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NMEA · Last updated November 2026

Commercial Marine Electronics Installer: free practice test

NMEA's non-manufacturer-specific installer certification for electronics on commercial vessels. The one-day class covers VHF and DSC, NMEA 0183, marine computers, Ethernet, Wi-Fi and USB, AIS, radar, satellite communications, heading sensors, coaxial cabling, sonar and BNWAS, followed by a 50-question open-book exam. There is no prerequisite, but NMEA expects basic knowledge of vessel types, marine electronics and ABYC DC electrical practice.

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About the NMEA Commercial Installer exam

NMEA's non-manufacturer-specific installer certification for electronics on commercial vessels. The one-day class covers VHF and DSC, NMEA 0183, marine computers, Ethernet, Wi-Fi and USB, AIS, radar, satellite communications, heading sensors, coaxial cabling, sonar and BNWAS, followed by a 50-question open-book exam. There is no prerequisite, but NMEA expects basic knowledge of vessel types, marine electronics and ABYC DC electrical practice.

What's on the exam

NMEA Commercial Installer
VHF Radio and DSC
8 key facts
AIS
7 key facts
Radar and Sonar
7 key facts
NMEA 0183 Data Interfacing
7 key facts
Networks, Marine Computers and Satellite Communications
7 key facts
Coaxial Cable and Connections
8 key facts
Heading Sensors and BNWAS
7 key facts

Each branch is a topic in the official outline. Members see every key fact on the full mind map. Read the free study guide →

How to pass the NMEA Commercial Installer exam

  • Open book is not the same as easy: 50 questions at the end of a long class leaves little time to search. Tab the NMEA 0400 sections on cabling, antennas and data connections before the exam starts.
  • You need 40 of 50. Questions on cable connections carry weight because NMEA calls them a common failure point; know connector sealing, bend radius and how to read a VSWR result.
  • Learn the NMEA 0183 rules cold: one talker per listener input, matching baud rates (4,800 vs 38,400) and how a sentence is built. Many interfacing faults come down to these three.
  • Commercial vessels add carriage rules that recreational installs don't have: Class A AIS, BNWAS alarm stages and heading inputs for AIS and radar. Expect questions on what each device needs from the others.

Save your results and get your Readiness Score

Create a free account after the test: your score by topic, a mistakes bank, the complete study notes for the first topic, flashcards and the ABYC Numbers & Formulas Sheet.

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What's in the premium NMEA Commercial Installer prep

Premium NMEA Commercial Installer prep is studied one topic at a time. Each step starts with that topic's key notes and flashcard deck, then its own question sets of 25, so you master one topic before you move to the next. When every topic is strong, the 6 full mock exams show you're ready.

3,000practice questions, every answer explained
6full-length mock exams, 50 questions each, timed
800flashcards with spaced repetition, sorted by topic
60comprehensive key notes across 7 topics

Your step-by-step study path

  1. 1
    VHF Radio and DSC9 key notes, 115 flashcards, then 450 practice questions in 18 sets of 25
    Notes free with an account
  2. 2
    AIS9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
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  3. 3
    Radar and Sonar9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
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  4. 4
    NMEA 0183 Data Interfacing9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
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  5. 5
    Networks, Marine Computers and Satellite Communications8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
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  6. 6
    Coaxial Cable and Connections8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25
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  7. 7
    Heading Sensors and BNWAS8 key notes, 110 flashcards, then 425 practice questions in 17 sets of 25
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  8. Final step: 6 full mock exams50 questions each, timed like test day. Pass them, then book your exam.
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Free with an account

Read the complete NMEA Commercial Installer study notes for “VHF Radio and DSC”

Our first full set of comprehensive notes, about 14 minutes of reading: Channels and power · DSC set-up · Antenna choice and placement · Power and commissioning, a worked exam example, the traps examiners use and a one-minute recap. Create a free account to read it and see how premium notes work before you decide.

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Study tools included

3,000 practice questions

3,000 exam-style questions per exam, organized topic by topic in sets of 25. Every answer explained, with the rule it comes from.

6 full mock exams

6 full-length timed mock exams per exam, with real question counts and time limits, so test day feels like practice day.

Exam Readiness Score

One 0 to 100 number that tells you when you're ready to book. Reach 80 and you're covered by our Pass Guarantee.

800 flashcards + spaced repetition

800 flashcards per exam, in a deck for each topic, that come back right before you'd forget them. Five minutes a day keeps every number fresh.

60 comprehensive key notes

60 key notes per exam, split across its topics and each explained in full: the concepts, worked exam examples, the traps examiners use and a quick recap. Your first set is free with an account.

