Northstar
FISH 457/467
Installation and Operation Manual
24
3-6 Gain and threshold
Gain and threshold settings control the amount
of detail displayed on a sonar display:
Gain
: The gain of the sonar receiver. The gain
should be high to display good detail, but if the
gain is too high then information from the strong
bottom signal is lost and false echoes might be
displayed.
Threshold
: Return echoes less than the
threshold are ignored. The threshold should be
as low as possible, but if the threshold is too low,
unwanted noise will be displayed. Threshold is
set as a percentage of gain. For example, if the
threshold is 50%, then return echoes less than
50% of the maximum signal are ignored.
The gain window
To display or change the current settings for gain,
select a sonar display and press
. Select
Threshold
to display the thresholds. There
are separate gain and threshold settings for each
sonar frequency, 50 kHz and 200 kHz.
This display is called the gain window.
Changing mode
The 457/467 has three operating modes. In
Cruising and Fishing modes, the 457/467
automatically adjusts gain and threshold for good
performance. In manual mode, you can hand
adjust the settings.
To change the mode from the Gain window,
Select
Mode
and then select
Fishing
,
Cruising
or
Manual
. When you select
Manual
, the 457/467 reverts to your last manual
settings.
Changing gain and threshold
1
In the Gain window, press
or
to select
the setting to adjust.
2 Press or
adjust the setting. The 457/467
changes to Manual mode.
Tip
: Use the A-scope display to help set gain
or threshold manually (see section 4-5).
