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VHF Radio Tips & Troubleshooting

by Dave Alston

While less glamorous and expensive than most other boat electronics, the VHF radio can be critical to your safety and well being.  Having two units installed or at least a handheld backup is strongly recommended.  
Routine Checks:
It’s a good idea to verify the proper operation of your electronics prior to leaving the dock.  Weather channels can offer a quick check on your radio’s receiver and antenna.  Find a channel that normally comes in a little weak and scratchy and use that as your reference point.  Then go to a normal working frequency (i.e. 68) and transmit between your two units.  These quick tests don’t guarantee your unit is totally up to specifications but at least gives you verification of their basic operation.  Always turn your electronics off prior to starting your engines or changing generators to avoid exposing your electronics to voltage surges.
Transmit Problem:
There are several typical problems you can encounter with the transmit function of your VHF radio.  You may experience a complete transmitter failure, weak transmit, or loss of deviation (modulation/microphone).  
Antenna – Visually inspect your antenna, the coax cable, and the connection to your radio.
Voltage – Verify you are getting proper voltage (12 – 13.5 volts) to the radio.  Check switches, breakers, and fuses.  Try switching the radio to the low power mode and see if that helps.  Low voltage will cause more problems during the higher current draw of a 25 watt transmission than in the 1 watt mode.
Microphone – Bad connections inside the mic cable can cause loss of deviation/modulation (voice), or loss of PTT (Push-to-Talk) operation.  Most breaks occurs where the coil cord enters the radio or at the microphone itself.  A couple of wiggle and stretch tests may point to the problem area.
Receive Problem:
Receiver issues are generally weak reception, no reception, or no audio.
Antenna – Same as above.
Voltage – One sign of low voltage on some VHF radios is the inability to set the squelch properly.  If you’re unable to “quiet” the noise, it could be low voltage.
Speaker – If you experience no audio, it could mean a speaker failure.  The only way for you to test for this is to connect an external speaker.  Most radios have a small phono plug but others have a spare pair of wires in the power cable assembly.