Eagle Magna User manual

and
Magna Plus
INSTALLATION AND OPERATION
INSTRUCTIONS
LITHO IN U.S.A. 988-0106-42 EAGI F7jTM
Magna
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i-lowto ObtainService
We backyour investment in qualityproducts with quick, expertserviceand
genuine
Eagle replacement parts. Ifyou need serviceorrepairs, contactthe
authorized EagleService
Centernearest
you.Theenclosed ServiceCenterList
willhelpyou findthe
closest
repairfacility.
If
desired, you
cancontacttheFactory
CustomerService Center. Transportation expenses tousortotheAuthorized
Service Center areyour
responsability. Theproduct willbereturnedtoyou by
surfacecarrieratnocharge.
Factory Repair
Ifyourunitneeds
repair, andyouwishtowriteorsendaproduct tothefactory,
use thefollowing
address:
EAGLE ELECTRONICS
Alt: Service Department
12000 E Skelly Dr
Tulsa,OK74128-2486
You cancall orwritetoan authorized Eagle ServiceCenter or the Factory
CustomerService Department before sending your unit in for repair. A
technician
may
beabletosolvetheproblem
andsaveyou the inconvenienceof
returning yourunit.
Forthe Eagle factory
customerservice
department, call 1-918-234-1452.
When
sending
aproduct tothefactoryoraservice
center, werecommend you
dothefollowing:
1. Usethe originalbox andfiller materialthe productwaspacked in when
shipping yourproduct.
2. Always
insurethe parcelagainst damage
orloss
during shipment.
3. Forpropertesting, repair, andservice,
send abriefnotewith the product
describing
the problem. Be sure to includeyour name, return shipping
address, andadaytime
telephone number.
IMPORTANT:Be sure to include
proof of purchasewhen sending the
product
ifitisstill in warranty.
27
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4.Theboatmustbemoving at aslowtrolling
speedtoseefisharches.litheboat
ismotionless,fishstay
inthe
cone,
showing onthe display as
straight
horizontal
lines.
ELECTRICALNOISE
A
major
cause ofsonarproblems iselectrical noise. Thisusually appears
onthe
sonar's displayas random
patterns
ofdotsor lines. Inseverecases, Itcan
completely coverthescreen withblack
dots,
orcause the unit operate erraticly,
ornotatall.
Toeliminateorminimize theeffectsofelectrical noise, firsttry
todeterminethe
cause. Withtheboatatrestinthewater,thefirstthingyoushoulddoisturnall
electrical equipment
onthe boatoff. Make
certain theengine isoff,also. Turn
your
Magna
on,thenturn offASP(Advanced Signal Processing). Thereshould
bea
steady
bottom
signalon thedisplay.Nowturnoneachpieceofelectrical
equipment onthe boatandviewtheeffectonthesonar's
display.For
example,
turnonthe
bilgepumpandviewthesonardisplayfornoise.
Ifnonoiseispresent,
turnthepump off,thenturnontheVHFradioandtransmit.Keepdoing
thisuntil
allelectrical equipment
has beenturned
on, theireffecton thesonardisplay
noted, thenturned
off.
Ifyou
findnoiseinterferencefromanelectrical instrument, trolling motor, pump,
orradio,trytoisolate the problem. Youcanusuallyre-route thesonar unit's
powercableand transducercable awayfromthe wiring that is causing the
interference. VHFradioantenna
cables radiate noisewhen
transmitting, so
be
certain tokeep thesonar'swiresaway fromit. You
mayneedtoroutethesonar
unit's
powercable
directlyto
thebatterytoisolate
itfrom
otherwiring
ontheboat.
Ifno noisedisplayson thesonar unit fromelectrical equipment, then make
certain everything exdept the sonarunit isturnedoff, then startthe engine.
Increasethe RPMwiththegearshift
in neutral. Ifnoiseappears onthedisplay,
theproblem couldbeoneofthree
things;
sparkplugs, alternator, ortachometer
wiring. Tryusingresistorsparkplugs, alternatorfilters,
or
routingthesonarunit's
power
cable
away
from
enginewiring.Again,
routingthepower
cable
directly
to
thebatteryhelps
eliminatenoise
problems. Makecertain tousethein-line fuse
supplied withthe unitwhen
wiringthe power
cabletothebattery.
