SENSITIVITY Big rocks or stumps on a smooth bottom send back
signals above the
The sensitivity key
on the X-55A controls the ability of the unit to pick up
echoes. A low sensitivity level excludes much of the bottom information,
fish signals, and other
target
information. High sensitivity levels enables
you
to see this
detail, but itcan also clutterthe
screen with
many
undesired
signals. Typically, the best
sensitivity level shows a good solid bottom
signal with Grayline and some surface clutter.
When the X-55A
is in the Automatic mode,
the
sensitivity is
automatically
adjusted to keep
a solid bottom
signal displayed, plus
a little more. This
gives
it the
capability
to show fish and other detail.
However,
situations occur where it becomes necessary to increase or
decreasethe
sensitivity.
This
typically happenswhen you
wish to see more
detail,
so an increase in sensitivity is indicated. The
procedure
to
adjust
it
is the same whether the unit is
in
the
automatic or manual mode.
To
adjust
the
sensitivity, press the SENS key. The
sensitivity adjust menu
appears
at the bottom of the screen.
The
sensitivity
menu has left and right arrows, plus a horizontal bar graph.
The graph gives a visual indication of the sensitivity level. The number
above the INC arrow
also shows the
percentage of sensitivity in use.
To increase the sensitivity level, press
the right
arrow key. As
you press
the
key, the menu's bar graph will grow wider and the
percentage will
increase in value. You can also see the difference on the chart record as
it scrolls. When the sensitivity is at the desired level, release the
key.
To decrease
the sensitivity level, press the key adjacent to the left arrow.
The bar
graph and
percentage
will decrease. When the
sensitivity is at the
desired level, release the key.
When you reach either the
maximum or minimum limit, a
tone sounds.
bottom
level
signal. The
height
of the
signal depends on
thetarget's height.
Asyou
pass
overa
post,
it should be
clearlyvisible
as a short
lineextending
above the bottom
signal.
Asteep slope
returns a wide
signal,
the
steeperthewider. Signals returned
from a high underwater cliff are
usually the widest of all.
WATER TEMPERATURE AND THERMOCLINES
Water
temperature has an
important-if not
controlling-influence upon
the
activities of all fish. Fish are cold blooded and
their bodies are always
the
temperature of the surrounding water. During the winter, colder water
slows down their metabolism. At this time,
they need about a fourth as
much food as they
consume in the summer.
Most
fish don't
spawn
unlessthe
watertemperature
is within rathernarrow
limits. A surface temperature meter helps identify
the desired surface
water
spawning temperatures for various
species. Trout
can't survive in
streams
that get
too warm. Bass and other
fish eventually die out when
stocked in lakes that remain too cold during the
summer. While some fish
have a
widertemperature tolerance than
others, each has a certain
range
within
which it tries to
stay. Schooling fish suspended
over
deep water lie
at the level that
provides this
temperature. We assume
they
are the most
comfortable here.
Thetemperature
of water in the lake is seldom constantfrom topto
bottom.
(See
the
picture
on the next
page.) Layers of
different temperatures
form,
and the
junction of a warm and cool layer
of water is
called a thermocline.
The depth and thickness of the thermocline can vary
with the season or
time
of
day.
In deep lakes there
may
be two
or more at different depths.
Thermoclines are
important to fishermen because they
are areas where
fish are active. Many times bait fish will be above the thermocline while
larger game fish will suspend in or
just
below it.
The X-55A can detectthis invisible layer in the
water, butthe
sensitivitywill
probably
have to be turned
up
to see it.
When the Fish l.D. mode is
off,
the depth of the water will affect the size
and shape of the fish arch due to the cone angle diameter. For
example,
if the cone
passes over a fish in shallow water, the
signal displayed
on the
X-55A
may
not arch at all. This is due to the narrow cone diameter and the
resolution limitations of the
display.
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