VHF Radio Installation Regulations: What the Rulebook Actually Says
VHF Radio Installation Regulations: What the Rulebook Actually Says
There is a moment that happens during every port state control inspection. The officer walks onto the bridge, looks at the VHF radio, and asks for the installation records. Most crews can produce the type approval certificate. Fewer can produce evidence that the installation itself actually meets the requirements.
That distinction matters. Type approval tells you the equipment passed the bench tests. Installation regulations tell you whether that equipment will actually work when you need it. And the difference between the two is where many vessels fail inspection.
We design and manufacture our own VHF communication equipment. We have seen installations that worked flawlessly for years and installations that passed the paperwork but failed the first real distress call. The regulations exist for a reason. Here is what they actually say.
The Legal Foundation: SOLAS Chapter IV
The carriage and installation requirements for VHF radio equipment come from SOLAS Chapter IV, which covers radiocommunications. The equipment must comply with the functional requirements throughout the intended voyage. That is not a suggestion. It is the legal baseline.
SOLAS Regulation IV/6 establishes the general installation requirements. Every radio installation must be located so that no harmful interference of mechanical, electrical, or other origin affects its proper use. It must ensure electromagnetic compatibility and avoid harmful interaction with other equipment and systems. It must be placed to ensure the greatest possible degree of safety and operational availability. And it must be protected against water, extremes of temperature, and other adverse environmental conditions.
These are not optional preferences. They are mandatory conditions that every installation must satisfy.
The Antenna System: Where Most Installations Go Wrong
The antenna is the most common point of failure in VHF installations. Not because the antenna itself is defective. Because it was installed in the wrong place.
IMO Resolution A.803(19), the performance standard for shipborne VHF radio installations, specifies that the VHF antenna or antennas should be vertically polarized and, as far as practicable, be omnidirectional in the horizontal plane. The installation must be suitable for efficient radiation and reception of signals at the operating frequencies.
The practical requirements go further. VHF antennas should be placed in a position that is as elevated and free as possible, with at least two metres horizontal separation from constructions made of conductive materials. The antenna should not be installed close to any large vertical obstruction. The objective is simple: the antenna needs to see the horizon freely through 360 degrees.
The separation requirements are specific. VHF antennas should have a vertical polarization. Ideally, there should not be more than one antenna on the same level. If multiple antennas must share the same level, the distance between them should be at least five metres. The distance to VHF antennas should be more than four metres. The distance to the magnetic compass should be more than three metres.
For AIS VHF antennas, the guidance is even more detailed. The antenna should be installed safely away from interfering high-power energy sources like radar and other transmitting radio antennas, preferably at least three metres away and out of the transmitting beam. The AIS VHF antenna should be mounted directly above or below the ship's primary VHF radiotelephone antenna, with no horizontal separation and a minimum of two metres vertical separation. If it is located on the same level as other antennas, the distance apart should be at least five metres.
The Cabling Requirements That Get Overlooked
The cable run is where many installations introduce losses that degrade performance. The guidance is clear: the cable should be kept as short as possible to minimise attenuation of the signal. Double screened coaxial cables equal to or better than RG214 are recommended.
All outdoor installed connectors on the coaxial cables should be waterproof by design to protect against water penetration into the antenna cable. Coaxial cables should be installed in separate signal cable channels or tubes and at least ten centimetres away from power supply cables. Crossing of cables should be done at right angles. Coaxial cables should not be exposed to sharp bends, which may change the characteristic impedance of the cable. The minimum bend radius should be five times the cable's outside diameter.
Coaxial down-leads should be used for all antennas, and the coaxial screen should be connected to ground at one end. The recommended maximum loss is three decibels.
The Power Supply Requirements
A VHF radio is useless without power. SOLAS Regulation IV/13 requires that there shall be available at all times, while the ship is at sea, a supply of electrical energy sufficient to operate the radio installations and to charge any batteries used as part of a reserve source of energy.
A reserve source or sources of energy must be provided on every ship to supply radio installations for distress and safety radiocommunications in the event of failure of the ship's main and emergency sources of electrical power. The reserve source must be capable of simultaneously operating the VHF radio installation.
