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VHF Radios

Next to the PFD, a working vhf radio should be one of the top priorities for your boat.  A VHF radio can be useful for getting help, but also will allow you to help someone else, and listen for important weather or other information.

In this day of cellular telephones, the usefulness of a VHF radio can be forgotten.  The cell phone can be helpful on a boat, but should be used as a backup rather than as a replacement for a VHF radio.  A cell phone can be used to place a call for help, but signal strength may prevent the call from being made.  A VHF radio, on the other hand, can be heard by any one within the transmission range of your radio.   The VHF radio, generally is a "line of sight" instrument, i.e.  it will transmit about as far as you can see.  This usually is limited to about 25 miles. Handheld radios transmit a much shorter distance ( see next section ). A significant advantage to the VHF (very high frequency) radio is that your distress call can be heard and relayed by another boat should you be out of range of a Coast Guard Station.  Anyone hearing your distress call can come to your aid.  In fact, if you have  your VHF radio turned on, you must monitor channel 16, the distress and hailing channel.  Most VHF radios also have weather frequencies that allow you to monitor changing weather patterns.  

The utility of a handheld VHF radio is undeniable.  It is relatively compact, can be carried from boat to boat, or on to a tender and can be taken with you should you need to abandon your boat.  However, a handheld has significant limitations.  Its transmission power is generally 6 watts or less and it has a short antenna.  A fixed VHF radio typically has 25 watts of transmitting power and a much taller antenna.  Having 4 times more power  seems like the major advantage over a handheld, but actually the large antenna of a fixed unit is its major advantage.  The transmission distance of a VHF radio is directly related to its antenna height. Typically, a handheld will be able to transmit 6 to 10 miles whereas a fixed unit with an 8 foot antenna will be able to transmit 25 miles.  Almost all of the difference is related to the antenna size.    A small handheld VHF radio transmits its radio waves in an almost circular shape.  The taller the antenna, the more elliptical the transmission pattern.  This elliptical pattern is horizontally oriented and is the reason the taller antenna has its longer reach. This Standard Horizon radio, relatively new on the market, has two additional features not previously seen on a handheld radio, GPS and DSC. DSC is an acronym for Digital Select Calling. This feature is a part of the Coast Guard's modernization of our nation's marine communications known as Rescue 21. As the name indicates, DSC is a digital transmission over channel 70 in the vhf spectrum. You must register any radio with DSC to be able to use the feature. Once registered, your radio will have a unique MMSI number ( Maritime Mobile Service Identity ). When you register, you give important details to the Coast Guard including the name of the vessel, type and length of vessel, home port, emergency contact information, and owner information. DSC can also be utilized to privately contact another vessel with a known MMSI number. This is akin to having a contact number of another cell phone. The receiving station can send a digital response. Communications would then be established by voice on a working channel such as vhf channel 68. All newly manufactured radios must have DSC. A future boating education article will go into further detail about DSC, an important innovation in marine communication.

The CB radio should not be used as a primary vessel radio.  The most significant reason is that it is not a marine radio.  The Coast Guard monitors channel 16, the VHF distress channel, but does not monitor CB channels.  Typically other boaters do not monitor CB channels either.  These flaws make the CB radio almost useless for communication on the water.

In a previous section, antenna height was mentioned as being the most important determinant of transmission distance.  If you have decided to  purchase a fixed VHF unit for your boat, you will need to pick an antenna.  Antennas come in different "gain" sizes.  Gain is a direct measure of the transmission distance.  As mentioned previously,  antenna length is the primary determinant of gain.  Although somewhat oversimplified, generally the following gain relationships hold:

4 Foot Antenna 3 db
8 Foot Antenna 6 db
12 Foot Antenna 9 db

All things being equal, a 12 foot antenna would be the best choice for a boat.  However, the size of the boat enters into the picture.  A typical runabout used on Lake Tahoe or Pyramid lake will be in the range of 18 to 26 feet.  An 8 foot antenna with 6 db gain would probably be the most appropriate antenna for these boats.  If you are not familiar with installing a VHF antenna, have your dealer assist you.  A good connection to your radio is crucial for maximum transmission range and clarity.   Many of these connectors require soldering and coaxial cable can be difficult.  Newer non-soldered connectors made by Shakespeare Corporation work exceptionally well when used with coaxial cable.

At one time, the Federal Communications Commission required that VHF radios be licensed.  This requirement is no longer true as long as the unit is used in US waters.  A VHF radio used in international waters still must have a "station license" given by the FCC.

A VHF radio is by definition, a marine radio.  Technically, it can only be used on the water.  Once you are on shore, a VHF radio should not be used, according to FCC rules. There is some discussion about changing this rule to allow someone on shore to use a handheld to contact a boat on the water.

Channel 16 is the distress and hailing frequency that is monitored by the Coast Guard and other boaters.   That is the channel that should be used for an emergency.  Hold the microphone about one inch from your  mouth and speak slowly and distinctly.