Marine Electronics

Possible Causes

• •Water in coax connector
• •Damaged antenna element
• •Loose connector
• •Wrong antenna impedance

Diagnostic Steps

1. 1.Inspect all connectors for corrosion and water ingress
2. 2.Check coax for kinks or damage
3. 3.Measure SWR at radio and at antenna base to isolate fault
4. 4.Replace weatherproofing on all outdoor connections

Possible Causes

• •Failed preamp
• •Damaged antenna
• •Squelch set too high
• •Antenna disconnected

Diagnostic Steps

1. 1.Check squelch setting
2. 2.Verify antenna connection
3. 3.Try a known-good antenna
4. 4.Listen for background noise with antenna disconnected — you should hear static

Possible Causes

• •Mic gain too high
• •Defective microphone
• •TX audio clipping
• •Interference from nearby electronics

Diagnostic Steps

1. 1.Reduce microphone gain
2. 2.Test with a different microphone
3. 3.Record and play back your own transmission using a second radio
4. 4.Check for interference from inverters, alternators, or other electronics

Possible Causes

• •Blown fuse
• •Low supply voltage
• •Defective display backlight
• •Loose power connector

Diagnostic Steps

1. 1.Check inline fuse at radio and at power source
2. 2.Measure supply voltage at radio terminals — should be 12–14V
3. 3.Check for voltage drop under transmit load
4. 4.Inspect power connector crimps for corrosion

Possible Causes

• •MMSI not programmed
• •GPS not connected or no fix
• •DSC controller fault
• •Incorrect wiring to GPS

Diagnostic Steps

1. 1.Confirm MMSI is programmed into the radio
2. 2.Verify GPS is outputting NMEA sentences and radio display shows position
3. 3.Check NMEA cable wiring between GPS and radio
4. 4.Consult radio menu for DSC test function

Possible Causes

• •Open circuit in feedline
• •Failed PA transistor
• •Antenna tuner fault
• •Blown fuse

Diagnostic Steps

1. 1.Check all fuses and circuit breakers
2. 2.Verify antenna connection at tuner
3. 3.Bypass tuner and connect dummy load to test radio output
4. 4.Measure DC supply voltage at radio — HF radios draw 20–25A on transmit

Possible Causes

• •Open or shorted feedline to antenna
• •Antenna element grounded
• •Tuner fault
• •Feedline too short

Diagnostic Steps

1. 1.Check feedline from tuner to antenna for continuity
2. 2.Verify antenna is insulated from ground
3. 3.Manually cycle tuner through full range
4. 4.Verify GTO-15 high-voltage cable is used from tuner to backstay

Possible Causes

• •Engine alternator noise
• •Inverter interference
• •Poor grounding
• •Atmospheric interference on HF

Diagnostic Steps

1. 1.Listen with engine off to identify engine-related noise
2. 2.Check bonding between all metal through-hulls and ground bus
3. 3.Add ferrite cores to power leads near radio
4. 4.Try different HF bands — lower bands more affected at night

Possible Causes

• •Excessive voltage drop on transmit
• •Inadequate wiring gauge
• •Poor battery connection
• •Blown negative fuse

Diagnostic Steps

1. 1.Check negative fuse in addition to positive fuse
2. 2.Measure voltage at radio terminals while keying transmitter
3. 3.Upgrade wiring to minimum 8 AWG for HF radio power leads
4. 4.Inspect battery terminals for corrosion

Possible Causes

• •Antenna not rotating
• •Transmitter fault
• •Cable fault between antenna and display
• •Warm-up period not complete

Diagnostic Steps

1. 1.Listen for antenna rotation
2. 2.Allow full warm-up period (up to 3 minutes for magnetron radars)
3. 3.Check power cable to antenna unit
4. 4.Inspect coax or data cable between pedestal and display for damage

Possible Causes

• •Gain set too low
• •Sea clutter (STC) set too high
• •Rain clutter (FTC) set incorrectly
• •Magnetron near end of life

Diagnostic Steps

1. 1.Increase gain until background noise just visible
2. 2.Reduce STC (sea clutter) control
3. 3.Adjust FTC (rain clutter) setting
4. 4.Have magnetron output power tested

Possible Causes

• •Interference from another radar
• •Radar interference rejection not enabled
• •Electrical interference from other equipment

