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4. The boat must be
moving
at
aslowtrolling
speed
to seefish arches. If the boat
Is
motionless,
fish
stay
in the
cone, showing
on the
display
as
straight
horizontal
lines.
ELECTRICAL NOISE
A
major
cause of sonar
problems
is electrical noise. This
usually appears
on the
sonar's
display
as random
patterns
of dots or lines. In severe
cases,
it can
completely
cover the screen with black
dots,
or cause the unit
operate
erraticly,
or not at all.
To eliminate or minimize the effects of electrical
noise,
first
try
to determine the
cause. With the boat at rest in the
water,
the first
thing you
should do is
turn all
electrical
equipment
on the boat off. Make certain the
engine
is
off,
also. Turn
yourX-25
on,
then turn off ASP
(Advanced Signal Processing).
There should
be
a
steady
bottom
signal
on the
display.
Now turn on each
piece
of electrical
equipment
on the boat and view the effect on the sonar's
display.
For
example,
turn on the
bilge pump
and viewthe
sonardisplayfor
noise. If no noise is
present,
turn the
pump
off,
then turn on the VHF radio
and transmit.
Keep doing
this until
all electrical
equipment
has been turned
on,
their effect on the sonar
display
noted,
then turned off.
If
you
find noise interference from an electrical
instrument,
trolling
motor,
pump,
or
radio, try
to isolate the
problem.
You can
usually
re-route the sonar unit's
power
cable and transducer cable
away
from the
wiring
that
is
causing
the
interference. VHF radio antenna cables radiate noise when
transmitting,
so be
certain to
keep
the sonar's wires
away
from it. You
may
need to route the sonar
unit's
powercable
directly
to the
batteryto
isolate it from
otherwiring
on the
boat.
If no noise
displays
on the sonar unit from electrical
equipment,
then make
certain
everything except
the sonar unit is turned
off,
then start the
engine.
Increase the RPM with the
gearshift
in neutral. If noise
appears
on the
display,
the
problem
could be one of three
things; spark plugs,
alternator,
ortachometer
wiring. Try using resistorspark plugs,
alternatorf
lIters,
or
routing
the sonar unit's
power
cable
away
from
engine wiring. Again, routing
the
power
cable
directly
to
the
battery helps
eliminate noise
problems.
Make certain to use the in-line fuse
supplied
with the unit when
wiring
the
power
cable to the
battery.
When no noise
appears
on the sonar unit after all of the above tests,
then the
noise source is
probably
cavitation,
Many
novices or
persons
with limited
experience
make
hasty
sonar installations which function
perfectly
in shallow
water,
orwhen the boat is at rest. In
nearly
all
cases,
the cause of the malfunction
will be the location and/or
angle
of the transducer.
The face of the transducer
must be
placed
in a location that has a smooth flow of water at
all boat
speeds.
Read
your
transducer owners manual for the best
mounting position.
25
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