FCC ID: K6630283X3S
IC ID: 511B-30283X3S
GX5000S / GX5500S Operating Manual
7 GETTING
STARTED
7.1 ABOUT VHF RADIO
The radio frequencies used in the VHF marine band lie between 156 and 158 MHz with
some shore stations available between 161 and 163 MHz. The marine VHF band provides
communications over distances that are essentially “line of sight” (VHF signals do not travel
well through objects such as buildings, hills or trees). Actual transmission range depends
much more on antenna type, gain and height than on the power output of the transmitter.
On a fixed mount 25W radio transmission expected distances can be greater than 25 km.
7.2 SELECTING AN ANTENNA
Marine antennas are made to radiate signals equally in all horizontal directions, but not
straight up. The objective of a marine antenna is to enhance the signal toward the horizon.
The degree to which this is accomplished is called the antenna’s gain. It is measured in
decibels (dB) and is one of the major factors in choosing an antenna. In terms of effective
radiated power (ERP), antennas are rated on the basis of how much gain they have over a
theoretical antenna with zero gain. A 1 m, 3dB gain antenna represents twice as much gain
over the imaginary antenna.
Typically a 1 m 3dB gain stainless steel whip is used on a sailboat mast. The longer 2.5 m
6dB fiberglass whip is primarily used on power boats that require the additional gain.
7.3 COAXIAL CABLE
VHF antennas are connected to the transceiver by means of a coaxial cable, a shielded
transmission line. Coaxial cable is specified by it’s diameter and construction.
For runs less than 6 m, RG-58/U, about 6 mm in diameter is a good choice. For runs over 6
m but less than 15 m, the larger RG-8X should be used for cable runs over 15 m RG213
should be used. For installation of the connector onto the coaxial cable refer to the figure
below.
To get your coax cable through a fitting and into your boat’s interior, you may have to cut off
the end plug and reattach it later. You can do this if you follow the directions that are
supplied with the connector. Be sure to make good soldered connections.
8 INSTALLATION
8.1 LOCATION
The radio can be mounted at any angle. Choose a mounting location that:
• keeps the radio and microphone at least 1 m away from your vessel’s magnetic
navigation compass
Vertex Standard Co., Ltd.
8