Garmin GBR 21 - Manual (Page 10)

8
Mounting the Antenna
The supplied antenna coupler fits a standard 1-inch
antenna mount (not included). Like the receiver, the
antenna should be placed away from all sources of
interference. As a general rule, mount the antenna at least
three feet from all other antennas and the vessel’s electrical
system components (alternator/ignition system). Position
the antenna so that the clearest view in all directions is
obtained. The antenna coupler is supplied with 30 feet of
RG58 cable attached. When routing the cable to the GBR
21, observe the same precautions followed when choosing
mounting locations for the receiver and the antenna: Avoid
routing the cable near the vessel’s alternator or ignition
system components.
A ground strap is attached to the antenna coupler,
except on the GA 22/23 H-field antennas. For proper
operation, the ground strap must be connected to a vessel
(earth) ground. Do not ground the coupler to the electrical
system. If the coupler is not adequately grounded, the
beacon signal may be too weak for the GBR 21 to provide
reliable correction data.
Note:The GA 22/23 H-field antennas do not
require grounding.
1. Secure the antenna mount at the desired mounting
location.
2. Thread the antenna coupler/GA 23 onto the antenna
mount and hand tighten until snug. Do not over
tighten. Thread whip antenna onto coupler.
3. Connect the antenna coupler’s ground strap to a
vessel (earth) ground. A ground connection can
usually be made by connecting to a thru-hull fitting,
engine block, dynaplate or body of a metal vehicle.
4. Route the antenna cable to the GBR 21. Excess cable
should be coiled together and secured in an
inconspicuous location.
Modifications to the DGPS
antenna cable could result in undesired operation of
the GBR 21.
5. Connect the antenna cable to the BNC connector
on the GBR 21.
Installation
Mounting the
Antenna
The Interface Setup Page
may be selected from the
Main Menu on the GPS 12/
12XL/48. For additional
instructions, see the owner’s
manual for your GPS
receiver.
From the Interface Page,
select ‘RTCM/NMEA’ and
‘NMEA 0183 2.0’ to properly
communicate with the
GBR 21.