NMEA CMET Exam Study Guide (2026)
Everything the Certified Marine Electronics Technician (CMET) tests, topic by topic: what each section covers, the facts that come up most, and how to study it. Pair it with the free 15-question practice test.
The exam at a glance
| Questions | 150 multiple-choice questions drawn from a pool of nearly 500 shared with the NMET exam |
|---|---|
| Time | 2 hours |
| Passing score | 80% (120 of 150) |
| Format | Proctored multiple choice with a standard calculator allowed. NMEA states the identical NMET exam is closed book. Prerequisites: current AMEI and Advanced NMEA 2000 certificates, and for US applicants an FCC GROL with Ship Radar Endorsement (FCC Elements 1, 3 and 8). This prep covers the knowledge exam only, not the FCC element exams |
| Certifying body | National Marine Electronics Association (NMEA) |
| Test provider | Proctored by NMEA: online with NMEA staff, by mail to a library, learning center or college you nominate, at the NMEA Conference, or at the NMEA office in Severna Park, Maryland. Book at least 2 weeks ahead |
Mind map: the whole exam on one screen
Read the complete NMEA CMET study notes for “NMEA 0400 Installation and Power Distribution”
Our first full set of comprehensive notes, about 14 minutes of reading: Conductors and connections · Sizing conductors for voltage drop · Circuit protection and distribution · Interference and routing · Documentation and handover, 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.
1. NMEA 0400 Installation and Power Distribution
NMEA does not publish topic weights. The NMEA 0400 Installation Standard is the only study text NMEA names, and power distribution is one of the listed pool areas, so expect installation practice in every part of the exam.
Key facts
- NMEA 0400 sets installation practice for marine electronics and builds on ABYC E-11 for DC wiring: tinned, stranded marine-grade copper, proper crimped terminals and support against chafe and vibration.
- Electronics circuits are sized for a 3% voltage drop. Use CM = (10.75 × I × L) ÷ E with L as the round-trip length and E as the allowed drop in volts.
- Overcurrent protection protects the wire: place it close to the power source and size it for the conductor, then add any device fuse the manufacturer specifies.
- Keep data and antenna cables apart from AC, high-current DC and inverter output cables; cross at right angles where they must meet.
- Ground cable shields at one end only (NMEA 2000: at the power insertion point) to avoid ground loops.
- Seal deck and bulkhead penetrations, form drip loops and leave service loops so equipment can be removed without cutting cables.
- Document the installation: wiring diagram, settings, offsets and test results handed to the owner or captain.
Flashcards
Exam tip: When a question gives a load and a distance, double the distance before anything else. Most wrong answers come from the one-way length.
2. Electrical and RF Principles
Electrical and RF principles are separate pool areas and also make up much of FCC Element 3, which CMET candidates hold. Expect Ohm's law, decibels, VSWR, wavelength and coax behavior.
Key facts
- Ohm's law E = I × R and power P = E × I underpin load, fuse and drop calculations.
- Decibels: +3 dB doubles power, +10 dB is ten times, −3 dB halves it. Add antenna gain and subtract cable and connector losses to find ERP.
- VSWR = (1 + |Γ|) ÷ (1 − |Γ|), with Γ = (ZL − Z0) ÷ (ZL + Z0). A perfect match is 1:1; 2:1 or worse usually means a fault.
- Wavelength in meters = 300 ÷ frequency in MHz. A quarter-wave at 156.8 MHz is about 0.48 m before velocity factor.
- Marine VHF, SSB and AIS use 50-ohm coax; satellite TV and many video feeds use 75-ohm cable.
- Coax loss rises with frequency and length: thin RG-58 loses far more on a long VHF run than RG-213 or low-loss foam types.
- Water in coax or a corroded connector raises loss and VSWR; seal outdoor connectors.
Flashcards
Exam tip: Do dB problems by counting: every 3 dB doubles or halves, every 10 dB multiplies or divides by ten. It is faster than logarithms under time pressure.
3. NMEA 0183, NMEA 2000 and Ethernet
NMEA 0183, NMEA 2000 and Ethernet are three of the pool's named areas, and CMET candidates must already hold Advanced NMEA 2000. Expect wiring limits, sentence and PGN knowledge and network fault finding.
Key facts
- NMEA 0183: differential (RS-422 style) serial, one talker to several listeners, 4800 baud standard and 38,400 baud for high-speed data such as AIS.
- 0183 sentences start with $ (or ! for encapsulated AIS), carry a two-letter talker ID and three-letter formatter, end with *hh checksum, and are at most 82 characters.
- NMEA 2000: CAN bus at 250 kbit/s with a backbone terminated by 120-ohm resistors at each end; powered-off resistance between CAN_H and CAN_L should be about 60 ohms.
- NMEA 2000 limits: drop cables up to 6 m each, 78 m cumulative, backbone up to 200 m with mid or heavy cable (100 m light), 50 physical connections.
- Power: LEN 1 = 50 mA; power the backbone near the electrical center of the load; every device must see at least 9 V.
- Wire colors: red NET-S (+), black NET-C (−), white CAN_H, blue CAN_L, bare shield.
- Marine Ethernet follows normal rules: about 100 m per copper segment, Cat5e or better, unique IP addresses on the same subnet.
Flashcards
Exam tip: For network faults, think layer by layer: power (voltage at the device), physical (terminators, resistance), then configuration (instances, sources, baud).
Test yourself on these topics
Take the free 15-question NMEA CMET test, then save your results to unlock your Readiness Score and the mistakes bank.
4. Radar
Radar is a named pool area and also the subject of FCC Element 8, which every US CMET holds. Expect theory (pulse, beamwidth, horizon), controls and installation and safety.
Key facts
- Range resolution = c × pulse length ÷ 2, about 150 m per microsecond of pulse.
