Marine VHF Radio: Complete Guide for Sailors

In 30 years at sea — on fishing vessels in the South Atlantic, on offshore support ships, and on private sailboats through the Patagonian channels — I've seen VHF save a life, and I've seen not knowing how to use it do exactly the opposite. It's not complicated equipment. But there are things you need to know before you need them.

What marine VHF is and what it's for

VHF stands for Very High Frequency. Marine VHF radio operates in the 156-174 MHz band and is the primary communication system between vessels, and between vessels and shore. Unlike a phone or satellite unit, VHF works without a subscription, without network coverage, and without relying on a phone battery. When the satellite has no signal and your mobile has no bars, VHF keeps working.

Its main uses are: coordination between vessels, communication with ports and marinas, receiving weather bulletins from the Armada, and distress calls. VHF is part of the GMDSS (Global Maritime Distress and Safety System) and it's the first piece of equipment rescue teams look for when a vessel calls for help.

Channel 16: the channel you never abandon

Channel 16 (156.8 MHz) is the international calling and distress channel. By international convention — and under Chilean Maritime Authority regulation — every vessel equipped with VHF must maintain continuous watch on channel 16 while under way. It's not a recommendation: it's an obligation.

Channel 16 serves three functions that must never be mixed:

• Distress calls: MAYDAY (immediate danger to life), PAN PAN (urgency) and SÉCURITÉ (safety notice to shipping)
• Call setup: contacting another vessel or a coast station. Once contact is established, you switch to a working channel (typically 9, 12, 14 or 22 depending on the area)
• Safety communications: maritime traffic notices, weather forecasts and Navy alerts

How to make a MAYDAY call

MAYDAY is used only when there is immediate danger to life: sinking, fire, collision, man overboard with no chance of recovery, serious flooding. It is not for minor breakdowns or to request information.

The standard procedure, on channel 16, is:

1. MAYDAY MAYDAY MAYDAY
2. This is [vessel name], [name] three times
3. Position: GPS coordinates or a clear geographic reference ("5 miles south of Punta Arenas")
4. Nature of the emergency: "we are sinking", "fire on board", etc.
5. Number of people on board
6. Any useful information: vessel type, colour, whether a liferaft has been deployed
7. "OVER"

Wait 10 seconds and repeat if there's no response. Keep repeating until you get an answer. The Chilean Navy monitors channel 16 across its entire network of coast stations.

PAN PAN and SÉCURITÉ

PAN PAN is the urgency call: a serious situation but without immediate danger to life. It's used for man overboard with a vessel nearby, a breakdown with collision risk, or a medical emergency on board. The procedure is similar to MAYDAY but begins with "PAN PAN PAN PAN PAN PAN".

SÉCURITÉ is for safety notices to shipping: a drifting obstacle, an ice zone, reduced visibility from fog. It's issued mainly by coast stations, but any vessel can transmit it if it detects a hazard to other mariners.

The DSC system: digital distress calling

DSC (Digital Selective Calling) is the digital complement to VHF. It operates on channel 70 and lets you automatically send a distress signal with your GPS position and vessel identifier (MMSI), with no need to speak. Within a second, every DSC unit in the area receives the alert with your exact position.

For DSC to work properly you need three things:

• A VHF unit with built-in DSC (practically every modern model has one)
• GPS connected to the VHF (internal or external) so it transmits position automatically
• An MMSI (Maritime Mobile Service Identity) number registered on your unit and with the Chilean Navy

Fixed VHF vs handheld VHF

Fixed VHF is installed on the vessel, usually at the nav station or helm. It has higher power (25 watts), longer range, and is connected to an antenna on the mast or superstructure. It's the primary unit and the one recommended for DSC.

Handheld VHF runs on its own battery and has lower power (typically 5 watts), which cuts range by half or more. Its advantage is that you can carry it on you at all times, including if you have to abandon ship. Many sailors carry one as a backup, stowed in the abandon-ship kit or in the liferaft.

For navigation in the channels of southern Chile, where mobile signal disappears, the ideal combination is: fixed VHF with DSC as the primary unit, plus a waterproof handheld VHF in the emergency kit.

VHF range and limitations

VHF operates line-of-sight, which means the curvature of the earth limits range. The practical rule: the higher the antenna, the greater the range. Between two recreational vessels with antennas 3-5 metres above the water, realistic range is 10 to 20 nautical miles. With a coast station or a large ship with a taller antenna, you can reach 30-40 miles.

In the fjords and channels of southern Chile, geography cuts range dramatically: mountains block the signal, and many narrow channels create shadow zones where you can't reach a coast station even 5 miles away. In those areas, the EPIRB and satellite communication become even more important.

Is VHF mandatory in Chile?

Yes, for most navigation categories. The Maritime Authority (Directemar) requires a fixed marine VHF with DSC to grant zarpe for coastal, cabotage and offshore navigation. For local navigation within a bay or sheltered waters it may not be a strict requirement, but the Harbour Master can require it depending on local conditions.

In addition, the VHF operator must hold the Restricted Radiocommunications Operator's Licence for Vessels, issued by Subtel (the Chilean telecommunications regulator). The process is straightforward and courses are available at several nautical clubs around the country.

What many sailors don't know about VHF

In my years as a Captain, I've seen several recurring mistakes that can be costly:

• Not having the MMSI programmed into the VHF — DSC transmits as "unknown vessel"
• Not connecting GPS to the VHF — DSC transmits without a position, which can delay rescue by hours
• Leaving the VHF on a working channel and not monitoring channel 16
• Not charging the handheld VHF — when you need it, the battery is dead
• Not knowing the MAYDAY procedure by heart — in an emergency there's no time to look up instructions
• Using channel 16 for ordinary conversation between vessels

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