Site preparation
3-4 Chapter 3: Installation 99-145912-A
3.2.2 Obstructions (ADU shadowing)
The ADU is stabilized in 3-axis (plus skew) and can be used in
environments with elevations of -25° to + 125° to allow for continuous
pointing even in heavy sea conditions. The ADU beam is approximately
1 m in diameter for the first 30 m from the ADU. Beyond 30 m the
beam gradually widens so that it is approximately 5 m in diameter at
100 m distance. This beam expansion continues with increasing
distance. Any obstructions, such as masts, funnels, bridge house etc.
within this field can cause signal degradation or signal loss.
For optimum performance adhere to the following guidelines:
1. Place the ADU so that it has as much free line-of-sight as possible
without any structures in the beam through one full 360 degrees
turn of the vessel.
2. Do not place the ADU close to large objects that may block the
signal.
3. Elevate the ADU by mounting it on a mast or on a mounting
pedestal on a deck or deck house top to avoid obstruction.
Note that due to the short wavelength at Ka band and the
narrow beam width of the ADU even a 6mm steel wire
placed within 50 m inside the beam can causes signal
degradation.
Figure 3-1: Signal degradation because of obstructing objects
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