FCC Commercial Element 8 pool, section 48

Subelement F

Installation, Maintenance & Repair

Section 48

Maintenance

848F1

A thick layer of rust and corrosion on the surface of the parabolic dish will have what effect?

A.
No noticeable effect.
B.
Scatter and absorption of RADAR waves.
Correct Answer
C.
Decrease in performance, especially for weak targets.
D.
Slightly out of focus PPI scope.

848F1

"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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848F2

The echo box is used for:

A.
Testing the wavelength of the incoming echo signal.
Correct Answer
B.
Testing and tuning of the RADAR unit by providing artificial targets.
C.
Amplification of the echo signal.
D.
Detection of the echo pulses.

848F2

The Echo Box is used to generate artificial echoes, so Answer B. is the right one.

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848F3

What should be done to the interior surface of a waveguide in order to minimize signal loss?

A.
Fill it with nitrogen gas.
B.
Paint it with nonconductive paint to prevent rust.
Correct Answer
C.
Keep it as clean as possible.
D.
Fill it with a high-grade electrical oil.

848F3

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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848F4

Which of the following is the most useful instrument for RADAR servicing?

Correct Answer
A.
Oscilloscope.
B.
Frequency Counter.
C.
R. F. Wattmeter.
D.
Audio generator.

848F4

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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848F5

A non-magnetic screwdriver should always be used when replacing what component?

A.
TR tube.
B.
Mixer.
C.
Video amplifier.
Correct Answer
D.
Magnetron.

848F5

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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848F6

What kind of display would indicate water in the waveguide?

A.
Spoking.
Correct Answer
B.
Large circular rings near the center.
C.
Loss of range rings.
D.
Wider than normal targets.

848F6

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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