Northstar
FISH 457/467
Installation and Operation Manual
16
3 Sonar fishfinding: Introduction
Sonar functions require the optional sonar
transducer to be installed and set up.
This section explains how to interpret the sonar
displays, when and why to use the different
frequencies and how fish are detected and
displayed.
It also describes Gain and Range and shows
examples of some of the different sonar displays.
3-1 Using the 457/467
The 457/467 uses a sonar transducer attached to
the hull. The transducer generates an ultrasonic
pulse (sound that is above the hearing range
of the human ear), which travels down towards
the bottom at a speed of about 4800 ft/sec
(1463 m/sec), spreading out into a cone shape.
When the pulse meets an object, such as a fish
or the bottom, it is partly reflected back up
towards the boat as an echo. The depth of the
object or bottom is calculated by the 457/467 by
measuring the time taken between sending a
pulse and receiving the echo. When an echo has
been returned, the next pulse is sent.
The 457/467 converts each echo into an
electronic signal, displayed as a vertical line of
pixels. The most recent echo appears on the
extreme right of the display, with the older
echoes being scrolled towards the left, eventually
disappearing off the display.
The scroll speed depends upon the water depth
and scroll speed setting. See sections 8-2 and
section 3-2, for more information.
The appearance of echoes displayed are affected
by:
•
the 457/467 settings (see sections 8-2, 3-5 and
3-6)
•
echoes (different fish types, different bottom
types, wrecks and seaweed; see section 3-2)
•
noise (water clarity and bubbles; see section
3-2).
Cruising, Fishing and Manual Modes
The 457/467 has three sonar operating modes:
•
Cruising mode
: Use this when on the move.
The 457/467 automatically adjusts its settings
to compensate for water clarity and to display
the bottom.
•
Fishing mode
: Use this when fishing. The
457/467 automatically adjusts its settings
to compensate for water clarity and to best
display fish, the bottom and other details.
•
Manual mode
: Use this to fine-tune the
457/467 settings by hand. Best results are
often achieved in manual mode, but practice
and experience are required to obtain the
optimum settings for different conditions.
For more information about modes, see sections
3-5 and 3-6.
Use the automatic Cruising or Fishing modes
when learning to use the 457/467 or when
travelling at speed.
!
WARNING
