1. INTRODUCTION
The Lowrance X-1SB is a highly
sophisticated recording depth
sounder. Thanks to a micro-com-
puter, the X-l5Bcan do more than
any other sonar unit in its price
range plus many that cost much
more. Thanks to a waterproof
key-
board, full control of the system
is
at your
fingertips
to meet the
changing demands of varying bot-
tom conditions, water
depth, and
boat speed. You can select the
unit's
sensitivity, suppression level,
upper
and lower
depth range, pa-
per speed, GRAYLINE, and many
more features. The patented
Lowrance variable suppression
system
combined with the new
Discrimination feature
not only fil-
ters out false signals without dis-
torting
the real ones, but is
synchronized with the GRAYLINE
function to provide clear signals
under all conditions.
2. HOW IT WORKS
When the Unit is turned on, an
electronically regulated motor
drives
a lightweight belt located at
the right edge of the recording pa-
per. The
stylus is éttached to this
belt:
When the stylus is at the top
of the paper
a small mark is
made. This is called the zero
mark, and represents the surface
of the water. The stylus
continues
to move down the edge of the
paper
while the sound
pulse is
traveling through the water, and
when an echo is detected, the sty-
lus makes another mark on the
paper. The depth of the object
which reflected the echO can be
read in feet by comparing its loca-
tion on the paper
to the depth
scale printed on the paper.
The paper speed is controlled
by a variable speed motor. During
one revolution of the stylus belt, a
very
narrow mark will be made by
the flexible stylus, but the paper
will move a small amount before
the next revolution. Each mark will
blend into the one before so that a
composite "picture" of the target
will be made, one tiny mark at
a time.
Due to the many features
that
this unit has, this manual has the
operation section split into two
parts. The first section is entitled
"Basic Operation" and covers
everything that is absolutely
necessary to use the X-15B in a
wide variety
of situations. It will tell
you how to use the basic controls
- Sensitivity, Suppression, Paper
Speed, GRAYLINE, Range, plus a
few special functions. This section
will be adequate for most situa-
tions. However, once you have
mastered the basic operation of
the X-15B, you may
wish to try
some of the features
described in
the Suppressor control turned
down to minimum when looking
for fish.
However, it is helpful sometimes
to have longer pulse
width when
resolution is not a concern. When
using a
sonar in deeper water, it is
easier for the unit to detect a long-
er pulse coming back
from the
bottom or from
fish. This is called
"Probability of Echo
Detection".
The probability of the unit being
able to detect an echo returning
from deep water is diminished be-
cause the further the sound pulse
has to travel, the weaker it be-
comes. By broadening the pulse
length, in essence, a larger signal
is tranmitted and it is easier for
the repeiver to detect it.
For this reason, the micro-com-
puter in the X-15B automatically
increases the initial pulse length of
the unit as deeper
lower limits are
set by the operator. (Note: Initial
pulse
length is the pulse length of
the unit when the
Suppressor con-
trol is turned to minimum.)
INITIAL
TRANSMIT
PULSE
WIDTH
(micro-seconds)
110
20 •130
30 160.
40-200 200
From 210 feet to 600 feet, the
initial pulse length increases at the
same rate as the depth. For ex-
ample, with the LOWER LIMIT set
to 260 feet, the initial transmit
pulse length ouId be 26Oxs. If
the LQWER LIMIT is set to 390
feet, the initial transmit
pulse
would be 390 Finally, from
600 feet and below, the initial
pulse length remains at 600
micro-seconds.
The
transmit
pulse length can
be increased from the initial point
at any
time by rotating the Sup-
pressor control clockwise. The
maximum amount of pulse length
added to the
initial transmitter
pulse length is approximately aoo
micro-seconds. In other
words, if
the LOWER LIMIT is set to 420
feet, and the Suppressor control is
rotated to the maximum position,
the transmitter pulse length would
be 1220 micro-seconds. (420
initial + 800 = 1220.)
Earlier, we talked
about the rela-
tionship
between pulse length and
target separation. As pulse length
increases, target
separaflon or
resolution is degraded. However, if
the pulse width is decreased, res-
olution becomes much better.
The
X-159 allows you to take
advantage of this fact by making it
possible to override the initial
transmitter pulse
length setting
from
what the micro-computer
selects according to the Lower
Limit.
The initial transmitter pulse
length can be set from
30 ts to
2000 p.s by entering it on the key-
board. By setting the initial trans-
mitter pulse width to 100 p.5, a
three inch resolution is obtained,
50 p.s is equivalent to an inch and
a half, and 30 p.s initial transmit
pulse
length is equal to one inch
resolution! No other
graph re-
corder in the market today
can
give you this
feature. After
setting
the initia( transmitter pulse length,
the suppressor control can still be
used to cancel out noise by in-
creasing the pulse length or the
Discrimination function described
below can be used to eliminate
noise and still have good
Figure 1
LOWER
LIMIT
(feet)
10
-
r— .--• _—
PULLEY
TI] 1 DRIVE
L: +-1STYLUS
• i DRIVE
BELT
STYLUS
GRAPH
PAPER
PAPER
TRAVEL -4-—PuLLEV
2 19
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