Mounting procedure for MODEL 841
Removing packing materials
1)Open the radome cover carefully. Re- move mounting hardware at the bottom of the radome base assembly; four each of M10 bolts, spring washers and flat washers. This hardware may be dis- carded; do not use them to fix the an- tenna unit to the mounting platform.
Flat
washer
Spring 
washer 
M10 x 20 hex head bolt
Figure 5-7 Antenna unit (MODEL 841), showing location of mounting hardware
2)Unfasten the four fixing bolts securing the radome cover to the radome base. Lift radome carefully to remove the antenna radiator packing materials.
Figure 5-8 Antenna unit (MODEL 841),
showing location of fixing bolts
Mounting platform
3)Prepare and fasten a platform of 5 to 10mm in thickness to the mounting lo- cation. (For sailboats, an optional mount- ing bracket which can be fixed to a mast is available. See page 35 for details.)
The mounting surface must be parallel with the waterline and provided with six holes whose dimensions are shown in the outline drawing at the back of the manual; four 12mm holes for fixing, and one 27 mm hole for cable entry, and one 20mm hole for the vent tube.
There is a cable entry (cable gland) out- side the antenna unit which should face the stern direction. The unit is adjusted so a target echo returned from the bow direction will be shown on the zero de- gree (heading marker) position on the screen. When drilling holes, be sure they are parallel with the fore and aft line.
Vent tube
Moisture can condense inside the ra- dome, causing corrosion, if a means is not provided to keep moisture out of the radome. A vent tube fitted on the base of the radome allows the radome to "breathe" while not allowing entry of water from outside into the radome. Be sure the tube is kept free of foreign ma- terials and is not pinched or kinked. The vent tube extends downward by 27mm from the radome base. Ensure the vent tube extends downward before mount- ing the radome base.
4)Find the cable entry on the radome base. Position the radome base so the vent tube faces the stern direction. (This alignment must be as accurate as possible.)
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