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Published byCandice Binns Modified over 9 years ago
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Chapter 9 Radio Maintenance MComm – Ch9 - 1
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Confidence Testing Preventive Maintenance Corrective Maintenance Summary Overview MComm – Ch9 - 2 >>
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On Air Testing Backup Systems Coax Adapter Confidence Testing MComm – Ch9 - 3 >>
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Receivers Listen on a hailing or working frequency checks receiver and antenna Transmitter Make test call on a working frequency checks transmitter, receiver and antenna HF or satellite email Send message to self checks your equipment and shore interface DSC radios Make test call using DSC to another DSC radio need to know their MMSI On-Air Testing MComm – Ch9 - 4 >>
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Backup Systems If radio is inoperative, use handheld radio Charge handheld radio every 3 months Periodically test handheld radio Backup or Emergency VHF Antenna If you suspect a bad antenna: Use backup antenna Isolates problem MComm – Ch9 - 5 >>
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Coax Adapter With coax TNC to SO-239 adapter Can use high fixed antenna with handheld Good for when radio fails, but not antenna MComm – Ch9 - 6 >>
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Cleaning Cables and Connections Batteries Corrosion Control Preventive Maintenance MComm – Ch9 - 7 >>
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Cleaning Use fresh water and damp cloth May add soap to water Then wring out cloth Do NOT spray water on: Coax fittings Cable connections Speakers Microphones MComm – Ch9 - 8 >>
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Once a quarter Inspect power cables and antenna coax for: cuts in outer cover flattened coax (should be round) sharp bends (coax should have 2 inch radius) Tighten connections Once a year Check connections inside power panel CAUTION – first turn battery main switch “Off” Cables and Connections MComm – Ch9 - 9 >>
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Cables & Connections - 2 Sailboats, every 5 years Check antenna and coax at top of mast spray connector with QD Electronic Cleaner put dielectric silicone compound inside of connector tape coax and connector with rubber mastic tape Powerboats, check every other year Every 10 years Replace coax MComm – Ch9 - 10 >>
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Batteries Every 3 months Recharge handheld batteries Once a year Replace all “flashlight” batteries Check dated batteries (EPIRB and SART) Have them replaced before expiration date may have to send unit to approved facility Lithium batteries are difficult to ship MComm – Ch9 - 11 >>
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Corrosion Control Once a year, check Power cables Coax connectors Microphone connections Battery terminals If corrosion is noticed or suspected Spray contacts inside of connectors with QD Electronic Cleaner Then reconnect and tighten MComm – Ch9 - 12 >>
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When an FCC License is Required Visual Checks DC Troubleshooting Coax and Connectors Other Corrective Maintenance MComm – Ch9 - 13 >>
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For transmitter adjustments or repairs Includes screwdriver adjustments PG for radios General Radiotelephone Operator license Radar endorsement and PG for radars No license required To install unit, antenna and cables To repair/replace cables and coax When FCC License Required MComm – Ch9 - 14 >>
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Visual Checks Circuit breaker and radio “ON”? Are controls (especially squelch) set correctly? Power cable properly connected? Blown fuse? On back of unit In hot wire near unit In wire near breaker Microphone connected? Coax properly connected? Antenna damaged? MComm – Ch9 - 15 >>
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DC Troubleshooting If radio is “dead” and fuse on radio is good Check power cable connection for corrosion Spray with QD Electronic Cleaner Reconnect power cable and test If radio is still “dead” Disconnect power cable & measure DC voltage Should be slightly over 12 VDC Defective radio if <12 VDC MComm – Ch9 - 16 >>
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DC Troubleshooting - 2 If no DC voltage at the end of power cable Check for blown fuse Check for loose wires inside power panel At circuit breaker At DC bus bar If wire connections good & have 12 VDC at CB Defective wiring power panel to radio MComm – Ch9 - 17 >>
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Coax and Connectors Check coax cable connector for corrosion Use electronic cleaner Reconnect and tighten Check antenna coax for damage Flattened? (should be round) Sharp bends? (should be 2” radius) Replace if damaged Waterproof coax connections Inside apply dielectric silicone compound Tape outside with rubber mastic tape MComm – Ch9 - 18 >>
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SWR Meter Used to test coax and antenna Place in series with antenna coax Voltage Standing Wave Ratio (VSWR) Checks for impedance mismatches Indicates defective coax, connectors, or antenna Output power Verifies output power of transmitter Can be used to measure attenuation in coax MComm – Ch9 - 19 >>
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VSWR Measurement Insert SWR meter in series with antenna coax Use short section of coax On an idle channel: SWR meter switch to FWD Key transmitter Adjust sensitivity to full scale reading Release PTT switch Set switch on SWR meter to REF Key transmitter Read VSWR Should be less than 2:1 3:1 indicates defective system MComm – Ch9 - 20 >>
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Power Measurement Insert SWR meter in series with antenna coax First next to transmitter, then next to antenna On an idle channel: SWR meter switch to FWD Adjust sensitivity to full scale reading Set switch on SWR meter to POWER Read output power At transmitter should be 25 watts Next to antenna should be approx 20 watts If over 3 dB loss between transmitter & antenna Either coax or RF connectors are defective MComm – Ch9 - 21 >>
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Defective Microphone? Press PTT switch, but TX does not work Receiver stays on May be defective mike or connection Transmitter “keys” but no modulation May be defective mike or connection Spray connectors w/ QD Electronic Cleaner Then reconnect microphone If it still does not work Try with known good mike If radio now works, mike was bad MComm – Ch9 - 22 >>
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Defective NMEA 0183 cable? Easy test Good if DSC radio is displaying GPS info If no GPS data displayed and GPS is working Probably have bad NMEA 0183 cable / wires Troubleshoot cable/wires like power cable Check for corrosion Use Electronics Cleaner Check for loose wire connection Tighten screw Check each wire for continuity MComm – Ch9 - 23 >>
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90% of problems are: No DC to radio Corroded connectors Visual checks will identify some problems Use a multimeter for voltage check No DC: check breakers/fuses/wiring Make sure batteries are charged on backup Preventative maintenance is good Test before you need it Summary MComm – Ch9 - 24 >>
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