Mind maps

See the whole exam on one screen: every topic and the facts under it.

Sample questions with answers

These are the questions in the free test above, with answers. Try the test first. You'll learn more by getting some wrong.

1. A newly installed VHF-DSC radio on a tug sends DSC calls, but a test alert shows no position. What is the most likely installation fault?
Answer: The GPS data output isn't connected to the radio's NMEA input. A DSC radio takes its position from a GPS feed (or manual entry); without that data it alerts with no position. A missing MMSI is tempting, but it would stop DSC calls altogether rather than just drop the position. Always connect and verify the GPS input at commissioning.
2. Two VHF antennas must share a short mast on a pilot boat. Which mounting arrangement gives the best isolation between them?
Answer: Stack one directly above the other with vertical separation. Vertical whip antennas radiate least along their own axis, so stacking one above the other places each in the other's null and gives far more isolation than the same horizontal spacing. Side-by-side mounting at small spacing couples strongly and desensitizes the receiver. Tilting an antenna wrecks its vertical polarization.
3. A tug's VHF antenna tip is 36 ft above the water. A coast station antenna is 100 ft high. Using radio-horizon distance in nautical miles of about 1.23 times the square root of each height in feet, what is the expected range?
Answer: About 20 nmi. Each station's radio horizon is 1.23 × √h: 1.23 × 6 = 7.4 nmi for the tug and 1.23 × 10 = 12.3 nmi for the coast station, and the two add to about 20 nmi. Using only one antenna's height gives 7 or 12 nmi. Antenna height, not transmitter power, sets VHF range.
4. Other vessels report that a supply boat's Class A AIS shows heading as 511 (not available) although its position is correct. What should the installer check first?
Answer: Whether the heading sensor's true-heading sentence reaches the AIS. Heading value 511 means the AIS has no heading input, so look at the heading sensor connection (for example an HDT sentence at the right baud rate). The internal GPS clearly works because the position is good. A Class A unit should be given heading from a compass, not from GPS course over ground.
5. A vessel is 30 m long with a 10 m beam. The GPS antenna for the AIS is 8 m from the bow and 3 m from the port side. What reference dimensions (A to bow, B to stern, C to port, D to starboard) should be entered?
Answer: A = 8, B = 22, C = 3, D = 7. A and B add to the length (8 + 22 = 30 m) and C and D add to the beam (3 + 7 = 10 m), measured from the antenna to the bow, stern, port and starboard. Swapping C and D shifts the vessel's outline on other ships' displays. Entering the full length or beam for one dimension is a common slip.
6. A stabilized satellite TV dome and a 4 kW open-array radar are going on the same arch. How should the radar be positioned?
Answer: Above or below the dome so the beam doesn't strike it. Radar energy hitting a satellite dome can overload or damage its low-noise block and causes interference, so the radar beam must clear the dome vertically. Mounting both at the same height puts the dome right in the main beam. A radar can't be set to face one way; the array rotates through 360 degrees.
7. A longliner needs reliable bottom tracking in 600 m of water. Which sounder transducer frequency suits this best?
Answer: A low frequency such as 38 to 50 kHz. Sound attenuates faster in water as frequency rises, so deep water needs low frequencies around 38 to 50 kHz, with a wider beam. 200 kHz gives finer detail and a narrow beam but loses the bottom long before 600 m. Choose the transducer frequency from the depth the vessel works in.
8. A radar has one NMEA 0183 input, but it needs both GPS position and heading from a separate compass. What is the correct way to connect them?
Answer: Feed both talkers into an NMEA 0183 multiplexer and its output to the radar. NMEA 0183 allows only one talker on each listener input; two outputs wired together corrupt each other's data. A multiplexer merges the sentences into one stream. A device's output pair can't receive data, and a GPS doesn't pass through what arrives at its input unless it is designed to.
9. An AIS receiver's NMEA 0183 output is wired to a chart plotter port that reads GPS data fine. No AIS targets appear and the port shows garbled characters. What is the likely fix?
Answer: Set the plotter port to 38,400 baud to match the AIS output. AIS data is sent at the high-speed rate of 38,400 baud, while most other NMEA 0183 devices use 4,800. A baud mismatch shows up as garbage or nothing. Reversed polarity would also stop data, but the first check for AIS is that the listener runs at 38,400.
10. A camera in the engine room must connect to the wheelhouse network switch. The Cat 6 cable route is 120 m long. What should the installer do?
Answer: Add a switch or fiber link so no copper run exceeds 100 m. Twisted-pair Ethernet is specified for 100 m per channel regardless of category or shielding, so a 120 m run needs an active device or fiber in between. Shielding helps with noise but doesn't extend the limit. Power over Ethernet adds power, not range.
11. On a supply vessel, the GPS loses its fix whenever the Iridium terminal transmits. Both antennas sit close together on the same rail. What is the best fix?
Answer: Move the GPS antenna well away from, and below, the Iridium antenna. Iridium transmits in the L-band close to the GPS L1 frequency (1575.42 MHz), so a nearby transmit antenna can overload a GPS receiver. Separating the antennas, with the GPS below the satellite antenna's pattern, is the cure. Longer coax only adds loss, and grounding changes don't stop RF overload.
12. A 25 W VHF feeds its antenna through 30 m of coax rated at 6 dB loss per 100 m at 150 MHz. About how much power reaches the antenna?
Answer: About 16.5 W. Loss is 6 × 0.3 = 1.8 dB, and 1.8 dB is a power ratio of 10^(−0.18) ≈ 0.66, so about 25 × 0.66 = 16.5 W arrives. Treating 1.8 dB as 1.8% gives 23 W, and 3 dB would halve it to 12.5 W. Long VHF runs justify lower-loss cable.
13. A tug's VHF range drops and the VSWR reading rises during heavy rain, then recovers in dry weather. What is the most likely cause?
Answer: Water entering an unsealed masthead coax connector. Moisture getting into a connector or cable changes its impedance, so VSWR rises and range falls in wet weather. Seal outdoor connectors with self-amalgamating tape or adhesive-lined heat shrink and add a drip loop. Low power or antenna height wouldn't change with rain.
14. On a ship's BNWAS, the dormant period ends and the bridge visual indication and then the bridge audible alarm go off. Nobody resets the system. What happens next?
Answer: A second-stage alarm sounds where the backup officer or master is. Under IMO MSC.128(75), an unreset BNWAS escalates: visual on the bridge, then audible on the bridge, then a second-stage remote alarm to the backup officer and/or master, then a third stage to other crew. It never sends distress alerts or changes steering.
15. A fluxgate compass reads 090° magnetic. Deviation on this heading is 3° W and local variation is 10° E. What is the true heading?
Answer: 097°. Correct from compass to true by adding east and subtracting west: 090 − 3 (deviation W) = 087° magnetic, then 087 + 10 (variation E) = 097° true. Applying the signs the wrong way gives 083° or 103°. Heading sensors feeding AIS and radar must be swung and corrected so this error is removed.

