Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/114

2-47. The elements of a broadside array are spaced one—half wavelength apart and are spaced how many wavelengths away from the reflector?

1. One—eighth
2. One—quarter
3. One—half
4. Three—quarter

2-48. What is the advantage, if any, to offsetting a feedhorn radiator for a parabolic dish?

1. A broader beam angle
2. The elimination of shadows
3. A narrower beam angle
4. No advantage

2-49. What is the range in nautical miles of the AN/GPN-27 radar?

1. 55
2. 75
3. 105
4. 155

2-50. What is the purpose of the jackscrew on the AS-3263/SPS-49(V) antenna?

1. To adjust the beam width
2. To vary the antenna feed horn focal distance
3. To adjust the beam elevation angle
4. To lockdown the antenna for PM

2-51. The OE-172/SPS-55 antenna normally operates in the linearly polarized mode, for what reason. would you use the circular polarized mode?

1. To compensate for the ships pitch and roll
2. To prevent jamming
3. To reduce return echoes from precipitation
4. To achieve over the horizon coverage

2-52. Which of the following is NOT a mode of operation. for the AN/SPN-35A radar set?

1. Final
2. Dual
3. Surveillance
4. Simultaneous

2-53. The two primary safety concerns associated with rf fields are rf burns and injuries caused by dielectric heating.

1. T
2. F

2-54. When a person. is standing in an rf field, power in excess of what level will cause a noticeable rise in body temperature?

1. 5 milliwatts
2. 10 milliwatts
3. 15 milliwatts
4. 20 milliwatts

2-55. When working aloft, what safety precaution(s) must be followed?

1. Tag out the antenna at the switchboard to prevent it from becoming operational
2. Secure motor safety switches for rotating antennas
3. Wear the proper oxygen breathing apparatus when working near a stack
4. All the above

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