The fix, in short
Do a proper radio check. Use an automated radio-check service or a working channel, not channel 16, and compare with a handheld VHF on the same boat. If the handheld reaches farther, suspect the antenna system.
Inspect and clean every connector. Check the connectors at the radio, any splitter, the deck gland or mast-base joint, and the antenna. Clean or replace corroded connectors and seal outdoor joints against water.
Test the antenna and coax with an SWR meter. Fit an SWR meter or antenna analyzer between the radio and the cable. A healthy system reads low SWR, about 1.5:1 or better. A high reading points to a bad connector, wet or damaged coax, or a failed antenna.
Check any VHF/AIS splitter. If VHF and AIS share one antenna, test with the splitter bypassed. A faulty splitter can weaken both.
Replace wet coax or a damaged antenna. Wet or crushed coax can't be fixed by cleaning; replace it with good low-loss cable. A masthead antenna gives the best range.
Written by Sailor Cruiser crew. General guidance, not an inspection of your boat.
Equipment involved
- VHF: Fixed-mount VHF/DSC radio
- Antenna system: Masthead antenna, coax, connectors, optional VHF/AIS splitter
Related guides
- Guide: Your communications stack has no backup plan
- Guide: Electronics act haunted after heavy weather
- All ten public guides
Sources
Background reading we checked while writing this answer. The wording above is our own.
- Practical Sailor: How to prevent AIS and VHF antenna malfunction
- West Marine: How to check VHF antenna connections
- Practical Sailor: Testing VHF coaxial cable
Members get the full step-by-step for their boat — join
This page is the short version. Members ask about their own boat and gear, get a guided fix matched to their equipment, and keep every case on file.