Diagnostic Steps

1. 1.Enable radar interference rejection (IR) mode on display
2. 2.Characteristic pattern is random dots or arcs — confirms radar-to-radar interference
3. 3.Check for electrical interference from engine room electronics

Possible Causes

• •Incorrect range scale selected
• •Display calibration drift
• •Software issue

Diagnostic Steps

1. 1.Verify correct range scale is selected
2. 2.Compare radar range to known landmark at measured distance
3. 3.Perform range calibration if available in service menu
4. 4.Update firmware if available

Possible Causes

• •Battery expired
• •Unit damaged
• •Self-test antenna fault
• •GPS module failure (406 MHz units)

Diagnostic Steps

1. 1.Check battery expiry date on label
2. 2.Inspect unit for physical damage or water ingress
3. 3.Ensure self-test is conducted per manufacturer procedure
4. 4.Contact manufacturer or authorized service if battery is current and test still fails

Possible Causes

• •Wrong station or message category selected for rejection
• •Frequency mismatch
• •Antenna fault
• •Printer paper jam or out of paper

Diagnostic Steps

1. 1.Check receiver settings — verify correct station IDs and message categories
2. 2.Confirm frequency is set to 518 kHz (international) or 490 kHz (national)
3. 3.Check antenna connection
4. 4.Verify printer paper is loaded correctly

Possible Causes

• •Antenna obstructed by mast or rigging
• •Satellite not in view at current latitude
• •Terminal not registered
• •Power supply issue

Diagnostic Steps

1. 1.Check antenna has clear view of sky
2. 2.Verify vessel is within coverage area (not above 76° latitude)
3. 3.Confirm terminal is registered with service provider
4. 4.Check power supply voltage to terminal

Possible Causes

• •MMSI not programmed
• •GPS not providing position fix
• •TX antenna fault
• •Unit in receive-only mode

Diagnostic Steps

1. 1.Verify MMSI is programmed — unit will not transmit without a valid MMSI
2. 2.Confirm GPS is connected and providing a valid position fix — AIS will not transmit without position data
3. 3.Check that unit is set to Class A or Class B transponder mode, not receive-only
4. 4.Verify TX antenna connection — AIS shares the VHF antenna via a splitter on most installations
5. 5.Check antenna splitter — a failed splitter passes receive but blocks transmit

Possible Causes

• •Antenna fault or splitter issue
• •RX antenna disconnected
• •Software filter excluding targets
• •No vessels in range transmitting AIS

Diagnostic Steps

1. 1.Check antenna and splitter connections
2. 2.Verify no display filters are excluding targets by vessel type, range, or heading
3. 3.Confirm nearby vessels are AIS-equipped — not all vessels carry AIS
4. 4.Check AIS receiver sensitivity by verifying shore-based AIS targets are visible in port

Possible Causes

• •GPS position error
• •GPS antenna obstruction
• •Wrong datum selected
• •HDOP too high

Diagnostic Steps

1. 1.Verify GPS antenna has clear sky view
2. 2.Check GPS HDOP value — should be below 2.0 for reliable AIS position
3. 3.Confirm datum is set to WGS84 in GPS settings
4. 4.Cross-check position against chartplotter GPS

Possible Causes

• •Antenna splitter fault
• •Splitter insertion loss too high
• •Incorrect splitter type for AIS frequencies
• •Shared antenna without splitter

Diagnostic Steps

1. 1.Verify a dedicated AIS/VHF antenna splitter is installed — do not share the antenna without one
2. 2.Check splitter insertion loss spec — should be less than 1 dB on both ports
3. 3.Inspect splitter for water ingress or corrosion
4. 4.Try a separate dedicated antenna for the AIS unit if interference persists

Possible Causes

• •Battery expired or low
• •Unit damaged from water ingress
• •Self-test antenna fault
• •Firmware issue

Diagnostic Steps

1. 1.Check battery expiry date on the label — batteries must be replaced every 5 years regardless of use
2. 2.Inspect housing for cracks or water ingress — even minor damage can prevent self-test
3. 3.Ensure self-test is performed exactly per manufacturer procedure — timing and button sequence vary by brand
4. 4.If battery is current and housing is intact, return to manufacturer or authorized service center