Whennonoise appears
onthesonarunitafterallofthe above tests,thenthe
noise sourceis probably cavitation. Many novices or persons with limited
experience makehastysonarinstallations whichfunction
perfectly
in shallow
water,orwhentheboatisatrest. In nearly
all
cases, thecauseofthemalfunction
will bethe location
and/or
angle
ofthetransducer. Thefaceofthetransducer
must beplaced
in alocationthathas asmooth flowofwater
atallboat speeds.
Read
yourtransducer
owners manualforthe bestmounting position.
26
TABLEOFCONTENTS
INTRODUCTION
INSTALLATION 1
POWER CONNECTIONS 2
SPEED/TEMPERATURESENSOR 3
KEYBOARDBASICS 4
DISPLAY 5
MENUS 5
OPERATION 6
AUTOMATIC 6
RANGE 6
ZOOM -AutomaticOperation 7
ZOOM -ManualOperation 8
SENSITIVITY 9
GRAYLINE® 9
FISH ID 10
cHART5PEED 11
DISPLAY MODE 12
ALARMS 14
FISH ALARM 14
DEPTH ALARM 15
LAMP 16
FEET/METER 16
DISPLAyCONTRAST 16
ASP (Advanced Signal Processing) 17
TRANSDUCERSANDCONE ANGLES 18
SIGNAL INTERPRETATION 19
FISH ARCHES 20
WATER TEMPERATUREANDTHERMOCLINES 21
SURVEYINGALAKE 23
BAITFISH 23
SONAR TROUBLESHOOTING 24
HOWTOOBTAIN SERVICE 27
Copyright © 1990, Eagle Electronics
Allrights reserved.
Allfeatures andspecifications subject
tochange withoutnotice.
Allscreens in thismanual aresimulated.
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Weakbottom echo, digitalreadingserratic, ornofishsignals(cont.):
2. Electricalnoisefromtheboat's
motorcaninterferewiththesonar. Thiscauses
thesonartoautomatically increase itsDiscrimination ornoise rejection
feature.
Thiscancausetheunittoeliminateweakersignais
suchasfishorevenstructure
fromthe
dispiay.
3. Thewater
maybedeeper
thanthesonar'sability
tofindthebottom. ifthe
sonarcan'tfindthebottom
signalwhileit'sinthe
automatic
mode, thedigital
will
flashcontinuously. itmaychange
therange tolimits
fargreaterthanthewater
you arein. Ifthishappens, place
theunitinthemanual
mode, then
change
the
rangetoarealistic one,(forexample,0-100 feet)
andincrease thesensitivity. As
you moveinto shallower water, abottom
signal
should
appear.
4. Checkthe
batteryvoltage, lithe
voltagedrops,
theunit's
transmitter
power
alsodrops, reducing itsability tofind
thebottomor
targets.
Bottomecho
disappearsathighspeedsorerratic
digitalreading
orweak
bottom
echowhileboat ismoving
1. Thetransducer
maybeinturbulentwater, Itmust bemounted inasmooth
flowofwater
inorderforthesonartoworkatallboat
speeds.Airbubblesinthe
waterdisrupt the sonar
signals,interfering
withitsability
tofindthebottom or
other
targets. Thetechnicaltermforthisis'Cavitation',
2.Electricalnoisefromtheboat'smotorcaninterferewith
thesonar. Thiscauses
thesonartoautomatically increase itsDiscrimination ornoise rejectionfeature.
Thiscancausetheunitto
eliminate weakersignals suchasfishorevenstructure
fromthedisplay.Tryusingresistorsparkplugs
or
routing
thesonarunit's
power
andtransducercables
away
fromotherelectrical
wiringon theboat.
NofisharcheswhentheFish IDfeature isoff:
1. Makecertain transducerispointingstraight
down. Thisisthemost
common
problem
ifapartialarchisdisplayed. SeetheFishArchsectioninyour
owner's
manualformoreinformation.
2. Thesensitivitymaynotbe
highenough.In
orderforthe unittodisplay afish
arch,ithastobeabletoreceive thefish'sechofromthetimeitenters thecone
untilitleaves.Ifthesensitivity
isnothighenough, theunitdisplays
thefish
only
whenitisinthecenterofthecone.
3. UsetheZoom feature.itismucheasiertodisplay
fisharches whenzoomed
inonasmallrange
ofwaterthana
largeone. For
example, youwillhave much
betterluck
seeing
fisharches with a30
to60foot
range
thana0to60foot
range.
This
enlarges
thetargets, allowing
thedisplay toshowmuchmoredetail.
