VHF ANTENNAS
The choice of antennas available for marine VHF radios is large and confusing. To squelch the noise and help you cut through the clutter when shopping for a marine VHF antenna, I’ve compiled a group of essential considerations for you to use. While not every facet of antenna selection is covered, the information presented here should help you make a good buying decision.
LENGTH AND HEIGHT
VHF range is determined by the height of both the transmitting and sending antennas. So, a taller antenna will provide more range— but doubling the antenna’s height doesn’t mean transmission is twice as far. Again, depending upon the height of the other antenna, the difference can be as much as 20 percent farther or a little as 5 percent, again depending upon the other boat or shore station’s antenna.
LENGTH AND GAIN
A longer antenna has a higher gain, measured in decibels. This relates to the shape of the waves emanating from the antenna. Higher gain is more elliptically shaped, and so reaches a bit farther than the nearly round shape of lowergain antennas. Most 8-foot VHF antennas are 6 dB, while a 4-foot antenna is usually 3 dB. Again, a longer antenna results in somewhat longer range.
CABLE
Standard, or basic, coaxial cable for marine antennas is labeled RG-58A/U, which has a diameter of 0.194 inch. RG8X cable has much lower loss—more of the radio’s power actually gets to the antenna. RG8X has a diameter of 0.242 inch (so you may need to redrill a hole if replacing smaller RG58A/U cable), has very low loss, and is absolutely recommended for the best performance and any cable run more than 15 feet.
CONNECTIONS
Many newer antennas, whether from AirWave Marine (airwavemarine .com), Glomex (glomex.us) or Shakespeare (shakespeare-ce.com), offer an innovation we applaud: a connection at the antenna end of the cable that allows for replacement of a broken antenna without having to rerun cable through the boat and through the maze of a top or tower. Each manufacturer offers its own twist on this philosophy, but I would strongly recommend this type of antenna, all other considerations being equal. In fact, I just installed such an antenna aboard my personal boat.
WHIP ANTENNAS
Short antennas (often 3 feet long) are often called “whips.” These can be made of fiberglass or a stiff stainless-steel wire, and are ideal for small boats, such as smaller bay boats, flats skiffs and runabouts. Aboard such vessels, taller antennas would be cumbersome to mount, and besides, many such craft don’t venture far from port or the company of other boats, and so do not need the range provided by a taller antenna.
EMERGENCY ANTENNAS
Having a backup antenna makes good sense, should your primary antenna fail due to a low bridge, high tide, rough seas, or simply age and use.
One unique example is the INFL8-5 inflatable antenna from Shakespeare. This stows in a compact satchel yet inflates to a 5-foot-long, 3 dB antenna. It even comes with an adapter so you can connect a handheld VHF to it should your main radio go kablooey.