GX2355S
Owner’s Manual
page 57
9.12 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 3 foot, 3dB gain
antenna represents twice as much gain over the imaginary antenna. The length of
the antenna you choose, however, must also be related to the size of your boat.
Typically a 3 foot 3dB gain stainless steel whip is used on a sailboat mast. The longer
8 foot 6dB fiberglass whip is primarily used on power boats that require the additional
gain.
9.13 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 20 feet, RG-58/U, about 1/4 inch in diameter is a good choice. For
runs over 20 feet but less than 50 feet, the larger RG-8 or RG-213/U should be used
for cable runs over 50 feet RG-8 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 come with the connector. Be sure to make good soldered connections.
1/16''
3/4''
3/4''
1 1/8''
1/8''
5/8''
3/8''
Adapter
