Can you hear me now?
Having a VHF radio on a boat is always a good idea. It allows you to communicate with other boats, marinas, and rescue services if necessary. I have two on my boat, one a handheld and the other a fixed set. Fixed sets have a maximum radiated power output of 25 watts, while handhelds normally have a maximum output of 5 watts. The more power a transmitter has, the farther its signal can travel. The height of the antenna also affects how far away a signal can be heard, and the antenna for a fixed set is normally mounted at the top of the mast, which helps increase range.
To get the most from a fixed VHF radio, it has to be installed properly. Where it is situated on a boat depends on many factors, including the space available (usually at the chart table or in the wheelhouse), where the antenna will be sited, and the availability of a suitable power supply.
We hooked up a typical VHF set, the Uniden 525, and coupled it to a Glomex antenna. To make the process easier to follow, we mounted the radio on a mockup of a cut-away chart table.
Choosing an antenna
Choosing the right antenna is just as important as selecting the radio itself. A transmitter's power output will be wasted if it is coupled to the wrong antenna. Antennas come in various shapes and configurations, depending on the job they are expected to perform. The manufacturer's specifications will include a value for gain, expressed in decibels (dB). An antenna with a gain of 3dB is appropriate for a sailboat; for a powerboat you'll want a high-gain antenna in the 6dB range. An antenna's gain affects the way that a signal is propagated, or sent. A sailboat tends to roll and pitch more than a powerboat, and a lower-gain antenna sends out a signal in a wider arc than a higher-gain antenna.