25
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IMPORTANT
SERVICE INFORMATION!
Ifyour unit isnotworking, orifyou needtechnical help,please
usethefollowing
troubleshooting sectionbefore contacting
aservicecenterorthefactorycus-
tomerservice
department. Itmaysave
youthetroubleofreturningyourunit. See
theHowTo ObtainServicesectiononpage27if you needservice.
SONARTROUBLESHOOTING
Unitwon'tturnon:
1. Checkthe powercable'sconnection attheunit. Alsocheck
thewiring.
2. Makecertainthepowercableiswiredproperly. Theredwireconnects
tothe
positivebattery
terminal, blacktonegative or ground.
3. Checkthefuse.
4.Measurethebatteryvoltage attheunit's
powerconnector. Itshouldbeatleast
11 volts.Ifitisn't, thewiring totheunitisdefective, the
batteiyterminals
orwiring
ontheterminalsare
corroded,
orthe
battery
needs charging.
Unitfreezes,locksup, oroperates erratically:
1. Electrical noisefromtheboat's
motor,trolling
motor,
oranaccessory
may
be
interferingwiththesonarunit.Re-routingthe powerand
transducercables
away
fromotherelectrical wiring
onthe boat
mayhelp. Routethesonar
upit'spower
cable
directly
tothebattery instead ofthrough
afuse blockorignition
switch
2. Inspect thetransducercableforbreaks, cuts,orpinched
wires.
3. Checkboth thetransducer
andpower connectors. Makecertainbothare
securelyplugged intothe unit.
Weakbottom
echo, digItalreadingserratic, ornofishsignals:
1. Makecertaintransduceris pointing straight
down. Cleanthe face ofthe
transducer. Oil,dirt, andfuelcancauseafilmtoformonthetransducer,reducing
its effectiveness. Ifthetransduceris mounted insidethe hull, besure it is
shootingthroughonly
one
layeroffiberglass
andthatitissecurely bondedtothe
hull. Do NOTuseRTVsiliconerubberadhesive orMarinetexN.
24
INTRODUCTION
Thank
youforpurchasing anEagle
sonar. YourMagna
orMagna Plus
isa
highquality sonar
designed forbothprofessional andnovice
fishermen.Theseunitshaveanautomatic featurethatfindsand
displays thebottom, fish, structure, and morel Allyouhavetodois
press
theonkey. However, ifyouwishtofinetunethe unit,allyou
havetodoispress themenu key. TheMagna
series
haspowerful
featuresavailablethrougheasy-to-use menus.
Toget startedwith yourEagleunit, firstreadtheinstallation section.
Thisiswhereitallbegins. Improper
installation cancause
problems
downtheroad. Afteryou'veread theinstructions, installthe
unit,then
readtherestofthemanual. Themore youknowabout your unit,the
betteritwillperform
foryou. Takethismanual forreference when
you
headforthe
water.
INSTALLATION
MounttheMagna
inanyconvenient location,provided
thereisclear-
ance whenit'stiltedforthebestviewingangle. Rolesin thebracket's
base allowwoodscrew orthrough
boltmounting. Itmaybenecessary
toplace apiece ofplywood onthebackside ofthinpanels
toreinforce
the
panel. Makecertainthereisenough roombehind theunittoattach
the
powerandtransducercables.
Drillaholein thedashforthe
power
andtransducer cables. Thebest
location forthisholeisimmediately underthe
gimbal
bracket. This
way,thebracket coversthehole. Thesmallest holeboth thepower
and transducer cables can pass
through
isoneinch. However, you
can'tpass
apower ortransducerconnector
andanothercable
through
1
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aoneinch hole. Therefore, afterdrillingthehole, passthetransducer SURVEYINGALAKE
connector
upthrough theholefromunderthedash. Thendropthe
power
cabledownfromthefrontsideofthedash. Slide thebracket
overthehole, thenroutethetransducerandpowercablesouttheslots
in thebracket. Finally, fasten thebracket tothedash.
POWER CONNECTIONS
TheMagna worksfroma12voltDC systemonly. Forthebestresults,
runthe
power
cabledirectly tothe
boat'sbattery. Keep thepower
cable
away
fromotherboat
wiring, especiallytheengine's wires. This
willgive thebestisolation fromelectrical noise. Ifthesupplied cableis
notlongenough toreachthebattery, splice
#18gauge
insulatedwire
to it. Youcanattach thepower
cabletoanaccessory orpower buss,
however, youmayhave problems withelectrical interference. See
page 26formoreinformation onelectrical noise.
