Clear Comms: Marine VHF Explained - PassageMaker
Set your VHF up for safety

Your VHF radio is your lifeline for safety and rescue and they are often not used correctly, too late, or not at all. If you are interested in learning more about boating safety check out Mario's Boaters University course, Safety and Rescue at Sea at Boaters University. Use the promotional code PASSAGEMAKERfor 20% off.

Most of my career in the USCG was spent listening to the radio. Flying over the ocean, looking for the lost or otherwise missing, I was always tuned in and scanning the VHF band. Listening to what boaters said—and didn’t say—I learned over the years that radios are frequently misused, their capabilities are misunderstood, and very few know how to use them properly in an emergency.

In the helicopter, I was usually too busy to chime in with a correction when a long conversation was taking place on Channel 16 or one vessel was ignoring the calls of another. Other boaters could always be counted on to call the novice out for his mistake and egos were beaten up pretty regularly. But the problem is more than just one of etiquette, knowing the channels, and the responsible use of the airways. In an emergency, handling your radio incorrectly can cost you a lot more than your pride. Knowing everything you can about your VHF can mean the difference between making it home and not.

My most generous guess is that one radio in ten is properly installed and set up. Making sure you are on the good side of that guess means doing three things that most boaters never do: verifying the installation, connecting the GPS, and registering the radio. Too often a radio is installed by simply screwing the antenna into the back and with one radio check the installer claims success. A radio installed this way forfeits most of its emergency capabilities and may have a poor transmit range of only a few miles.

Standing Wave Ratio

To ensure the maximum power output of any radio (VHF or otherwise) you’ll want to verify the installation by measuring the standing wave ratio (SWR) between the radio and the antenna. Not doing this can cost you significant range.

Wires and antennas can eat power, weakening the signal. The SWR measures the electrical balance between your radio and the antenna. The lower the ratio, the stronger the signal you can transmit. High SWR (greater than 2.5 to 1) most often points to dirty or bad connections, worn or old wiring, or, less often, a poor antenna. You’re hoping for 1.5 to 1 or better, but you’ll likely need soldered connections to achieve that. If all of this has you scratching your head, that’s okay. Go to NMEA.org and find a Certified Marine Electronics Technician (CMET) in your area. Techs can check your install and make sure you are getting all the power you can out of your radio.

GPS Connection

The next thing so often left undone by boaters is connecting the boat’s GPS to the VHF. A CMET can help with this too, but it is usually pretty simple and the instructions are always listed in the owner’s manual. Yours may have GPS built in, but if not, making this connection will be a game-changer should you ever have to hit that little red button marked “Distress.” Used properly, that little red button makes your VHF a super-radio.

Once you push “Distress” and you tell the Coast Guard who you are, the name of your vessel, your contact ashore, your exact location, and the nature of your emergency, you will also be simultaneously sending a distress message to every vessel with an antenna in line of sight with yours. Your EPIRB can’t do that. Your cell or satellite phone can’t do that. AIS can’t do that. To make it all work, however, you have to get a maritime mobile service identity (MMSI) number and register your radio. Without this small (and free) effort on your part, you are giving up arguably the best distress communications tool for near-shore emergencies ever invented. Don’t be one of those boaters.

Know Your Channels and Power

Your VHF owner’s manual also includes instructions for setting “Dual Watch” or “Triple Watch” scans. Your radio can be programmed to listen on 9, 16, and 22, the three channels I recommend for a constant listening watch. I don’t think you need to memorize them, but you should have a list of all channels next to the radio so you use only the ones you should and stay off the ones you shouldn’t. Searching “VHF channels list” online will net you several options for an easy printout.

When making a call to another vessel or to the Coast Guard, always be conscious of that high/low power setting. On your radio, this is usually a button marked “H/L.” You should use the low power setting when talking to boats at close range or when you are in high-traffic areas. The high setting (25 times the power) is for really reaching out in an offshore emergency. Using low power whenever possible makes everyone safer. It means that someone in distress 15 miles away won’t be “stepped on” by you hailing your friends.

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Good Day or Mayday

In my life, I’ve never heard a boater call “Pan Pan.” The “Pan Pan” call is the distress communication that is supposed to come before “Mayday.” When a boater calls “Mayday” because the water is up to their ankles, they should have called “Pan Pan” when they first noticed the leak coming in around the shaft seal.

If you smell smoke on your boat and you can’t figure out where it is coming from, call “Pan Pan.” If you are having navigation issues and aren’t sure where you are in the world, ask the boaters around you for help.

In all that time listening to boaters on the radio, the worst thing I ever heard was silence. The most egregious misuse of the VHF marine radio is that they are often used too late or not at all. Set up correctly, and with a little knowledge and practice, your radio is the best tool you have to avoid trouble or to call for help if you can’t. 

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Mario Vittone is a retired U.S. Coast Guard helicopter rescue swimmer, who for 22 years rescued boaters in distress from the turbulent waters of the Atlantic Ocean and Gulf of Mexico. He served two tours as a rescue swimmer at Air Station Elizabeth City, North Carolina, and one at Air Station New Orleans, Louisiana. Vittone was also an instructor and course developer at the Aviation Technical Training Center in Elizabeth City before retiring in 2013. An expert in immersion hypothermia, drowning, sea survival, and safety at sea, he today writes and lectures on boating safety and search-and-rescue topics for popular print publications.

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