Installation, Maintenance & Repair
Subelement F
Section 48
Maintenance
A thick layer of rust and corrosion on the surface of the parabolic dish will have what effect?
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No noticeable effect.
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Scatter and absorption of RADAR waves.
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Correct AnswerDecrease in performance, especially for weak targets.
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Slightly out of focus PPI scope.
"A thick layer of rust and corrosion on the surface of the parabolic dish" will decrease the gain of the antenna, i.e. the antenna's performance, so Answer C. is the right answer.
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The echo box is used for:
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Testing the wavelength of the incoming echo signal.
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Correct AnswerTesting and tuning of the RADAR unit by providing artificial targets.
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Amplification of the echo signal.
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Detection of the echo pulses.
The Echo Box is used to generate artificial echoes, so Answer B. is the right one.
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What should be done to the interior surface of a waveguide in order to minimize signal loss?
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Fill it with nitrogen gas.
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Paint it with nonconductive paint to prevent rust.
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Correct AnswerKeep it as clean as possible.
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Fill it with a high-grade electrical oil.
Keeping a waveguide as clean as possible will minimize signal losses, so Answer C. is the right one.
Answer A. is wrong because air is already 78% nitrogen so not much of a difference there.
Answers B. and D. are wrong because the presence of any material inside the waveguide will lose part of the RF energy as heat.
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Which of the following is the most useful instrument for RADAR servicing?
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Correct AnswerOscilloscope.
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Frequency Counter.
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R. F. Wattmeter.
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Audio generator.
Pulses are an essential part of RADAR System operation.
Of the instruments listed by the question, the only one able to display the shape and measure the timing of a pulse is the Oscilloscope, thus Answer A. is the right answer.
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A non-magnetic screwdriver should always be used when replacing what component?
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TR tube.
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Mixer.
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Video amplifier.
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Correct AnswerMagnetron.
Hint: magnet is in both the question and answer.
Using a a ferromagnetic screwdriver can damage the Magnetron by permanently altering the magnetic field inside it, so Answer D. is the right one.
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What kind of display would indicate water in the waveguide?
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Spoking.
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Correct AnswerLarge circular rings near the center.
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Loss of range rings.
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Wider than normal targets.
Water drops inside the waveguide will reflect part of the transmitter's signal back to the receiver regardless of antenna position causing the display to draw "large circular rings near the center".
Answer B. is the right one.
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