MST MST Marine Electronics & Navigation Systems 2 — Questions and Answers
Question 1: When installing a chartplotter/MFD on a vessel, what is the most important consideration for placement?
- Visibility from the helm with minimal sun glare and within arm's reach of the operator (Correct answer)
- Mounting as high as possible for GPS reception
- Placing it next to the VHF radio for short cable runs
- Mounting in an enclosed cabinet to protect from weather
Correct answer: Visibility from the helm with minimal sun glare and within arm's reach of the operator
The chartplotter must be readable in direct sunlight and operable without the helmsman leaning away from the wheel, per safe navigation practice.
Question 2: What does a depth sounder's transducer actually measure to calculate water depth?
- The time for a sonar pulse to travel to the bottom and return, converted to depth using the speed of sound in water (Correct answer)
- The water pressure at the hull
- The electrical resistance of the water column
- The GPS altitude difference between surface and bottom
Correct answer: The time for a sonar pulse to travel to the bottom and return, converted to depth using the speed of sound in water
The transducer emits a high-frequency sound pulse and measures the time for the echo to return; depth = (time × speed of sound) ÷ 2.
Question 3: What is the correct way to terminate an NMEA 2000 backbone cable to prevent signal reflections?
- Install 120-ohm terminator caps at both ends of the backbone (Correct answer)
- Leave both ends of the backbone open
- Connect both ends of the backbone to a ground point
- Install a 50-ohm terminator at one end only
Correct answer: Install 120-ohm terminator caps at both ends of the backbone
NMEA 2000 CAN bus networks require 120-ohm terminators at each end of the backbone to match impedance and prevent data signal reflections.
Question 4: A marine GPS chartplotter shows a 'No GPS Signal' warning. After confirming the antenna is connected, what is the next diagnostic step?
- Check the antenna cable connection at the chartplotter and test with a known-good antenna (Correct answer)
- Replace the chartplotter display unit immediately
- Reset the vessel's main circuit breaker
- Update the chartplotter's chart cards
Correct answer: Check the antenna cable connection at the chartplotter and test with a known-good antenna
The antenna cable connection at the chartplotter head is a common failure point; swapping to a known-good antenna isolates whether the issue is the antenna or the chartplotter.
Question 5: What USCG-required channel must all recreational vessels monitor when operating in US waters?
- VHF Channel 16 (Correct answer)
- VHF Channel 22A
- VHF Channel 9
- VHF Channel 6
Correct answer: VHF Channel 16
VHF Channel 16 is the international distress, safety, and calling channel; all recreational vessels are required to monitor it while underway.
Question 6: A NMEA 0183 sentence that begins with '$GPRMC' contains what information?
- Recommended minimum specific GPS/transit data including time, position, speed, and course (Correct answer)
- Depth sounder readings
- Wind speed and direction
- Engine RPM and oil pressure data
Correct answer: Recommended minimum specific GPS/transit data including time, position, speed, and course
The GPRMC sentence is one of the most common NMEA 0183 sentences and contains position, speed over ground, course, date, and magnetic variation.
MST MST Marine Electronics & Navigation Systems 2
When installing a chartplotter/MFD on a vessel, what is the most important consideration for placement?