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
PDF compression, OCR, web-optimization with CVISION's PdfCompressor