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Recording
individual
fish with an
"arched"
signature
can
usually
be
accomplished
at
trolling speed
with the
Sensitivity
knob at the ¾
point,
or
higher.
Refer to
the
section 'Arched
Signatures"
for
more information about
this
impor-
tant
function of the recorder.
12.0
244
/
b'240
36,0
360
480
FIGURE
6
CLEAR
ENTRY
The CLEAR ENTRY
key
is used
when a mistake has been made
when
entering
a command to the
unit.
If,
for
example, you
wish to
set the lower
depth
limit to 500
feet,
and
by accident,
you press
509. BEFORE
you press
the
LOWER LIMIT
key, you
can
press
the CLEAR ENTRY
key
which
erases the
mistake,
and
allows
you
to re-enter the
correct
command.
DISCRIMINATION
Noise
pulses
are the
largest
complaint
most often received
about sonar
units. Lowrance has
had the
patented
Suppression
system
for
many years
which is
quite
effective at
eliminating
noise
from the
display.
The
only
draw-
back to the
Suppression
system
is
that it increases the
transmitter's
pulse length
which
decreases res-
olution and causes
targets
that are
close
together
to
merge
into one
"blob" instead of two
distinct
images.
Discrimination is a
program
installed in the X-16's micro-
processor
that enables it to
process
the
output
from the
receiver,
determine which
signals
are
noise and eliminate
them,
then
print only
the
legitimate
echoes.
Using
this
concept,
the transmit-
ted
pulse
does not have to be
increased,
therefore records with
high
resolution and
high
noise
immunity
can be achieved.
Discrimination is
interlaced with
Suppression, however,
and
some
suppression
is used
when
higher
levels of Discrimination are
chosen. For a
complete explana-
tion of
Suppression
and
Discrimination,
see the Advanced
Operation
section entitled
"Sup-
pression".
There are five levels of
Discrimination that can be
used.
(0)
is the lowest level whereas the
highest
value
(4)
is the
stron9est
level and should be used
only
when
severe noise is
present.
Another
advantage
of Discrimi-
nation is its
ability
to filter out
interference from other
depth
sounders. This allows
the simul-
taneous
operation
of a
digital
depth
sounder and the
X-16. Turn
both units on. If
interference from
Suppressor
level
by
using
the
Suppressor
control at
any
level
above 3. The
Suppressor
control
will
override the automatic
selec-
tion
that Discrimination chose. If a
suppression
level
greater
than 0 is
selected
by
the
operator,
then the
X-16 will
print
an
"F' after the
Discrimination level, For
example
if
the Discrimination
level is 1 and
the
Suppressor
level is
set
(or
"fixed")
to
3,
then the
X-16 will
print
"D
=
1 F'. This is a
reminder
that
some level of
suppression
is
in use.
(See Figure 43.)
-
—
lab
- 12.0
24.0
-
-
84,0
36.0
4S.0—
60,0FT——B1F--L0URAr1CE
60
OFT-j
FIGURE 43
PULSE
In the
Suppressor
section of this
manual,
we
explained
the relation-
ship
between
pulse
length
and
target separation.
As
pulse length
increases,
target separation,
As
pulse
length
increases,
target sep-
aration or
resolution is
degraded
but
deep
water
penetration
improves. However,
if the
pulse
width is
decreased,
resolution
becomes much better. The
X-16
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
ps
to
1700
ps by entering
it on the
keyboard. By setting
the initial
transmitter
pulse
with to 100
jis,
a
three inch resolution is
obtained,
50
ps equivalent
to an inch and a
half,
and 30
ps
initial transmit
pulse
length
is
equal
to one inch
resolution! No other
graph
recorder in the market
today
can
give you
this feature. After
setting
the initial transmitter
pulse length,
the Discrimination
function can be
used to eliminate noise and
still
have
good
resolution.
The X-16 will
display
the
initial
transmitter
pulse length
at the
bottom of the
paper
when
you
over-ride the
micro-computer.
To
distinguish
the initial transmitter
pulse
from the other information
printed
on the
paper,
the
graph
will
print
P=100
(if
the
pulse
is set
to 100
micro-seconds.)
A 50
ps
initial
pulse length
would be dis-
played
as P=50.
(See Figure 44.)
NOTE: If a
pulse
length
110
micro-seconds or
less is chosen
by
the
operator,
the
Suppressor
is
disabled.
Also,
less than max-
imum
power
is transmitted
when
the
pulse length
is
less than 100
micro-seconds.
To set the initial transmitter
pulse length, simply press
on the
FIGURE 5 SENSITIVITY: TOO LOW
0.0
0
-'
L\ 4
SENSITIVITY: PROPER SETTING
Figure
44
6
23
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