Sea Tel 9711-44 KU-BAND TX/RX Installation And Operation Manual Download

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9711-44 Ku-Band TXRX

Site Survey

2-5

2.5.3.

Girder Masts

Girder masts are large platforms atop a pair of

columns. Just like girder constructions in buildings,
they are relatively stiff athwart ship – in their

primary axis – but less stiff longitudinally and

torsionally. An example of a girder mast is shown in

this drawing, with the preferred ADE mounting

outboard and above the radar directly on one of the

columns and alternate with the ADE centered on
the girder above the plane of the radar.
The greatest weakness of girder masts is in torsion –

where the girder beam twists about its vertical

centerline axis. As with all mast designs discussed so far, mounting the antenna in line with the vertical

support structure will reduce the vibration tendencies. Mounting the antenna directly above the girder

columns provides ample support to the antenna pedestal and locates the antenna weight where it will
influence the natural frequency of the mast the least.

2.5.4.

Truss Mast

Truss masts are a variant on the girder mast

concept. Rather than a pair of columns supporting a

girder beam, the construction is a framework of
tubular members supporting a platform on which

the antennae and other equipment are mounted. A

typical truss mast is shown in this photograph.
Like a girder mast, truss masts are especially stiff in

the athwart ship direction. Unlike a girder mast, the

truss can be made to be nearly as stiff in the
longitudinal direction. Truss masts are particularly

difficult to estimate the natural frequency – since a

correct modeling includes both the truss structure

of the supports and the plate/diaphragm structure

of the platform. In general, the following guidelines

apply when determining the adequate support for
mounting an antenna on a truss mast:

Antenna ADE pedestal gussets should align

with platform stiffeners which are at least

200 millimeters in depth and 10 millimeters in thickness.

When possible, the antenna ADE pedestal column should align with a vertical truss support.

For every 100 kilograms of ADE weight over 250 kilograms, the depth of the platform stiffeners
should be increased by 50 millimeters and thickness by 2 millimeters.

Sea Tel does not have a recommended arrangement for a truss mast – the variability of truss mast designs

means that each installation needs to be evaluated separately.

2.6.

Safe Access to the ADE

Safe access to the ADE should be provided. Provisions of the ship’s Safety Management System with regard to men

aloft should be reviewed and agreed with all personnel prior to the installation. Installations greater than 3 meters
above the deck (or where the access starts at a deck less than 1 meter in width) without cages around the access

ladder shall be provided with means to latch a safety harness to a fixed horizontal bar or ring.
The access hatch for the ADE shall be oriented aft, or inboard, when practical. In any case, the orientation of the ADE

access hatch shall comply with the SMS guidelines onboard the ship. Nets and other safety rigging under the ADE

during servicing should be rigged to catch falling tools, components or fasteners.

2.7.

Below Decks Equipment Location

The Antenna Control Unit, Terminal Mounting Strip and Base Modem Panel are all standard 19” rack mount, therefore,

preferred installation of these items is in such a rack. The ACU mounts from the front of the rack. The Terminal

Mounting Strip and Base Modem Panel mount on the rear of the rack.