Navman 8084, Инструкция по установке и эксплуатации

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NAVMAN 8120/8084 Installation and Operation Manual 38
Shadows
Shadows are created around areas where
the ultrasonic beam cannot ‘see’. These
areas include hollows on the bottom or
beside rocks and ledges, where the strong
echoes returned off the rocks obscure the
weak echoes of the fish and may also create
a double bottom trace. See following for
Sonar window of same area Example of shadows
A Fish is visible on the window
B Fish is hidden by the strong echoes off the
bottom and is not shown on the window
9-3 Single and Dual frequency fishfinding
When to use 200 kHz
The 200 kHz frequency is especially suitable
for use in shallow and medium depth water,
typically less than 500 ft (150 m) and while
running at speed.
At 200 kHz, the narrow cone reduces any
noise caused by air bubbles.
Sonar frequencies
The Instrument has two sonar frequencies,
200 kHz and 50 kHz. To select the sonar
frequency to use:
1 Go to a sonar window (see section 9).
2 Press
MENU
, select
Frequency
and select
200 kHz
,
50 kHz
, or
Mixed
.
an example of the sonar window in such
an environment. A double bottom trace is
shown on the window.
When looking for fish with the wide angled
50 kHz frequency, be aware of increased
shadows. Use the high frequency 200 kHz
in areas that have rocks and ledges because
this frequency reduces the shadow effect
considerably.
A
B
A
A
B
A