User's Manual

Line-of-Sight Requirements Satellite Data Modem (SDM) Installation
5-4 1/9/06 80-J4866-1 Rev. A
ALL INFORMATION SUBJECT TO CHANGE
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Line-of-Sight Requirements
The SDM requires an unobstructed line-of-sight view to the satellite in order to clearly send
and receive signals. The SDM must be able to send and receive the signals at a 12° angle
above the horizontal plane of the unit. There must be an unobstructed view of the satellite at
all angles above 12°.
The following illustration shows this 12° angle as well as the maximum allowable height of
objects located at various distances from the SDM centerline. This height is measured up
from the horizontal plane of the SDM.
An obstruction height of 2.5 inches for every 12 inches away from the SDM centerline is
acceptable. The MCP may not operate properly if there are obstructions above this height.
Use this same formula to verify that a trailer hooked up to the vehicle does not extend above
the 12° angle.
Normally, the satellite signal can pass through thin layers of glass, fiberglass, and plastic.
Thick layers or obstructions above the 12° angle may block the satellite signal.
The components listed below can block or severely reduce the signal from the satellite. These
obstructions can cause “blind spots.” It may not be possible to completely eliminate blind
spots but they must be kept to an absolute minimum:
Multiple layers of fiberglass, glass, or plastic
Areas with numerous bends in the fiber glass
Metal and wood bracing
Metallic paints and lead-based paints
Company logos that contain metallic materials
Common obstructions on vehicles include metal airdams, metal wings, metal side skirts, air
conditioning units, and exhaust stacks.
When mounting an SDM, make sure the mounting surface is strong enough to support the
weight of the SDM and mount (~6 pounds total weight). The installation must also withstand
very strong shock forces exerted by the truck when it is moving.
Maximum Height: 2' 6"
Maximum Height: 2' 1"
Maximum Height: 1' 8"
8' 10' 12'
12
Distance From
Centerline
Horizontal
Plane
Satellite
signals
OM/E-0093-42