CMRT Radar Performance Testing & Monitoring 1 — Questions and Answers
Question 1: What is the primary purpose of a performance monitor in a marine radar system?
- To measure antenna rotation speed
- To evaluate the overall sensitivity and transmitter power of the radar (Correct answer)
- To display target tracking data
- To control the automatic gain of the receiver
Correct answer: To evaluate the overall sensitivity and transmitter power of the radar
A radar performance monitor evaluates overall system sensitivity and transmitter power, giving the operator a continuous measure of the radar's operational condition.
Question 2: What primarily determines the minimum range of a marine radar?
- Transmitter peak power output
- Antenna gain and beamwidth
- Pulse width and receiver recovery time (Correct answer)
- Pulse repetition frequency
Correct answer: Pulse width and receiver recovery time
Minimum range is determined by the pulse width (duration of the transmitted burst) and the receiver recovery time needed after transmission ends before echoes can be detected.
Question 3: A peak power meter is used during radar maintenance to measure which parameter?
- Antenna rotation speed
- Receiver noise figure
- Magnetron pulse peak power output (Correct answer)
- Display brightness and contrast
Correct answer: Magnetron pulse peak power output
A peak power meter measures the instantaneous peak power of the magnetron's transmitted pulses, which is critical for assessing transmitter health and compliance with performance standards.
Question 4: What term describes the minimum signal level a radar receiver can detect above the noise floor?
- Pulse repetition interval
- Minimum discernible signal (MDS) (Correct answer)
- Intermediate frequency bandwidth
- Dynamic range
Correct answer: Minimum discernible signal (MDS)
Minimum discernible signal (MDS) is the lowest signal level detectable by the receiver above background noise, directly indicating receiver sensitivity.
Question 5: Which of the following best describes radar range resolution?
- The ability to determine the bearing of two closely spaced targets
- The ability to distinguish two targets at nearly the same range as separate echoes (Correct answer)
- The maximum detection range of the radar system
- The minimum radar cross-section detectable by the system
Correct answer: The ability to distinguish two targets at nearly the same range as separate echoes
Range resolution is the radar's ability to display two targets at nearly the same range as separate echoes, and is primarily determined by the transmitted pulse width.
Question 6: What effect does increasing the pulse repetition frequency (PRF) have on a marine radar?
- It increases maximum unambiguous detection range
- It improves range resolution significantly
- It reduces the maximum unambiguous range (Correct answer)
- It increases antenna gain
Correct answer: It reduces the maximum unambiguous range
A higher PRF means the radar transmits pulses more frequently, which reduces the maximum unambiguous range because echoes from distant targets may return after the next pulse is sent, causing range ambiguity.
Question 7: What is the typical duty cycle of a marine radar transmitter?
- 50 to 60 percent
- 0.1 to 2 percent (Correct answer)
- 25 to 30 percent
- 10 to 15 percent
Correct answer: 0.1 to 2 percent
Marine radar transmitters have very low duty cycles, typically between 0.1% and 2%, because the radar spends the vast majority of each cycle listening for returning echoes rather than transmitting.
CMRT Radar Performance Testing & Monitoring 1
What is the primary purpose of a performance monitor in a marine radar system?