Key Topic 90: RADAR Theory

Question 1

3-90O1: 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.
D. 500 to 2,000 pps.

Answer 1

D. 500 to 2,000 pps.

Question 2

3-90O2: 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.
C. 12.346 μs.
d. 1.073 μs.

Answer 2

C. 12.346 μs.

Question 3

3-90O3: What is the normal range of pulse widths?

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

Answer 3

B. .05 μs to 1.0 μs.

Question 4

3-90O4: Shipboard RADAR is most commonly operated in what band?

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

Answer 4

C. SHF.

Question 5

3-90O5: 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.
D. Pulse rate of the magnetron.

Answer 5

D. Pulse rate of the magnetron.

Question 6

3-90O6: If the elapsed time for a RADAR echo is 62 microseconds, what is the distance in nautical miles to the object?

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

Answer 6

A. 5 nautical miles.