Navman FISH 4500/4600 - Manual (Page 20)

4-4 Gain
Gain (sensitivity) controls the amount of detail
displayed on the FISH 4500/4600. Understand-
ing how to set suitable Gain settings is important
for optimum performance.
The Navman fishfinder 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 opti-
mum settings for different conditions. Therefore,
the use of Auto Gain is strongly recommended
when learning to use the fishfinder or when
travelling at speed.
• In Auto Gain, the gain adjusts automati-
cally 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 ENT.
2. Use the or cursor keys to highlight
Auto or Manual, then use the or cur-
sor keys to select the required mode.
Adjusting Gain and Threshold settings
The gain settings and the threshold settings can
be adjusted independently for each frequency
(50kHz and 200 kHz).
Use threshold to eliminate colors in the sonar
display.
1. From any Sonar display, press ENT.
2. Use the or cursor keys to highlight the
desired setting, then use the or cursor
keys to change it.
Note: The Gain mode
automatically changes
to Manual Gain if the gain
or threshold settings are
adjusted by the user
Obtaining the best results
To obtain the best detection capability for both
fish and bottom we recommend the use of the
Sonar A-Scope display:
1. Set the threshold to 0%.
2. Adjust the gain until the threshold line is
just to the right of the unwanted noise.
Unwanted
signal
Gain Thresh-
old line
Gain line
FISH 4500/4600 Installation and Operation Manual 20 NAVMAN