Northstar
Explorer 660
Installation and Operation Manual
37
8-5 Gain, threshold and range
The Explorer has three settings that affect the
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. There
is a separate gain setting for each sonar
frequency, 50 kHz and 200 kHz.
•
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. There is a separate threshold
setting for each sonar frequency, 50 kHz and
200 kHz.
To display the current settings for gain and
threshold, select a sonar display and press
ENTER:
8-5-1 Changing between automatic and
manual modes
Select a sonar display before changing mode (see
section 9).
a Using an automatic mode
Press
GOTO/AUTO
and select Cruise or
Fishing (see section 8-1). The Explorer
660 will adjust gain, threshold and range
automatically.
b Using
manual
mode
Press
GOTO/AUTO
and select Manual. The
Explorer 660 reverts to your last manual
settings (see section 8-1).
c
Adjusting gain or threshold manually
1
Press
ENTER
to display the gain window:
2 Press or
to select the setting
to adjust.
3 Press or
adjust the setting.
If the Explorer 660 is in Cruise or Fishing
modes, it will stop adjusting gain and
threshold automatically but will continue to
adjust range automatically.
Tip
: Use the A-scope display to help
set gain or threshold manually (see section
8-5-2).
To revert to automatic:
•
Either
press
GOTO/AUTO
and select Cruise
or Fishing.
•
Or
press
ENTER
to display the gain window,
select
Manual
and press
.
The Explorer 660 will not adjust threshold
automatically; if gain is manual it will stay
manual.
d Adjusting range manually
•
Either
press or
to increase or
decrease range.
•
Or
press
MENU
, select
Range
and select
Manual
. Range does not change.
If the Explorer 660 is in Cruise or Fishing
modes, it will stop adjusting range
automatically but will continue to adjust gain
and threshold automatically.
This display is called the gain window.
•
Range
: The vertical depth covered by a
Explorer 660 sonar display. For example, if the
range is 100 m, then the sonar display shows
depths between 0 and 100 m. The range is
displayed at the bottom, right corner of a
sonar display.
If the bottom is deeper than the specified
depth range, it will not be shown on
the display.
The Explorer 660 has three operating modes,
Cruise, Fishing and Manual (see section 8-1).
In Cruise and Fishing modes, the Explorer 660
automatically adjusts gain and threshold for
good performance and adjusts range to always
show the bottom. In manual mode, you can hand
adjust the settings.
