Article by Capt. Steve Katz
Loud and Clear
Even with today’s modern communications devices, cell phones, sat phones, Wi-Fi, InReach and EPIRB the marine VHF radio is still the best way to communicate to others on the water or land. Whether to find the best fishing spots, get a tow back to shore or a medical emergency, most maritime communication around the world is conducted over the VHF radio.
There are many different varieties of VHF maritime radios, beginning at around $150 for either a stationary radio (antenna extra cost) or a handheld VHF with a built-in antenna. Additional features, such as AIS, GPS, remote microphones, and color displays can bring up the costs to over $1000.
A maritime VHF radio transmits at a maximum of 25 watts, for a maximum range of about 25 miles between boats. A VHF radio signal transmits to the receiver radio by line-of-sight, so the taller the antenna at each location, the farther the range. As many of you know, the Coast Guard has very tall VHF antennas and operates with more power and special technology to send and receive communications over much larger distances than the average boater’s VHF radio. There are 49 VHF channels and two AIS frequencies authorized by the FCC/USCG and 7 weather channels used by NOAA Weather Radio; each channel is assigned a unique frequency between 156 and 162 MHz If you have a newer VHF radio, you may notice that there are “new” 4-digit VHF channels, these are not new frequencies, but a new numbering scheme of existing channels, as required by the International Telecommunications Union or ITU. For example, old channel 19A is now 1019 and old 78A is 1078.
For your VHF to send and receive properly, the radio needs a reliable source of the electrical power and a good antenna system. While a radio may function on a voltage lower than specified, the transmitting power output will be reduced and therefore the transmitting range too. As an example, the popular ICOM M506 rated output power is at a supply voltage of 13.8 volts.
The type, length and connections of the coax cable connecting the radio to the antenna can adversely affect the performance of your VHF radio. There are several types of coax cables available; the type of cable should be upgraded for longer runs due to potential signal loss.
As an example, a high performance RG-8X coax cable is 20% better in dB (power) transmission than the typical RG-58 coax cable. The connections (splices, adapters, and extensions) in the VHF coax wire can dramatically reduce the radio power from getting to your antenna.
A single splice in your coax run can reduce your performance by .5dB, try to avoid having any splices between the radio and the antenna. The higher the VHF antenna is mounted on the boat, the longer the range of your transmission and reception. Since VHF radio waves travel in a mostly straight line, if your antenna can “see” the other antenna, the radios should be able to send and receive with each other. Many antennas advertise a “gain in dB, or effective output power, this is gain (or apparent power amplification) is accomplished by the antenna design focusing the radio waves in a narrow beam, which is great if that narrow beam points to the intended distant VHF radio, otherwise you may not have much power, if any, radiated in other directions than the focused beam.
Testing – while there are a few tests a boater can conduct, the first and easiest test is to use your VHF radio call and talk to a friend on their VHF radio using an approved channel. They should be a meaningful distance away and you should ask the other party how they hear you and you should listen to see if their transmission to your radio is loud and clear. This tests both your send and receives functions along with your microphone and speaker.
If you have a VHF radio with DSC and it has been programmed with your MMSI number, you can use the USCG Rescue 21 system to conduct an automated VHF radio check. 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 another boaters VHF using their Maritime Mobile Service Identity (MMSI).
If you think you have a VHF problem, you should contact a professional technician who can test your VHF radio and antenna systems using specialized equipment and at a minimum determine the output power of your radio in watts and check yourw antenna system loss by calculating the VSWR.
Once you are sure you have a good working VHF radio, there are a few guidelines, rules and laws that you may need to be aware of: The USCG states “In general, any vessel equipped with a VHF marine radiotelephone (whether voluntarily or required to) must maintain a watch on channel 16 (156.800 MHz) whenever the radiotelephone is not being used to communicate”. This is one of the reasons many boaters have two VHF radios, one they leave on channel 16 and the other they use for recreational broadcasts. For those who have not been kept up-to-date, An FCC ship station radio license is no longer required for any vessel traveling in U.S. waters which uses a VHF marine radio, radar or EPIRB, and which is not required to carry radio equipment.
The information above is a good way to check and test your VHF radio to be sure it is performing at its best, allowing you to contact your fishing buddies or communicate with rescue authorities.§