Themostsuccessful anglers onanybodyofwaterarethosewho fish
itday after
dayand yearafteryear. Eventually, they learnthehot
spots
thatproduce fish consistently. They discover
through experi-
ence
where, andatwhatdepth,theycanexpect tofindthefish they
wantatanyseason. And theyrealizethattheseproductive areas
change throughout
theyeardepending onwaterlevel, temperature,
food,andotherfactors.
WiththeMagna, anyone can eliminate guesswork and
concentrateon
theareas wherefishare likely
tobe. Even ifit'sthefirsttimeon
the
lake!
Themostefficient
way
tobecome
acquainted withabodyofwateris
tosurvey itwithyourMagna. Startwith amapofthe
lake,ifpossible,
andindicatethe
promising spots
in relation tolandmarks onshore.
Asyougoabout yoursurvey,yourMagna willtellyouthe
depth and
typeofbottom. Itwillalsoreveal suspended fish.
Keep afewmarker buoys in theboat, ready totossoverboard. When
theMagna indicates aschooloffish, throwthebuoyout. Withthe
schoolthus marked, youcanmakeyour
turnand comebacktofish in
exactly therightspot. Thisisessential when you're
farfrom shoreon
abiglake. Unless youmarktheschool offishwhen
you're
overit,
youmaynotbeabletofinditagain.
BAITFISH
Theimportance ofbaitfishtosuccessful fishing can'tbeover-empha-
sized. Theyare theprinciple foodofallgame
fish in mostwaters.
Baitfisharetheplankton feeding forage fish, suchas minnowsand
shad. Baitfishcanalso bethe
youngofgame fish, suchascrappies,
bluegill,andbass.
Most
baitfishconcentrate withinfivefeetofthesurface wheresunlight
promotes the growth ofthe
plankton onwhichtheyfeed. Onemethod
offishingistousetheMagna
tofindthebaitfishfirst. WiththeFish
IDfeature
off, aschool ofbaitfishwill look likea"cloud"onthe
display. Usually, gamefishwillbe
nearby, often directly
beneaththe
school ofbait fish.
23
MACNA
BLACK 3 amp
FUSE
l2voLr
BATTERY
MACNA
PLUS 3amp
FusE
2
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The
temperature ofwaterinthelake isseldom constantfromtopto
bottom. Layersofdifferent
temperatures form, andthe junctionofa
warm and coollayer ofwateriscalled athermocline. Thedepthand
thickness ofthethermoclinecanvarywith theseason
ortimeofday.
Indeep lakes theremay betwoormore atdifferent
depths.
Thermoclinesareimportant tofishermen because theyareareas
wherefishareactive. Many timesbaitfish willbeabovethe
thermocline whilelargergamefish willsuspend in orjustbelow it.
TheMagna candetectthisinvisible layer inthe
water, butthesensitiv-
itywillprobably
havetobeturneduptoseeit.
Theseunitshavereverse
polarity protection. Nodamage
willoccurif
thepower wires are reversed. However,theunitwillnotworkuntil the
wiresareattached correctly.
SPEEDITEMPERATURE SENSOR INSTALLATION
-MagnaPlus
Only
Mountthespeed/temp sensor ontheboat'stransominalocation
wheretheflowofwateristhesmoothest. Thereshouldbeaminimum
ofturbulence
andairbubbles inthechosenlocation.Theport(left)
sideofthetransomis
preferred, however, thestarboard (right) side
canbeusedifnecessary. Donotmountthe
speedsensorbehind
strakes, ribs,orthru-hull fittings. These
willdisturb theflowofwaterto
thespeed sensor. Inatypicalinstallation,thespeed sensor
is
mounted sixtotwelveinchesfromthecenterline ofthehull. The
sensormustalways beinthewatertofunction properly. Makecertain
thechosen location isinthewatereven
athighspeed orwhenthe
boatison
plane.
Once
youdetermine the properlocation,place
thesensor
onthe
transom. Makecertain thesensor'sbottomis
flushwiththebottomof
thehull. Markthetransominfourplaces, twoin eachslot. Drilla5/
32"mounting holeateachlocation. Mountthesensortothehull with
four#10stainless steelscrews. Useagood gradeofcaulking com-
pound
toseal thescrews. Adjust thesensorsoitisflushwiththe
bottomofthehull and
tighten
thescrews.
Ifthebase ofthetransomhasaradius, fillthegapbetween the
transomand thesensor withcaulking compound. Thiswillhelpinsure
asmooth waterflow.
Routethesensor cabletothein-lineconnectorontheMagna
Plus'
powercable. Thespeed/temp sensor isnowready
foruse.
SURFACE LAYER
ABSORBS HEAT
FROMTHESUN
EPILIMNION 760
e at
750
THERMOCLINE
MOST pRoDucTivE
ZONEFOR FISHING
680
660
500
470
22 3
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KEYBOARDBASICS Verysmall fishprobably willnotarchatall. Medium sized fish will
Theunit sounds atonewhen
youpressanykey. Thistells youthe
unithasaccepted acommand.
ON/CLEAR
Usethiskey toturntheuniton. Italsoclearsmenuselections andthe
menus fromthescreen.
OFF
Thiskeyturnstheunitoff.
MENU
TheMagna andMagna Plus havemany menusoffeaturesthatare
accessedwiththis
key.
UPand DOWNARROWS
Usethesekeys toadjustvirtuallyevery featureandfunction onthe
unit. Usethesekeys toadjust thesensitivity, chart speed, range, and
more.
NOTE:Theup arrow
keyalso stops
andstarts
thechartwhenno
menusare displayed. Inother
words,anytimeyouwishtostop
the
chart, firstmakecertain nomenu isonthescreen. Thenpress
theup
arrow
key. Thechartwillfreezeand theword"STOP"appearsatthe
toprightportion
ofthescreen. Tostartthechart, press
the
uparrow
keyagain.
showa
partialarch, ora
shape
similartoanarchifthey're in deep
water. Large fishwillarch, butturnthe
sensitivity upin deeper water
toseethearch. Because ofwaterconditions, suchas heavy surface
clutter, thermoclines, etc., thesensitivity sometimes cannot bein-
creased
enough toget
fisharches.
Oneofthebestwaystoget fisharchesistoexpand or "zoom"a
segment
ofthewater. For
example, from45to60feet. Thesmaller
thesegment, thebetterthescreen resolution willbe. Theeasiest way
todo
thisontheMagna iswiththeZoomfeature. Thisfeature
expands theechoes, making iteasiertoseedetail. Forthebest
results, turnthesensitivity upas highaspossible without
getting too
muchnoiseonthescreen. Inmediumtodeepwater, thismethod
shouldworktodisplay fisharches.
If
youseefishsignals
whentheunitisinthemanual mode, butdon't
getfishsymbols whenthe Fish 1.0.featureison,tryincreasingthe
sensitivity.
WATERTEMPERATURE ANDTHERMOCLINES
Water
temperature hasan important-if notcontrolling-influenceupon
theactivities ofallfish. Fish arecoldblooded and theirbodies are
alwaysthetemperature ofthesurrounding water. Duringthewinter,
colder
waterslows downtheirmetabolism. Atthistime, theyneed
aboutafourthas much food as theyconsume inthesummer.
Mostfishdon'tspawn unless thewatertemperature iswithin rather
narrowlimits. Thesurface temperature meterbuilt intotheMagna
Plus helpsidentify thedesired surface waterspawningtemperatures
forvarious
species. Troutcan'tsurviveinstreamsthatget
toowarm.
Bass andotherfish eventually
dieoutwhenstockedin lakesthat
remaintoocold during
thesummer. Whilesomefishhave awider
temperature tolerance than others,each hasacertain rangewithin
whichittriestostay. Schooling fishsuspended over
deep waterlieat
thelevelthatprovides thistemperature. Weassume they arethe
most
comfortablehere.
L LI
4 21
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FISH ARCHES DISPLAY
-General
Fisharches are created whentheconeofsound passes
overafish.
Thedistancetoafishwhentheconefirststrikes it isshown as"A"
below. When thecenterofthecone strikes thefish, thedistanceis
shorteras shown "B". Astheconeleaves thefish, thedistance
increases again asshown in"C".
WhentheFishl.D. mode isoff,thedepth ofthewaterwillaffectthe
sizeandshape ofthefisharch duetotheconeangle diameter. For
example, iftheconepasses
overafish in shallow
water,thesignal
displayed onthe Magna maynotarch atall. Thisisduetothenarrow
cone diameterandtheresolution limitationsofthedisplay.
