FISH 4350 / 4380
Installation and Operation Manual
17
NAVMAN
Transducers Installation Guide
).
•
If the boat is anchored then
Þ
sh will tend to
show on the display as horizontal lines as
they swim into and out of the transducer
sonar beam. Slow speeds in deeper water
give the best
Þ
sh arch returns.
•
Range is important. It will be much easier
to see
Þ
sh arches when using zoom mode
to concentrate on a particular section of
water, rather than just displaying everything
from the surface to the bottom. Zooming
increases screen resolution up to 100 times.
•
It is dif
Þ
cult to get
Þ
sh arches in shallow
water as the transducer sonar beam is very
narrow near the surface and
Þ
sh do not stay
within the beam long enough to display an
arch. Several
Þ
sh in shallow water tend to
display as randomly stacked blocks of pixels.
• Wave motion may result in distorted fish
arches.
Fish arches
In good conditions and with Fish symbols
Off
,
a
Þ
sh passing through the cone-shaped ultra-
sonic pulse is displayed as a
Þ
sh arch.
A
Þ
sh arch occurs when a
Þ
sh enters the weak
edge of the sonar cone, generating a weak echo
that is displayed as the
Þ
rst pixel of the
Þ
sh arch.
As the
Þ
sh moves closer to the middle of the
cone, the distance between the transducer and
the
Þ
sh reduces and the echo is displayed at
progressively shallower depths, producing the
start of an arch. When the
Þ
sh passes directly be-
neath the middle of the cone, the echo becomes
strongest and thickest. As the
Þ
sh passes out of
the middle of the cone the reverse happens with
a progressively weaker and deeper echo.
There are many reasons why
Þ
sh arches may
not be seen. For example:
•
Poor transducer installation (see
Transom
4-3 Gain
Gain (sensitivity) controls the amount of detail
displayed on the FISH 4350 and FISH 4380.
Understanding how to set suitable Gain settings
is important for optimum performance.
The Navman
Þ
sh
Þ
nder has two gain modes,
Auto Gain and Manual Gain. Normally the
best results are obtained in Manual Gain, but
practice and experience are required to obtain
the optimum settings for different conditions.
Therefore, the use of Auto Gain is strongly
recommended when learning to use the
Þ
sh
Þ
nder or when travelling at speed.
•
In Auto Gain, the gain adjusts
automatically to compensate for water
depth and clarity.
•
In Manual Gain, the gain can be adjusted
by the user to compensate for water
depth and clarity.
High Gain settings may amplify the normal back-
ground noise until it appears as random pixels.
Changing between Auto and Manual
To change between Auto Gain and Manual
Gain:
1. From any Sonar display, press .
2. Use the cursor key to select
Auto
or
Manual
.
Adjusting Gain settings
1. From any Sonar display, press .
2. Use the or cursor keys to change the
gain.
Unwanted
signal
Gain
Threshold
line
Gain line
Note:
The Gain mode
automatically changes
to Manual Gain if the
gain setting is adjusted
by the user.
Obtaining the best
results
To obtain the best
detection capability for
both fish and bottom
we recommend the
user adjusts the gain in the A-Scope display
until the threshold line is just to the right of the
unwanted noise:
