NorthStar Navigation NorthStar 8000i - Manual (Page 101)

Northstar 8000i Operation Manual 101
15 The sounder
The sounder is a high quality, dual frequency fishfinder. It can help you to find fish,
locate underwater features such as wrecks and reefs, and identify favorite fishing
spots from the bottom profile.
The dual frequency ability enables the sounder to operate in shallow and deep
water to a depth of about 3300 ft (1000 m) depending upon the water clarity, the
frequency chosen, and the type of transducer fitted to your vessel.
The sounder is supplied with default settings, but you can customize many of
these to suit your own preferences.
Depth soundings should be used only for navigation. Never use a depth sounding to
gauge depth, range or other conditions for swimming or diving.
15.1 How the sounder works
The transducer attached to the hull produces an ultrasonic pulse (sound that is
outside the hearing range of the human ear). This travels down towards the
bottom at about 4800 ft/sec (1463 m/sec) spreading outwards into a rough cone
shape.
When the pulse hits an object, such as a fish or seaweed, it's partly reflected back
up to your vessel as an echo. The sounder calculates the depth of the object or the
bottom by measuring the time taken between sending the pulse and receiving
the echo.
The Sounder screen shows each echo as a vertical line of pixels. The most recent
echo is on the extreme right of the display screen, with the older echoes being
scrolled towards the left and eventually disappearing. This type of display is
known as the "history".
Many variable factors, such as the clarity of the water, can affect the appearance of
the Sounder screen.
16 Use the sounder
The sounder provides a variety of operating modes, screen options, and settings
that you can choose to suit your level of experience, and the current environment
and activity.
This section explains the Sounder screen and status bar, and the changes you can
make.
You can show or hide the:
•
depth line
•
depth value
•
A-Scope