the input end of the main feeder. If the antenna is open circuit, it can be measured directly. If the antenna is short circuit, the terminal of the main feeder needs to be open circuit. 89. Use a oscillator to measure ( ). One terminal is connected to the column shoe of the tower to ensure good contact. The other terminal is connected to the grounding rod 20 meters and 40 meters away respectively. Use 120 times/min to shake the oscillator. Shake the watch and adjust the gear. 90. ( ) is mainly caused by poor sealing means and poor materials. The solution can be to drill a water hole in the lower part of the vibrator and seal it with GSC butyl waterproof sealant. This kind of sealant has good insulation, high self-adhesiveness and can be disassembled. It is an ideal sealing material. 91. ( ) The reflection characteristics can be measured with a frequency sweeper. If the waveform is sparse, it can be considered that the reflection is at the near end. If the waveform is fine, the reflection point is near the antenna on the tower. If you use a network analyzer, you can directly measure the actual distance of the reflection point. If it is caused by contacts, you need to disassemble the connectors and reconnect them. In short, if the standing wave ratio deteriorates, you must find out the cause and repair it in time. 92. ( ) Mainly due to wind vibration, the gravity of the feeder itself, and poor fixing methods. Special clamps should be made to fix the sub-feeders on the rheostat and mast, and avoid stress on the contacts. 93. ( ) Angle steel and adjusting bolts can be used to make a fixed bridge. First fix the bridge on the tower or mast, and then fix the rheostat on the bridge with suitable clamps. The varistor in the low-power meter band is relatively slender and should be fixed on the shady side of the mast to avoid deformation caused by thermal expansion and contraction, which will affect the electrical indicators. 94. The ratio of the node voltage (or current) to the antinode voltage (or current) is called the feeder ( ). 95. The reciprocal of the traveling wave coefficient is that of the feeder ( ). 96. The antinodes (or wave nodes) of the two voltages (or currents) on the feeder are ( ) apart. 97. The distance between the antinode point of the voltage (or current) and the wave node of the voltage (or current) on the feeder is ( ). 98. When deploying short-wave antennas, the length used is related to the operating frequency. The electrical length can be calculated by ( ). 99. The steel tower mast is an open-air structure. During use, it is subject to seasonal changes, especially low temperature freezing and atmospheric corrosion. The load it bears is divided according to its nature. ( ) refers to the self-weight of the structure, the self-weight of the guy wire and the initial tension. The weight of the antenna and reflector net suspended from it.

100. The steel tower mast is an open-air structure. During use, it is subject to seasonal changes, especially low temperature freezing and atmospheric corrosion. The load it bears is divided according to its nature. ( ) refers to the force of wind and ice, Load etc. 101. The steel tower mast is an open-air structure. During use, it is subject to seasonal changes, especially low temperature freezing and atmospheric corrosion. The load it bears is divided according to its nature. ( ) refers to earthquakes, antenna curtain breakage, and cable insulation. Sudden unloading caused by damage, etc. 102. ( ) should start from the bottom up. Generally, visual inspection is used for appearance inspection, such as the anti-corrosion status of the tower body. If necessary, use a flat shovel and measuring tool to help judge. When the tower body is corroded in a large area and the corrosion depth reaches the main column or slope , 1/4 of the transverse web pole, you should consider updating the tower body. Check the welds of all joints and the connecting bolts of the flanges. If any problems are found, they should be repaired or updated.