CMRT Cheat Sheet 2026

The 30 highest-yield CMRT facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which type of antenna feed method for a parabolic dish results in feed blockage of the aperture? → Prime focus feed
2. Which waveguide mode is the dominant mode used in rectangular waveguides for marine radar feeds? → TE10
3. Per SOLAS requirements, how often must a ship's radar be tested for proper operation? → Before each voyage and during each navigational watch as appropriate
4. What is the FIRST step a CMRT professional should take before operating any equipment? → Conduct a pre-operation inspection and verify safety systems
5. What is the PRIMARY purpose of obtaining CMRT certification in Certified Marine Radar Technician? → To demonstrate verified competency and adherence to professional standards
6. Which NMEA sentence is most commonly used to feed GPS position data into a marine radar system? → NMEA $GPGLL or $GPRMC
7. What does radar stand for? → Radio Detection and Ranging.
8. What is the role of the heading sensor interface in a marine radar system? → Provides vessel heading to stabilize the radar picture and enable true bearing readout
9. A technician notices the radar antenna makes a grinding noise during rotation. After inspection, what is the FIRST component to check? → Pedestal bearing assembly
10. What does ARPA stand for in marine radar systems? → Automatic Radar Plotting Aid
11. Which IMO resolution sets the current performance standards for shipborne radar equipment? → MSC.192(79)
12. What is the role of radar reflectivity in detection? → It determines how easily the radar can detect the object.
13. What should be done if a radar system experiences signal loss? → Check antenna alignment and signal processing.
14. In FMCW radar used in some marine systems, the target range is determined by: → Measuring the frequency difference between transmitted and received signals
15. What is a 'blind sector' on a marine radar display? → An area of no radar coverage caused by an obstruction such as a mast or funnel
16. In marine radar, what does STC (Sensitivity Time Control) primarily compensate for? → Strong returns from nearby sea clutter
17. A radar shows strong target returns but all targets appear at double their actual range. What is the most likely cause? → Timebase generator is running at half the correct frequency
18. What phenomenon causes the radar horizon to extend slightly beyond the geometric horizon? → Tropospheric refraction bending the radar beam downward
19. What is the function of a modulator in a marine radar transmitter? → It generates the high-voltage pulse that triggers the magnetron to emit a microwave burst
20. A CMRT technician installs a replacement radar on a U.S.-flagged SOLAS vessel. Which document must be updated to reflect the new installation? → Ship's Safety Radio Certificate
21. Which preventive maintenance approach is MOST effective for CMRT professionals managing equipment? → Schedule regular maintenance based on manufacturer recommendations and usage patterns
22. What is the purpose of regular maintenance for radar systems? → To ensure optimal performance and longevity.
23. When installing multiple radar systems on a single vessel, what technique is used to prevent mutual interference between the two radars? → Staggering PRFs or using inter-pulse synchronization
24. Which parameter directly controls the range resolution of a pulsed radar? → Pulse width (pulse duration)
25. When replacing a waveguide section on a marine radar, what must be verified after reassembly to ensure proper operation? → VSWR (voltage standing wave ratio) is within specification
26. What is the VRM (Variable Range Marker) used for in radar navigation? → Measuring the range to a specific target or point of interest on the radar display
27. What ARPA alarm is triggered when a tracked target's CPA and TCPA fall within user-set threshold values? → Collision alarm (CPA/TCPA alarm)
28. A radar technician is using a substitution method to isolate a fault. This technique involves: → Replacing suspected faulty modules with known-good units to identify the defective stage
29. What is the function of the Electronic Bearing Line (EBL) on a radar display? → Measures the bearing to a target from own ship
30. How should radar cables be maintained? → By keeping cables free from damage and corrosion.