Thelights flashforabout tensecondswhenthe Magna
isturnedon.
Threemenusappear, oneaftertheother. Themenus are thelights
(LAMP), feet-meter selection (FEET/METER), andcontrastadjustment
(DARK/LIGHT). Toturnthe
lights
on,presstheuparrow key. To
switchfromfeettometers, press thedownarrow keywhenthe proper
menu appears. Toadjustthecontrast, waitfortheDARK/LIGHT
menu toappear. Nowpress theuparrow keytodarken
thescreen,
thedownarrow tolighten it. Themenusdisappear
afterafewsec-
onds. If
youdon't
wanttowait,press theON/CLEAR keytoclearthe
menusfromthescreen.
WhentheMagna isfirstturnedon, the
displayappears similar tothe
onebelow. Theunitisintheautomatic mode and theFishIDfeature
ison. Thedepth range displays ontheleftsideofthescreen. Inthis
example, therange isfrom0to60feet. Thedigital
bottom
depth
displayshows atthe topleftportion
ofthescreen.
MENUS
TheMagna andMagna Plus
usemenustoguideyouthrough theunit's
functions andfeatures. The
menu keyaccesses thesefeatures,
allowingyoutocustomize theunittoyourparticular
needs and
water
conditions. Allyouhavetodotoleaveonemenu andenteranother is
press themenu keyrepeatedly. If
youevergetlost in
themenus,
simplypress
theON/CLEAR key. Thisclearsthemenusfromthe
screen.
BOATS DIRECTION OFTRAVEL
LI—-
373FT
4-C
.1 1
A
a.
B C
.'n'..l
20 5
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Menuschangedepending on
themodetheunitis in. Forexample, if
theautomatic mode isturnedoff,the
sensitivity menuchanges from
"AUTO
SENS"to"MANSENS." Other
messages mayappear
in
menuboxesornew menus canappear, again depending onprevious
selections.
OPERATION
AUTOMATIC
WhentheMagna
isfirstturned
on,the
automatic featureisenabled. Thisfeature
automatically adjusts theunit's rangeand
sensitivity according towaterconditions. It
always keeps
thebottom depth displayed
in thelower
portion
ofthescreen.
Toturntheautomaticfeature off,press the
menukeyuntiltheAUTO/MAN menu
appears. Nowpress
thedown
arrowkey.
Thishighlights theletters "MAN." Theunit
isnowin themanual mode. Waitafew
secondsand themenu willscroll offthe
screen'sleftside. Pressing theON/CLEAR keyalsoclearsit. Toturn
theautomatic featureonagain, repeat theabove steps, exceptthis
timepress the
up
arrow
key.
RANGE
Youcan'tadjusttherange
whenthe
Magna isintheautomatic mode. Itis
adjustable whentheunitisinthemanual
mode, however. Todoso,firstput
theunit
inthemanual mode. Now
press
theON/
CLEAR
keytoclearthescreen. Then
press
themenu key until the
"RANGE
SEL"menu appears asshown.The
current rangeshowsatthebottomofthe
menu. Inthis
case,
therangeis60feet.
Now
pressthe up
arrow
keytodecrease
therange, thedownarrow keyincreases
therange. Afteryouselectthedesired
Both8degreeand 20degree transducers giveaccurate bottom read-
ings,eventhough thebottom signal ismuchwideronthe20degree
model. Thisisbecause youareseeing moreofthebottom. Remem-
ber,theshallow
edge ofthesignal showsyou the
truedepth. The
restofthesignal tellsyouwhether
youareoverrocks, mud, etc.
SIGNALINTERPRETATION
YourMagna givesanaccurate
picture ofthebottomthat your
boatis
passing. Abottom offirm sand,gravel, shell,orhardclayreturnsa
fairlywide signal. Iftheautomatic mode isoffandthesignalnarrows
down, thenitmeansthat youhavemoved overamudbottom. Mud
absorbs thesound
waveand returns aweaksignal. Turn upthe
sensitivity toseeabetterbottom signal.
Big rocksorstumps onasmooth bottomsend backsignals abovethe
bottomlevelsignal. Theheight ofthe
signaldepends onthe target's
height. Asyoupassoverapost, itshould beclearly visibleas ashort
line extending above thebottom
signal.
Asteep slopereturns awidesignal, the
steeper
thewider. Signals
returned fromahighunderwater cliffare usuallythewidestofall.
AUTO
6 19
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