Describe the symptom precisely
“The VHF is not working” can describe several different problems. Transmission may be weak or non-existent. Reception may be noisy. One channel may work while another does not. The radio may reset, dim or turn off when transmitting.
Write down whether the problem is on transmit, receive or both, whether it changes with distance, and whether other radios can hear you. If you can hear others but they cannot hear you, the transmit side or antenna system is more likely to be involved.
Record when the problem started and whether anything changed around that time: a new antenna, a repaired mast, new electronics, a changed power supply or work near the radio installation.
- Transmit, receive, or both?
- Is the audio clear, weak, distorted or absent?
- Does it affect all channels or only some?
- Does the radio reset or dim when transmitting?
- Did it change after recent work or equipment changes?
Antenna and coaxial cable
The antenna and its coaxial cable are often the first place to look when transmit and receive performance both fall away. A damaged cable, water in a connector, a broken centre conductor or a poor shield connection can affect reception and transmission differently.
Antenna mounting matters as well. A masthead antenna has a different installation from a rail-mounted emergency antenna. The cable route, connector condition and the way the antenna is grounded or isolated all affect how the system performs.
Visible damage is not always present. A connector can look sound and still have a poor electrical connection, particularly where it has been exposed to salt water or repeated flexing.
Power and voltage during transmission
VHF radios draw a relatively high current when transmitting. If the supply voltage drops, the radio may reduce output, reset or switch off. That can look like a radio fault when the real problem is the power circuit.
Check whether the symptom is worse when the engine is off, when the batteries are low, or when other equipment is running. A radio that works at the berth but fails at anchor is often showing a supply problem rather than a radio problem.
Look at the connections behind the radio, the fuse or breaker supplying it, and whether the radio shares a circuit with other high-load equipment. A dedicated, correctly protected supply is easier to diagnose and less likely to be disturbed.
Installation and interference
A VHF installation is more than the radio. The antenna position, cable routing, connector quality and separation from other electronics all affect performance. Interference can come from a charger, inverter, LED driver, engine electrics or another transmitting device.
Note whether the noise changes with engine speed, when a charger is operating, when a particular light is switched on, or when another piece of equipment transmits. That is useful evidence even if the cause is not obvious.
If the problem appears only when another system is running, record which system and what changes. Intermittent interference is much easier to investigate when the triggering condition is known.
What to record before arranging a check
Include the radio make and model, the antenna type if known, and the vessel type. Describe whether the issue affects transmission, reception or both, and who can hear whom. Include any recent work on the mast, antenna, electronics or electrical system.
If you have another radio or handheld VHF, note what it can hear and transmit. A comparison helps separate a vessel-wide installation problem from a single radio fault.
- Radio make and model, if known.
- Antenna type and location, if known.
- Whether the fault affects transmit, receive or both.
- Any recent work on the mast, antenna or electronics.
- Whether other equipment affects the symptom.
- How the radio behaves with the engine running or off.
Why this matters before a trip
VHF is part of the vessel’s communication and safety equipment. A radio that appears to work at the berth may perform differently at distance, in poor weather or with the engine running. Testing it in the situations that matter is part of understanding the fault.
Do not rely on a single radio check at close range to confirm the system is healthy. If the performance has changed, record the symptoms and arrange a scheduled check before relying on it for a longer passage.
A practical next step
Start with the symptom pattern, the antenna history and the power supply. Maritime Electrical can discuss the likely areas to check and arrange a scheduled inspection where the radio, antenna, cabling and supply can be assessed together.
The aim is to find whether the limitation is in the radio, the antenna system, the installation or the supply, rather than replacing equipment without understanding the cause.