The duration requirements are specific. For ships provided with an emergency source of electrical power that complies fully with SOLAS regulations, the reserve source must supply the radio installations for at least one hour. For ships not provided with such an emergency source, the requirement increases to six hours.
The reserve source or sources of energy need not supply independent HF and MF radio installations at the same time.
The Operational Location Requirements
Where the equipment is placed on the bridge matters as much as how it is installed. Control of the VHF radiotelephone channels required for navigational safety must be immediately available on the navigation bridge, convenient to the conning position. Where necessary, facilities should be available to permit radiocommunications from the wings of the navigation bridge. Portable VHF equipment may be used to meet this provision.
In passenger ships, a distress panel must be installed at the conning position. This panel must contain either one single button which, when pressed, initiates a distress alert using all radiocommunication installations required on board, or one button for each individual installation. The panel must clearly and visually indicate whenever any button has been pressed. Means must be provided to prevent inadvertent activation.
The Lighting and Marking Requirements
The equipment must be provided with reliable, permanently arranged electrical lighting, independent of the main and emergency sources of electrical power, for the adequate illumination of the radio controls. Every radio installation must be clearly marked with the call sign, the ship station identity, and other codes as applicable.
The harmonization guidelines expand on these requirements. All radio equipment should be clearly marked with its type designation, visible after installation. The radio installation should be marked with the ship's GMDSS identities, including call sign, MMSI, EPIRB hexadecimal identity, and equipment serial numbers. DSC operation procedures should be posted near the DSC equipment on the navigation bridge, and emergency procedures should be posted near the relevant equipment.
The 2028 Deadline That Changes Everything
Here is something that will catch many operators off guard. The IMO issued MSC.1/Circ.1460/Rev.5 in January 2025, which sets a hard deadline for VHF equipment upgrades. All VHF communication equipment installed under SOLAS regulations IV/7.1.1, 7.1.2, and 7.1.6 must be upgraded to comply with the latest channel arrangements in Appendix 18 of the ITU Radio Regulations. The deadline is the first radio inspection after 1 January 2028.
The ITU made significant revisions to Appendix 18 at the 2012, 2015, and 2019 World Radio communication Conferences. The key changes include the full implementation of 12.5 kHz narrowband channelization, protection of AIS channels 87B and 88B for data transmission only, and the clear designation of channel 70 as DSC-only with no voice traffic allowed.
If your existing VHF equipment does not support these new channel arrangements, it will need a software or hardware upgrade. Some older units may not be upgradeable at all and will need replacement. The deadline is not optional. Fail to comply, and your vessel could face detention during port state control inspections.
The Harmonization Guidelines
The most current guidance comes from COMSAR.1/Circ.32/Rev.3, approved by the 109th session of the Maritime Safety Committee and disseminated on 13 December 2024. These guidelines supersede the previous Rev.2 version.
The guidelines reinforce the general requirements. Every radio installation should be located to prevent harmful interference of mechanical, electrical, or other origin. It should be situated to ensure electromagnetic compatibility and to avoid harmful interference with other equipment and systems. It should be placed to ensure the highest possible degree of safety and operational availability, with appropriate warning notices. It should be protected against the harmful effects of water, extreme temperatures, and other adverse environmental conditions. It should be equipped with reliable, permanently arranged electrical lighting-independent of the main and emergency power sources-for adequate illumination of radio controls. And it should be located such that no magnetic compass lies within the stated Compass Safe Distance of the equipment.
Why Installation Regulations Matter
The installation regulations exist because a VHF radio that passes type approval can still fail in service if it is installed incorrectly. The antenna must see the horizon. The cables must be shielded and grounded. The power supply must be redundant. The controls must be accessible from the conning position. The lighting must work when the main power fails. The markings must be visible.
We design our VHF equipment to meet these installation requirements, not just the type approval standards. Because we have seen what happens when a vessel installs a compliant radio in a non-compliant location. The range drops. The DSC alerts fail. The inspection fails.
The regulations are not suggestions. They are the legal minimum for safe operation. And the vessels that follow them are the vessels that pass inspection and stay operational.