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NMEA Commercial Installer exam FAQ

How many questions are on the NMEA Commercial Installer exam?

50 multiple-choice questions, with a time limit of taken at the end of the one-day class; nmea does not publish a time limit for the first attempt (the renewal test has a 1-hour limit). Format: open book multiple choice. registration includes printed course slides and an electronic copy of the nmea 0400 installation standard. certification lasts 3 years; renewal costs us$100 and uses a 50-question, 1-hour test.

What is the passing score for NMEA Commercial Installer?

80% or higher (40 of 50). One free proctored retake within 90 days; after that you repeat the class at a 50% discount.

How much does the NMEA Commercial Installer exam cost?

Class and exam: US$520 for NMEA members, US$1,040 for nonmembers. NMEA Trade membership (US$450) includes one free installer course. ABYC charges members less than nonmembers, so confirm current fees with ABYC before you book.

Which languages is the NMEA Commercial Installer exam offered in?

English (NMEA also runs some installer classes in Spanish; check the schedule for this course).

Where do I take the NMEA Commercial Installer exam?

Exam taken at the end of the NMEA Commercial Installer training day, in person or online according to the published NMEA training schedule.

Is this NMEA Commercial Installer practice test free?

Yes. The 15-question practice test on this page is free, with an explanation for every answer and no signup. A free account also unlocks the complete study notes for the first topic. The full NMEA Commercial Installer prep is Premium at $147 a month for this exam.

What's in the premium NMEA Commercial Installer prep?

3,000 practice questions organized topic by topic (VHF Radio and DSC: 450; AIS: 425; Radar and Sonar: 425; NMEA 0183 Data Interfacing: 425; Networks, Marine Computers and Satellite Communications: 425; Coaxial Cable and Connections: 425; Heading Sensors and BNWAS: 425), 6 full-length timed mock exams of 50 questions, 800 flashcards and 60 comprehensive key notes split across all 7 topics, plus a mistakes bank and the Readiness Score.

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Exam details are summarized from the official candidate information available in November 2026. ABYC changes formats and fees, so confirm with National Marine Electronics Association (NMEA) before you book. ABYCExamPrep is not affiliated with the American Boat & Yacht Council.

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