Everything you need to know about maritime VHF communications

A VHF VHF radio is an essential means of communication on the water. Whether you are passing through locks, addressing bridge keepers, communicating your position in busy waters or in distress: clear and reliable communication can make all the difference. In this article we explain what a VHF radio is, what types there are, which certificates are required, what ATIS and MMSI mean, which channels are relevant with VDES, the advantages, and why bridge keepers prefer VHF calls to telephones.

What is a VHF radio and how does it work

A VHF radio is a radio communication device that uses Very High Frequency (VHF) frequencies. With a VHF radio, you can both transmit and receive via fixed shipping channels. This allows you to maintain contact with bridge keepers, lockkeepers, traffic posts and other ships. In emergency situations, the VHF radio is indispensable: a call on channel 16 is immediately picked up by shipping and emergency services. The system is robust, not dependent on mobile networks and standardised, reducing the risk of misunderstandings.

Fixed radio vs handheld radio (handheld)

There are roughly two types of VHF radios: the fixed radio and the handheld (also called handheld). A fixed system has more features and range, while a handheld radio is useful as a back-up or for use on smaller vessels. The main differences are listed in the table below.

Feature	Fixed VHF radio	Handheld radio
Antenna	External VHF antenna, positioned higher → better range	Small antenna on device, lower → more limited range
Power	Higher/adjustable (at sea often up to 25 W)	Lower power due to battery/antenna
Power supply	Fixed on-board power supply, robust	Battery/battery; charging required
Functionality	More buttons, better audio; additional handset possible	Simpler, portable; backup
Ease of use	Always installed, immediately available	Portable, but carrying/charging
Commitments (NL)	At >20 m mandatory; registration & certificate	Allowed with certificate; often no duty on small pleasure craft

Certificates

Operating a VHF radio is only allowed if you hold the correct certificate. There are different certificates, depending on sailing area and type of equipment:

Basic Mariphony Certificate: required for use on inland waterways.
Marcom-B: needed when using DSC and on coastal waters.
Marcom-A: for global communications, including MF/HF equipment.
SRC (Short Range Certificate): International certificate similar to Marcom-B.

ATIS & MMSI explained

Using a VHF radio involves identification codes. Two concepts come into play:

ATIS (Automatic Transmitter Identification System) is mandatory on most European inland waterways. With every transmission, the VHF radio automatically sends a unique code, so traffic stations and bridge operators can immediately see which vessel is calling.

MMSI (Maritime Mobile Service Identity) is an international 9-digit code, required in DSC-featured VHF radios and AIS equipment. It ensures unambiguous identification of ships worldwide.

DSC marine radios always have a built-in or connected GPS. A DSC distress call automatically includes the vessel's coordinates.

With the help of a multiplexer this GPS signal can also be shared via WiFi with, for example, an iPad or other mobile device without its own GPS. That way, you make the most of the information your VHF radio collects.

VDES channels that are now standard

VDES (VHF Data Exchange System) is the successor to AIS and extends existing VHF communication with digital data. VDES can be used to exchange traffic information, safety messages and weather reports, among other things. Modern VHF radios are often already prepared for this technology, allowing them to process and transmit not only voice but also data in the future.

When is a VHF radio mandatory?

The rules for VHF radio use vary by country and sailing area. In the Netherlands, a VHF radio is mandatory for vessels longer than 20 metres. For smaller pleasure craft, use is usually not mandatory, but strongly recommended - especially on busy waterways or at sea.

Important: you always need a valid certificate to operate the VHF radio, and the equipment must be registered with the RDI (including ATIS and possibly MMSI code).

Benefits of a marine radio

A VHF radio offers several advantages over other means of communication:

✅ Independent of mobile networks and therefore more reliable.
✅ Direct contact with bridges, locks, traffic stations and other vessels.
✅ Safety: emergency calls are widely picked up and standardised.
✅ Transparency: other ships hear the call and know what is going on.
✅ Meets legal requirements and international standards.

Why bridge officers prefer a VHF call to a phone call

Although some skippers choose to call a bridge by phone, bridge operators clearly prefer VHF communication. A call by VHF radio arrives immediately, is recognisable and standardised, and makes it immediately clear which vessel is seeking contact (thanks to ATIS or MMSI). Telephone calls lack that clarity, and also take more time to transmit data.

Practical tips: installation, power, programming

Some tips for optimal use of the VHF radio:

Place the antenna as high as possible for maximum range.
Make sure ATIS and MMSI are entered correctly; errors lead to problems or fines.
Use the right mode:
inland water → low power with ATIS,
marine → high power with DSC/MMSI.
Keep handhelds charged and carry spare batteries.
Test regularly whether the VHF radio is functioning properly and can be understood.

The VHF channels of bridges, locks and harbours are indicated on signs along the water. In addition, they are easily found in the Waterkaarten app, so you always know which channel to call.

Overview of frequently used VHF channels

Channel	Use
1	CMIJ: info/weather/boating reports for IJsselmeer, Markermeer and randmeren.
2	Wadden - Brandaris area: listening out for messages and safety.
4	Central Reporting Station Wadden Sea: information/messages Wadden.
5	Wadden: sector/reporting channel (regional; follow local instructions).
6	Ships mutually at sea / safety alignment.
10	General traffic between vessels (intership) on inland waterways; listening out in poor visibility.
13	Bridge-to-bridge/intership on busy routes; alternative to 10.
16	Emergency, urgent, safety and call (at sea continuous listening out).
18, 20, 22	Bridges and locks (block/object; exact channel on blue VHF sign on site).
23	Coast Guard: weather and safety (MSI) messages at fixed times.
31	Marinas/pleasure boating: signing on/off, mooring information.
68-69	Match management/race services; sometimes rescue team at events.
72 & 77	Social/ship-to-ship (chat) for pleasure craft; do not use in port/VTS sector.
73	Match management or organisation (regional, at events).
78-82	Marina/port service (regional); see harbour information or sign-in board.
83	Coast Guard: weather and safety (MSI) messages at fixed times.
1027-1028	New simplex voice channels (replacing 27/28); some bridges/locks or shore stations use them.

Note: allocations are partly regional and sometimes change; always follow the blue VHF sign locally and consult recent VTS/port guide.

A VHF radio is not a luxury, but an essential safety tool on the water!

It provides reliable communication, makes you more visible and recognisable to other ships and shore stations, and meets legal requirements. Whether you choose a hand-held radio or a fixed installation: always make sure your equipment has the right certificates, correct registration and proper maintenance. That way you sail more safely and with more security.