CMRT Installation & Maintenance Procedures 5 — Questions and Answers
Question 1: When tightening waveguide flange bolts during installation, the correct approach is to:
- Tighten fully one bolt at a time in sequence
- Tighten in a star (cross) pattern to even compression (Correct answer)
- Apply thread-locking compound and torque to maximum
- Hand-tighten only to avoid deforming the flange
Correct answer: Tighten in a star (cross) pattern to even compression
Cross-pattern tightening ensures even gasket compression across the flange face, preventing leaks and maintaining waveguide alignment and VSWR.
Question 2: A radar technician is testing the transmitter peak power using a directional coupler and power meter. The measured average power is 25 W with a PRF of 1000 Hz and a pulse width of 0.1 µs. What is the approximate peak power?
- 25 kW
- 250 kW (Correct answer)
- 2.5 kW
- 25 MW
Correct answer: 250 kW
Peak power = average power / duty cycle; duty cycle = 0.1 µs × 1000 Hz = 0.0001, so peak power = 25 W / 0.0001 = 250,000 W = 250 kW.
Question 3: During antenna scanner installation at height, the technician should use a safety harness rated to which standard for working at height on marine vessels?
- EN 361 or equivalent fall-arrest harness standard (Correct answer)
- ANSI/ISA-18.2 for alarm management
- ISO 9001 quality management
- NFPA 70E electrical safety only
Correct answer: EN 361 or equivalent fall-arrest harness standard
EN 361 (or equivalent national standard) governs full-body fall-arrest harnesses required for any work at height above 1.8 m on vessel masts.
Question 4: After installing a new radar system, the technician performs a racon (radar beacon) test. A racon response should appear on the display as:
- A bright dot at the vessel's own position
- A Morse-coded dash beginning just beyond the racon's true position (Correct answer)
- A solid circle at the racon's range
- A heading line extension toward the racon
Correct answer: A Morse-coded dash beginning just beyond the racon's true position
A racon transponder replies with a Morse-code dash that paints radially outward from just beyond the racon's true range to identify it on the radar display.
Question 5: When documenting a radar installation for vessel records, which items must be recorded as a minimum?
- Installer's personal opinion of equipment quality
- Equipment make/model/serial numbers, installation date, test results, and deviations from manufacturer specs (Correct answer)
- Only the invoice and purchase order
- Magnetron serial number and expiry date only
Correct answer: Equipment make/model/serial numbers, installation date, test results, and deviations from manufacturer specs
Proper installation records must include equipment identifiers, date, performance test results, and any noted deviations to support future maintenance and regulatory inspections.
Question 6: When a radar receiver's noise figure degrades significantly, the primary observable effect during sea trials will be:
- Increased antenna rotation speed
- Reduced detection range of small targets in calm conditions (Correct answer)
- Wider pulse width on the display
- Higher PRF on the modulator output
Correct answer: Reduced detection range of small targets in calm conditions
A degraded noise figure raises the minimum detectable signal threshold, reducing the receiver's sensitivity and shortening the range at which small targets are detected.
Question 7: To prevent galvanic corrosion between a stainless steel antenna mount and an aluminum mast, the technician should:
- Apply a bimetallic zinc compound paste and use isolating sleeves on fasteners (Correct answer)
- Weld the mount directly to the mast for best conductivity
- Use copper bolts for a tighter joint
- Leave the junction unpainted to allow natural oxidation sealing
Correct answer: Apply a bimetallic zinc compound paste and use isolating sleeves on fasteners
Isolating the dissimilar metals with a corrosion-inhibiting compound and non-conductive sleeves breaks the galvanic cell that would otherwise accelerate aluminum corrosion.
CMRT Installation & Maintenance Procedures 5
When tightening waveguide flange bolts during installation, the correct approach is to: