Today's boaters have a variety of communication devices available for communication within coastal waters. In most areas, once a vessel is a few miles off shore, only VHF or Satellite communication will be available to communicate to coastal stations. The minimum standard for marine radio communication is a VHF marine radio. A VHF radio can be used to communicate with other vessels, marinas, the Coast Guard, or any other VHF marine radio. VHF range is limited to "line-of-site" between the transmitter antenna and the receiving antenna. As shown below, this is greatly influenced by the height of the transmitting and receiving antenna and their relation to the curvature of the Earth.
In addition to standard analog radio wave communication, a current marine VHF radio will also support DSC (Digital Selective Calling) which supports digital communication and enhances range and clarity, and reduces cross-talk on crowded channels. Depending on your location, the range of your VHF marine radio's ability to communicate to the US Coast Guard (via DSC) will be mostly dependent on the height of the Coast Guard radio tower. Below is an example of Coast Guard Sector St. Petersburg, and the estimated DSC coverage areas.
DSC has several advantages in a distress situation including the ability to send an unmanned distress signal to the Coast Guard by pressing the red distress button located on all VHF radios that support DSC. The distress signal will include the Latitude and Longitude of the vessel if the VHF has an embedded GPS unit or is connected to the boat's chartplotter.
DSC also enables direct calls to other DSC equipped VHF radio's using an assigned MMSI (Maritime Mobile Service Identity) number that works almost like a phone number.
To fully utilize the benefits of the marine VHF communication, a vessel operator should be familiar with the proper usage of their VHF radio and be proficient as follows:
Initiate a DSC distress signal
Issue a Mayday call to the US Coast Guard
Hail the US Coast Guard for non emergency purposes
Hail Tow Boat US or other tow service
Communicate with marina or other marine service resources
Hail other vessels using normal channels and MMSI/DSC
Listen to NOAA weather broadcasts
VHF Radio Tests
Boaters travelling further than 10-15 miles offshore, should consider an EPIRB (Emergency Position Indicating Radio Beacon) or PLB (Personal Locator Beacon). Both devices use satellite communication to relay distress and location information to the Coast Guard. In addition, some PLB products can send text messages and non-emergency location updates.
Making Sure Your VHF Works
A VHF radio is a critical piece of safety equipment that is often located in exposed areas and must be tested regularly to ensure proper functionality. There are two testing methods each with their own benefits and drawbacks.
Method 1 - Traditional Radio Check
The traditional radio check is simply a request on a shared channel for a reply from another VHF user. Although traditional checks are frowned upon by those concerned with overcrowding shared channels, there simply is no other effective means to test the analog capabilities of the VHF radio.
A traditional radio check should be performed on Channel 9, 68, 69, 71, or 72, and should not be requested on Channel 16. The validity of the test depends on your location relative to the person responding to your broadcast. A successful test with someone nearby does not necessarily mean the VHF is capable of communicating at a distance of 10 miles or greater, for example.
A valid check should be conducted as follows:
Tune to the preferred channel
Use the "Lo" (1-Watt) power setting for initial testing
Key the mic, "radio check, radio check, this is "Boat Name" in "General Location”
Wait for a reply and request further information regarding the location of the responding party if it is not initially provided
By completing this initial test, you have confirmed the functionality of the microphone, the transmitter, the receiver and antenna connection. It is useful, particularly if you venture offshore, to test your VHF while at a greater distance using a higher power setting and determining the distance to a responding vessel or station.
Method 2 - DSC Radio Check
Use your VHF's DSC capability to perform a test of the DSC functionality. Per the USCG, DSC based testing can be conducted as follows:
"For VHF DSC radios equipped with the Test Call feature, test transmissions should be made to the US Coast Guard MMSI 003669999 to receive an automated VHF DSC test response. You must use the “Test Call” category of your radio because “Individual” category calls to this address will not receive an automated response. For older radios not having a test call capability, testing can only be performed by using a routine individual call to their Maritime Mobile Service Identity (MMSI)."
The following video demonstration was performed on a Standard Horizon HX890. Although testing should work on any DSC capable device on any channel, is it advisable to use channel 70 as this is a dedicated safety channel and will produce an audible confirmation in addition to an acknowledgement message on most devices.
Although many people advocate the use of DSC based testing only, it doesn't test all the capabilities of the device including the analog and microphone functions.
The bottom line, if you really want to test the full functionality of your VHF radio, it is best to perform both a Traditional Radio Check and a DSC Radio Check.