Furuno 821 Operator's Manual page 41

Mounting procedure for MODEL 821
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.
Spring
washer
Figure 5-2 Antenna unit (MODEL 821),
showing location of mounting hardware
2) Unfasten the fixing bolts for the radome
base.
Fixing
bolt
Figure 5-3 Antenna unit (MODEL 821),
showing location of fixing bolts
30
Mounting platform
3) Prepare a platform of 5 to 10mm in
Flat
washer
M10 x 20
hex head bolt
4) Find the cable entry on the radome base.
Rubber
washer
thickness for the antenna unit. (For sail-
boats, an optional mounting bracket
which can be fixed to a mast is avail-
able. See page 35 for details.)
The mounting surface must be parallel
with the waterline and provided with five
holes whose dimensions are shown in the
outline drawing at the back of the
manual. Four 10mm holes for fixing, 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.
Position the radome base so the cable
entry faces the stern direction. (This
alignment must be as accurate as pos-
sible.)