Specifications

1. INTRODUCTION
The
Eagle
Z-15 is a
highly
sophisticated recording depth
sounder. Thanks to a micro-com-
puter,
the Z-15 can 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
Eagle
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 attached 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
Z-15
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
Z-15,
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 transmitted and it is easier for
the receiver to detect it.
For this
reason,
the micro-com-
puter
in the Z-15
automatically
increases
the
initial
pulse length
of
the unit as
deeper
lower limits are
set
by
the
opQrator. (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
130
160
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
would
be 260 is. If
the LOWER LIMIT is set to 390
feet,
the initial transmit
pulse
would
be 390
ps. 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
800
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
separation
or
resolution is
degraded. However,
if
the
pulse
width
is
decreased,
res-
olution becomes much better.
The Z-15
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 ihitial
transmitter
pulse
length
can
be set from 30
ps
to
200Q s
by entering
it on the
key-
board.
By setting
the initial trans-
mitter
pulse
width to 100
ps,
a
three inch resolution is
obtained,
50 is is
equivalent
to an inch and
a
half,
and 30
is 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 initial
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
20
30
40-200
f
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