Possible Causes

• •Bracket float switch triggered by water
• •Unit knocked or dropped
• •Hydrostatic release activated prematurely
• •Battery connector dislodged during handling

Diagnostic Steps

1. 1.Switch off immediately using the designated OFF switch or procedure
2. 2.Contact the relevant MRCC (Maritime Rescue Coordination Center) immediately to cancel the alert — a false alert that is not cancelled triggers a full SAR response
3. 3.Inspect the float switch and bracket for damage or saltwater intrusion
4. 4.Document the incident — false alerts must be reported to the FCC

Possible Causes

• •Internal GPS has not acquired fix
• •Antenna obstructed
• •GPS module failure
• •Unit activated indoors or in enclosed space

Diagnostic Steps

1. 1.Allow 5–10 minutes for internal GPS to acquire satellites after activation — initial distress signal transmits on 406 MHz without GPS, position is added once fix is obtained
2. 2.Ensure EPIRB has clear view of sky — do not activate indoors
3. 3.If GPS never acquires after 15+ minutes outdoors, internal GPS module may have failed — replace unit

Possible Causes

• •Salt water exposure without rinsing
• •Age — releases have a limited service life
• •UV degradation of housing

Diagnostic Steps

1. 1.Inspect hydrostatic release annually — replace if corroded, cracked, or past service date
2. 2.Rinse bracket and release with fresh water after salt water exposure
3. 3.Check manufacturer's recommended replacement interval — typically 2 years for hydrostatic releases
4. 4.Never lubricate the hydrostatic release mechanism

Possible Causes

• •GPS antenna obstruction
• •Antenna cable fault
• •Cold start delay
• •Antenna failure

Diagnostic Steps

1. 1.Ensure GPS antenna has unobstructed 360-degree sky view — even partial obstruction by radar domes or masts significantly degrades reception
2. 2.Allow 5–10 minutes for cold start fix after extended power-off periods
3. 3.Check GPS antenna cable connections at both the antenna and chartplotter
4. 4.Verify antenna power — most active GPS antennas require 3.3–5V from the chartplotter, check cable for damage

Possible Causes

• •Multipath reflections from nearby structures
• •High HDOP
• •Electrical interference
• •Antenna mounting location

Diagnostic Steps

1. 1.Check HDOP value on chartplotter — values above 2.0 indicate poor satellite geometry
2. 2.Relocate antenna away from radar dome, metal masts, or superstructure that may cause multipath
3. 3.Check for electrical interference from inverters, radar, or VHF radio
4. 4.Compare position to known landmark or second GPS source to verify extent of drift

Possible Causes

• •Chart card not inserted or not recognized
• •Expired chart subscription
• •Wrong chart region installed
• •Corrupted chart data

Diagnostic Steps

1. 1.Remove and reinsert chart card — check for corrosion on contacts
2. 2.Verify chart subscription is current — most electronic chart providers require annual renewal
3. 3.Confirm correct region is selected in chartplotter settings
4. 4.Try a known-good chart card to isolate whether the issue is the card or the chartplotter

Possible Causes

• •Incorrect baud rate
• •Wiring fault on NMEA bus
• •Wrong NMEA sentences enabled
• •Ground loop on long cable runs

Diagnostic Steps

1. 1.Verify baud rate — NMEA 0183 default is 4800 baud, some instruments use 38400
2. 2.Check TX from GPS connects to RX on receiving instrument — a common wiring mistake
3. 3.Verify GGA, RMC, and VTG sentences are enabled in the GPS output settings
4. 4.For NMEA 2000 networks, check backbone termination — network requires exactly two 120-ohm terminators

Possible Causes

• •AIS not connected to chartplotter
• •NMEA sentence type mismatch
• •AIS unit in receive-only mode
• •Cable fault between AIS and chartplotter

Diagnostic Steps

1. 1.Verify AIS unit is connected to chartplotter via NMEA 0183 or NMEA 2000
2. 2.Confirm AIS is outputting VDM sentences (NMEA 0183) or PGN 129038/129039 (NMEA 2000)
3. 3.Check chartplotter AIS display settings — AIS overlay may be disabled in the layers menu
4. 4.Test connection by checking if chartplotter shows own vessel AIS data from the transponder