- Maximum unambiguous range = c ÷ (2 × PRF); a lower PRF allows longer ranges.
Flashcards
Exam tip: Radar formula questions reward knowing c = 300 m per microsecond. Halve it for the round trip and most range answers fall out.
5. GPS, Heading Sensors and Autopilots
GPS, heading devices and autopilots are named pool areas. Expect sensor placement, update rates, calibration and autopilot tuning faults.
Key facts
- GNSS antennas need a clear view of the sky, away from radar beams and satcom transmit antennas; SBAS (WAAS in the US) improves accuracy.
- Fluxgate sensors mount low near the center of pitch and roll, away from ferrous metal, speakers and current-carrying cables, then are calibrated by turning slow circles.
Flashcards
Exam tip: If a heading error comes and goes with a load, think cables and magnets; if it is steady on certain headings, think deviation.
6. VHF, DSC, AIS, SSB and FCC Rules
VHF, DSC, SSB and AIS are named pool areas and the exam includes FCC General Radio Operator material. Expect channels, frequencies, MMSI rules, installation faults and licensing.
Key facts
- Marine VHF: 25 W high, 1 W low; channel 16 (156.800 MHz) distress and calling; channel 70 (156.525 MHz) DSC only; channel 13 bridge-to-bridge at 1 W.
- DSC needs a programmed MMSI and a position input to send a distress alert with position.
Flashcards
Exam tip: The CMET is the only NMEA exam where FCC rules are a prerequisite. If a stem asks who may adjust a transmitter, it is testing the license, not the technique.
7. Satcom, Sat TV, Wi-Fi, MFDs and Computers
Sat comm, Sat TV, Wi-Fi, video displays, computers and MFDs are all named pool areas. Expect look angles, blockage, frequency bands and integration faults.
Key facts
- Geostationary satellites orbit about 35,786 km (22,236 miles) above the equator; elevation angle falls as latitude rises.
- Stabilized domes need a clear line of sight; masts, arches and radar beams cause blockage and interference.
Flashcards
Exam tip: Satcom questions often hide a geometry problem. Picture where the satellite sits in the sky from the boat's latitude before choosing a cause.
8. Transducers and Hydroacoustics
Transducers and hydroacoustics are a named pool area. Expect depth and speed-of-sound calculations, frequency choice and installation by hull type.
Key facts
- Depth = speed of sound × time ÷ 2; sound travels about 1,500 m/s in seawater and about 1,435 m/s in fresh water.
- Lower frequencies (such as 50 kHz) reach deeper with wider beams; higher frequencies (200 kHz and up) give narrower beams and finer detail.
Flashcards
Exam tip: In depth calculations, check whether the stem says seawater or fresh water and remember to halve the round-trip time.
How to pass
- 150 questions in 120 minutes is 48 seconds each. Bank the quick recall items (channel numbers, PGNs, cable limits) to leave time for dB, VSWR and wire-size calculations.
- 80% means you can miss only 30 questions. Breadth matters: the pool spans more than 20 subject areas, so don't skip satcom or hydroacoustics because you rarely install them.
- NMEA says the exam is built on experience. For troubleshooting stems, choose the step a careful technician would take first, usually measuring before replacing.
- Apply for the exam early: NMEA advises paying the application fee about six months ahead so you have time to work through the NMEA 0400 standard and radar material it sends.
Frequently asked questions
How long should I study for the NMEA CMET exam?
Most working candidates need 4 to 8 weeks at 45 to 60 minutes a day. Book your exam once your Readiness Score has stayed at 80 or higher for about a week.
Can I take the NMEA CMET exam online?
Yes. ABYC certification exams are taken with a proctor: online through a remote proctoring service, or for some certifications at the end of an ABYC class. Format: proctored multiple choice with a standard calculator allowed. nmea states the identical nmet exam is closed book. prerequisites: current amei and advanced nmea 2000 certificates, and for us applicants an fcc grol with ship radar endorsement (fcc elements 1, 3 and 8). this prep covers the knowledge exam only, not the fcc element exams. Ask the ABYC Education Department which reference materials are allowed.
What score do I need to pass the NMEA CMET exam?
80% (120 of 150). The exam has 150 multiple-choice questions drawn from a pool of nearly 500 shared with the nmet exam and a time limit of 2 hours.
What are the most tested topics?
The outline covers nmea 0400 installation and power distribution, electrical and rf principles, nmea 0183, nmea 2000 and ethernet, radar, gps, heading sensors and autopilots, vhf, dsc, ais, ssb and fcc rules, satcom, sat tv, wi-fi, mfds and computers, transducers and hydroacoustics. Use the free practice test to see which ones you need most.
The premium NMEA CMET study path
Premium NMEA CMET 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.
Your step-by-step study path
- 1NMEA 0400 Installation and Power Distribution8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Notes free with an account
- 2Electrical and RF Principles8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 3NMEA 0183, NMEA 2000 and Ethernet8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 4Radar8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 5GPS, Heading Sensors and Autopilots7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 6VHF, DSC, AIS, SSB and FCC Rules7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 7Satcom, Sat TV, Wi-Fi, MFDs and Computers7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 8Transducers and Hydroacoustics7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- Final step: 6 full mock exams150 questions each, timed like test day. Pass them, then book your exam.Premium
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- 800 flashcards + 60 key notes per exam, by topic, plus mind maps
- Spaced repetition + mistakes bank
- Readiness Score & detailed reports
- Video lessons as they release
- Content updates during your access
- 5 bonuses: numbers and formulas sheet, standards map, study planner and more
- Pass Guarantee: complete the prep, pass or 100% back
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Summarized from ABYC's official candidate information and the rules cited, checked November 2026. Confirm current requirements with National Marine Electronics Association (NMEA).