FCC Commercial Element 3 pool, section 90

Subelement O

RADAR

Section 90

RADAR Theory

390O1

What is the normal range of pulse repetition rates?

A.
2,000 to 4,000 pps.
B.
1,000 to 3,000 pps.
C.
500 to 1,000 pps.
Correct Answer
D.
500 to 2,000 pps.

390O1

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390O2

The RADAR range in nautical miles to an object can be found by measuring the elapsed time during a RADAR pulse and dividing this quantity by:

A.
0.87 seconds.
B.
1.15 µs.
Correct Answer
C.
12.346 µs.
D.
1.073 µs.

390O2

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390O3

What is the normal range of pulse widths?

A.
.05 μs to 0.1 μs.
Correct Answer
B.
.05 μs to 1.0 μs.
C.
1.0 μs to 3.5 μs.
D.
2.5 μs to 5.0 μs.

390O3

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390O4

Shipboard RADAR is most commonly operated in what band?

A.
VHF.
B.
UHF.
Correct Answer
C.
SHF.
D.
EHF.

390O4

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390O5

The pulse repetition rate (prr) of a RADAR refers to the:

A.
Reciprocal of the duty cycle.
B.
Pulse rate of the local oscillator.
C.
Pulse rate of the klystron.
Correct Answer
D.
Pulse rate of the magnetron.

390O5

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390O6

If the elapsed time for a RADAR echo is 62 microseconds, what is the distance in nautical miles to the object?

Correct Answer
A.
5 nautical miles.
B.
87 nautical miles.
C.
37 nautical miles.
D.
11.5 nautical miles.

390O6

Light travels 186,000 mps, or 161630 nmps. If the radar signal was returned in 62 microseconds, then the distance to the target was reached in half that time, or 31 microseconds. So, the distance to the target is

161630 nmps x 0.000031 secs = 5 nautical miles

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