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