Garmin GMR FANTOM 18X Installation Instructions Manual page 4

Roof Mounting Considerations
NOTICE
If you are mounting the radar on a roof or hard top of your boat, you may need to raise the installation height
using a pedestal or other suitable structure to avoid a negative impact on performance. Mounting the radar
directly on a hard top could cause the transmitted energy to be reflected or absorbed by the surface. If the
surface is metal, this is particularly important to avoid.
The beam transmitted by this radar spreads vertically 12.5 degrees from the horizontal mid line , and you
should raise the dome so the beam clears the edge of the roof or hard top .
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