Navman 8084, Инструкция по установке и эксплуатации

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NAVMAN 8120/8084 Installation and Operation Manual 37
CAUTION
Planing hulls at speed produce air bubbles
and turbulent water that bombard the
transducer. The resulting ultrasonic noise
may be picked up by the transducer and
obscure the real echoes.
The scroll speed can be set by the user to
display either a longer history with less fish
information or a shorter history with more
fish details (see section 19-3).
If the boat is anchored, the echoes all come
from the same area of bottom. This produces
a flat bottom trace on the window.
The screen shot shows a typical sonar
window with the Fish symbols turned
Off
.
The sonar pulse generated by the Instrument
transducer travels down through the water,
spreading outwards in a cone shape. The
cone width is dependent upon the frequency
of the pulse; at 50 kHz it is approximately 45°,
and at 200 kHz it is approximately 11°.
The differences in the cone width affect what
is displayed. (See section 9-3)
Strength of echoes
The colors indicate differences in the strength
of the echo. The strength varies with several
factors, such as the:
• Size of the fish, school of fish or other
object.
• Depth of the fish or object.
• Location of the fish or object. (The area
covered by the ultrasonic pulse is a rough
cone shape and the echoes are strongest
in the middle.)
• Clarity of water. Particles or air in the water
reduce the strength of the echo.
• Composition or density of the object or
bottom.
Bottom types
Mud, weed and sandy bottoms tend to
weaken and scatter the sonar pulse, resulting
in a weak echo. Hard, rocky or coral bottoms
reflect the pulse, resulting in a strong echo.
Frequency and cone width
Water Depth ft/m Cone width at 50 kHz Cone width at 200 kHz
45˚ cone 11˚ cone