Sea Tel 5012-91, Installation Manual, Page: 15 / 138

Site Survey 5012-91 Installation Manual
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foot rung should be added. Additional rungs should be added for every 0.3 meter (12 inches) of
pedestal height above the ship’s structure.
9. For an ADE mounted greater than 3 meters (9 feet) above the ship’s structure, a fully enclosing cage
should be included in way of the access ladder, starting 2.3 meters (7 feet) above the ship’s
structure.
2.4. Mounting Height
The higher up you mount the antenna above the pivot point of the ship the higher the tangential acceleration (g-
force) exerted on the antenna will be (see chart below).
When the g-force exerted on the antenna is low, antenna stabilization and overall performance are not affected.
If the g-force exerted on the antenna is high enough (> 1 G), antenna stabilization and overall performance are
affected.
If the g-force exerted on the antenna is excessive (1-2 Gs), the antenna does not maintain stabilization and may be
physically damaged by the g-force.
2.5. Mast Configurations
Sea Tel recommends mounting the ADE in a location that has both a clear line-of-sight to the target satellites in all
potential azimuth/elevation ranges and sufficient support against vibration excitement. If possible, mounting the ADE
pedestal directly to ship deckhouse structures or other box stiffened structures is preferred. However, in many cases,
this imposes limits on the antenna system’s clear line-of-sight.
Often the solution for providing the full azimuth/elevation range the antenna needs is to mount the ADE on the ship’s
mast. Unfortunately, masts do not consider equipment masses in design and often have harmonic frequencies of their
own.
There are many designs of masts used on ships – masts are nearly as unique in design as the ship is – but the designs
often fall into a few categories. These categories can be addressed in terms of typical responses and problems with
regards to vibration and mounting of ADE. The most common categories of masts are: