NorthStar Navigation NorthStar 8000i - Manual (Page 116)

116 Northstar 8000i Operation Manual
5. Select OK to confirm the new setting. The new setting is applied
immediately and stays until you change it again.
6. If you want to adjust the gain for the other frequency, repeat Steps 2
through 5.
7. When you are finished, select Return.
NOTE: If you're using fishing or cruising mode and adjust the gain yourself, the
sounder automatically changes to manual mode.
18.3 What is the gain threshold?
You can use the gain threshold to define the weakest echo (the minimum
amplitude) that you want to show on your Sounder screen.
Each amplitude is associated with a particular color, so the gain threshold also
controls the range of colors displayed.
If you set the gain threshold:
•
too low, the maximum amount of colors are shown and background noise
generated by factors such as planation and particulate matter may be shown
as confusing random pixels.
•
too high, there won't be enough useful detail about the bottom and echoes
from some objects won't be shown.
Ideally, you should set the gain threshold at a level just above the background
noise.
If you're in fishing mode or cruising mode the sounder adjusts the gain threshold
automatically.
18.4 Change the gain threshold
The gain threshold line is shown on the advanced A-scope screen as a thin white
vertical line. You may find it useful to view this screen while you adjust the gain
threshold.
You can adjust the gain threshold for the 50 kHz and 200 kHz independently of
each other. The default for both is 0.
To change the gain threshold:
1. Display the Sounder screen and the control panel. If you can't see the
Gain and Filters button, select Return.
2. Select
Gain and Filters, then select one of:
ƒ
200 kHz Threshold if you want to adjust the gain threshold
for the 200 kHz frequency or for a Mixed frequency.
ƒ
50 kHz Threshold if you want to adjust the gain threshold for
the 200 kHz frequency
3. A slider box appears. The current setting is shown as a line within a
solid box of color and as a percentage.
4. Drag the line, or use the rotary knob, to change the gain threshold.
5. Select OK to confirm the new setting. The new setting is applied
immediately and stays until you change it again.