MST MST Marine Electronics & Navigation Systems 1 — Questions and Answers
Question 1: What is the NMEA 2000 standard used for on modern marine vessels?
- A plug-and-play digital network protocol that allows marine electronics to share data on a common backbone (Correct answer)
- A radio communication frequency standard
- A GPS accuracy certification
- A safety standard for navigation lights
Correct answer: A plug-and-play digital network protocol that allows marine electronics to share data on a common backbone
NMEA 2000 is a CAN-bus-based networking standard that allows chartplotters, VHF radios, engines, depth finders, and other devices to share data seamlessly.
Question 2: What is the purpose of a marine VHF radio's DSC (Digital Selective Calling) feature?
- To transmit a digital distress alert with vessel identity and GPS position to the Coast Guard and nearby vessels (Correct answer)
- To receive weather forecasts automatically
- To communicate privately on a digital channel
- To track AIS targets on a chartplotter
Correct answer: To transmit a digital distress alert with vessel identity and GPS position to the Coast Guard and nearby vessels
DSC allows a single button press to broadcast a digital Mayday containing the vessel's MMSI number and GPS coordinates to rescue authorities.
Question 3: What minimum AWG wire size is generally required for a VHF marine radio installation drawing up to 6 amps?
- 18 AWG (with a 7-amp in-line fuse at the source) (Correct answer)
- 12 AWG
- 8 AWG
- 24 AWG
Correct answer: 18 AWG (with a 7-amp in-line fuse at the source)
ABYC E-11 specifies wire gauges based on current load and length; 18 AWG is acceptable for short runs under 7 amps with proper fusing.
Question 4: An AIS (Automatic Identification System) Class B transponder on a recreational vessel broadcasts what information?
- MMSI number, vessel name, position, speed, and course (Correct answer)
- Only the vessel's fuel level and engine hours
- Emergency-only signals — no routine broadcasts
- Only the vessel name — position is not transmitted
Correct answer: MMSI number, vessel name, position, speed, and course
AIS Class B transponders broadcast vessel identity, GPS position, speed over ground, course, and vessel type to nearby AIS-equipped vessels and VTS systems.
Question 5: What is the correct coaxial cable type for a VHF antenna installation to minimize signal loss on runs over 20 feet?
- RG-8X or RG-8U (low-loss coax) (Correct answer)
- RG-174 (mini coax)
- Standard RG-58
- Any antenna wire rated for outdoor use
Correct answer: RG-8X or RG-8U (low-loss coax)
Low-loss coaxial cable such as RG-8X significantly reduces signal attenuation over longer antenna cable runs compared to standard RG-58.
Question 6: What is the maximum distance at which two VHF radios at sea level can typically communicate using line-of-sight propagation?
- Approximately 20–25 nautical miles between two vessels depending on antenna height (Correct answer)
- 500 nautical miles
- 100 nautical miles reliably
- Unlimited range in calm conditions
Correct answer: Approximately 20–25 nautical miles between two vessels depending on antenna height
VHF radio is line-of-sight, and the range between vessels is limited by antenna height above the waterline — typically 20–25 nm vessel-to-vessel at normal antenna heights.
MST MST Marine Electronics & Navigation Systems 1
What is the NMEA 2000 standard used for on modern marine vessels?