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Complete Guide to Using VHF Radio Aboard Your Boat


What is Marine VHF Radio and How Does It Work


VHF is an abbreviation for Very High Frequency and is often used for short-range communications. VHF radio signals travel in a straight line, unlike HF or High Frequency radio signals which follow the curvature of the earth. Therefore, the distance that VHF signals can travel is limited. That limitation depends on several factors, the first being antenna height. The higher the antennas, the greater the distance. The next factor is signal obstruction, which is generally not a concern out on the water, unless you are boating in an area with tall buildings that may block VHF signals. The third factor is weather conditions, as heavy rains and thick clouds may also limit VHF radio signals. Generally you can expect good communication up to approximately 5 miles across open water, with taller antennas and higher signal wattage offering closer to 10 miles of range.


Should I use Fixed Mount or Handheld Marine VHF Radio


The answer to this question depends on how far from land you plan to go while boating. For those boats that remain within a few miles of shore and close to harbors and other vessels, a handheld VHF will be sufficient. For vessels that venture farther offshore, you will need a fixed mount VHF with at least an 8 foot tall antenna.


While handheld and fixed mount VHF radios operate the same, fixed mount radios offer higher signal output wattage, typically 25 watts with an option to reduce to 5 or 1 watt for close range communication. This higher wattage combined with a taller antenna height offers greater communication range.


Handheld VHF radios can be used on boats that remain close to shore as they are typically limited to 5 watts maximum output with a low setting of 1 watt. They have their own antenna built in, much like a walkie-talkie, so the antenna height is limited. This gives the handheld a shorter communication range. Handheld units make an excellent backup radio for emergencies on larger sized boats.


Why Do I Need VHF Radio if I have a Cell Phone


This is a very common thought process but if there is a life or death emergency situation, calling a mayday on channel 16 is the best way to summon help on the water. Not only will the Coast Guard and other marine authorities hear your call for help, but so will other boaters who may be in close proximity to you. On the water, oftentimes the first responders are other vessels that come to assist. By relying only on your cell phone, you could miss an opportunity to get help quickly.


What is MMSI and How Do I Set It Up


The Maritime Mobile Service Identity (MMSI) is a unique nine-digit identification number that is assigned to a VHF radio on a ship or other maritime vessel. The MMSI is used to identify the vessel and its VHF radio equipment to other vessels and coastal stations when help is needed. All fixed mount VHF radios, and increasing numbers of handheld radios, are equipped with an emergency distress button that when activated, transmits your GPS location and a distress call. By registering your radio with an MMSI number, additional information will be transmitted to emergency responders to assist them in locating and identifying your vessel.


To register and learn more about MMSI, please visit this page on the FCC Website.


What is AIS

The Automatic Identification System (AIS) is a marine tracking system that uses VHF radio signals to transmit and receive data about the position, course, and speed of ships. AIS is designed to improve the safety and efficiency of marine navigation by providing real-time information about the location and movement of vessels in a given area.

AIS consists of a network of transponders that are installed on ships and at coastal stations. Each transponder is equipped with a unique identification number and is capable of transmitting and receiving data about the vessel’s position, course, and speed, as well as other information such as the vessel’s name and type.

AIS data is transmitted and received using VHF radio frequencies, and it can be received by other vessels, coastal stations, and other AIS transponders within range. This allows vessels to be monitored and tracked in real-time, and it also allows them to communicate with each other and with coastal stations.

AIS is widely used in marine navigation and is considered an essential tool for improving safety and efficiency in the shipping industry. It is also used by other organizations, such as search and rescue agencies and government regulatory bodies, to monitor and track vessel traffic. The use of AIS is optional aboard recreational vessels. Some VHF radio units have a built-in transponder while other units require an external transponder to be connected.


Using Marine VHF Radio


The operation of the radio is very simple. If you have used a walkie-talkie, you have used a marine VHF radio. Here are some important functions to know about:


Channel 16/9 Button: Most radios are equipped with a button that will quickly allow you to get to channels 16 or 9, regardless of what other function you are currently using. This will allow you to make an urgent distress call without worrying about menus or settings.


Squelch Control: This function allows you to remove the static noise from distant signals. Generally you should tune the squelch button on your radio until the static noise has stopped.


Weather or WX Function: In days of old, the VHF radio was the way to obtain the most updated forecast while boating. Now there’s an app for that. However, weather alerts and warnings will still be broadcast over the VHF radio, so if you are out of cell phone range, be sure to set up the weather alert function on your radio.


DSC/Distress Button: Pressing this button will activate a distress call using the MMSI information discussed above.


Power/Volume Control: All VHF units are a bit different when it comes to the power and volume control, but in many cases they are configured as a multi-function button.


Remote Microphone Controller: Many modern VHF radios have a master unit installed in the vessel and multiple microphone/speaker controllers installed at each helm station.


Microphone Key Button: When speaking, press and hold the microphone button. When done speaking, release the button so that you can hear responses.


Choosing the right VHF Channel: Channel 16 is the primary channel that mariners should be listening to while boating. It is also the distress frequency should you need it. Here is the Federal Communications Commission official VHF Channel Guide.


Types of Emergency or Urgency Calls


SECURITE, which is pronounced securitay, is used to advise other mariners about navigational hazards. For example, if a tugboat is navigating through a narrow channel, the captain will often make a SECURITE call on channel 16 so that other vessels can avoid him.


PAN-PAN, which is pronounced pahn-pahn, is used when there is an urgent situation. Occasionally you will hear the Coast Guard use this to warn other boaters about a distress call that was heard or the sighting of a flare being launched.


MAYDAY calls require an urgent response. These are used when there is immediate danger to life or a vessel and assistance is required as soon as possible.


Especially with MAYDAY calls, you should say the word three times, then give your position in latitude and longitude and state the nature of your distress. If you don’t hear any response, make the call again. Be sure that your VHF Radio volume is turned up and that you are broadcasting on channel 16.


Marine VHF Radio Licensing


Since 1996, recreational boaters with vessels under 65 feet are no longer required to have a license to operate their radio as long as they are not traveling to a foreign port, which includes Canada, the Bahamas and the Caribbean Islands. Commercial vessels and those using single sideband still must obtain an FCC License. To learn more about marine VHF Radio licensing, please visit this page on the FCC website.


To learn more about using VHF radio, consider completing our on-the-water Boating Courses. 


Marine VHF Radio Naples

Marine VHF Radio Naples