Eagle Six-Sixty User manual

LImO IN U.S.A. 966-0087-01
41
EAGLE
MODEL SILENT
SIX/SIXTY
INSTALLATION INSTRUCTIONS
EAGLE ELECTRONICS
EQ. BOX 669,CATOOSA,OKLA.74015
- - IA DiviiOhOl
Lcwrance Electronics Inc
HOWTO OBTAINSERVICE
EagleElectronicswillprovidequek andefficientservice
with genuine
Eagleparts
should
youeverrequireit.If youdorequire service, callor
writeusatthe addressbelowbefore sending intheunit.We
maybeable
tosave
you
theinconvenience of
sending
theunitbackfor
repairs.
If
you
dohavetoreturntheunitforservice,
please
enclose aletterstating the
problemthat you are having withthe unit. This will assistus in the
testingandrepair
of
yourdepth sounder.
Mailto: EAGLE ELECTRONICS
P0.BOX 669
CATOOSA, OKLAHOMA 74015
If
youliveoutofthestateofOklahoma,call1-800-331-2301.
If
youliveinthe stateofOklahoma,callcollect918-266-5373.
SCHEMATICDIAGRAM & PARTSLIST
Shouldyou desire aschematicandparts list foryourEAGLEdepth
sounder,send$1.00 tothe addressabove anditwill bemailed toyou
promptlyPleasebesureand give
usthemodelandserial
numberof
your
EAGLE.
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INTRODUCTION
Thank
youforselectingawater-
proofEAGLE depth sounder. We
believethatitisthefinest unit
available today, manufactured
right here intheU.S.A. topreci-
siontolerances.
lbfully enjoythe advantages
thisequipment brings toyou,we
suggestthatyoureadthisman-
ualthoroughlybeforeanyat-
tempt
atinstallation oruse of
thisproduct.
Please filloutthewarranty card
andmailittoEAGLE ELEC-
TRONICS. This will register
your1yearFULLwarranty.
Wesuggest thatyoukeep the
original cartonthat the EAGLE
was shippedin, so thatifitever
needs tobereturnedtothefac-
toryforrepairs,
asuitable con-
tainer will beavailable.
POWERCONNECTIONS
Powerforthe depth sounderis
suppliedbytheboat's12-volt DC
electricalsystem. Power maybe
pickedup atanaccessory or
powerbuss, but if youhaveprob-
lems withelectricalinterference,
whichisindicatedbyextraneous
flashesonthedial,itcan be
minimized
byconnectingpower
directly to thebattery(See
Figure 1.)
Ifalonger powercable isre-
quired, useordinary #18lamp
cableavailableatanyhardware
orelectrical supply store. Splices
shouldbesoldered.Ifthiscan't
bedone, usecrimp-typesplices.
Simpletwistingofsplicesmay
resultinintermittent
power
connectionswhichcan cause in-
terference.'Ihpeall splices with
electrical tape.
FISHSIGNALS
Here aresome thingsthatwill
help youunderstand thesignals
thataredisplayedonyour
Eagle:Abigfishreturnsawide
signal while asmallfishreturns
anarrow one.Aschool ofbait
fishorminnows,
nearlyalways
near thesurface, returnsa great
many thin, rapid signals. Wide
signalsbeneath
indicatethe
gamefishwhich are oftenpres-
entunder the school oflittlefel-
lowstofeed on them.
If
youarecruising atthreemiles
per hourwhile huntingfishwith
yourEagle, asingle fish30 feet
deepwill returnasignal for ap-
proximatelyonesecond. (Three
milesperhouris4.4 feetper
second andthediameter ofthe
circlecovered bythetransducer
is approximately fourfeetat
that depth.) The signal returned
byafish15 feetdeep wouldlast
halfasecond, andfrom afish60
feetdeep thesignal wouldlast
approximately
twoseconds.
Thisis agoodpoint toremember
because fishoftenschoolina
horizontalplane, sometimes
ratherwidelyscattered inthat
exactlevel, butnot allvertically,
andasignal thatlastslonger
hastobemadebymorethanone
fish.Ofcourse,fishsuspendedat
differentlevels,even if
onlya
few inches higher or lowerinthe
water, willreturndifferent sig-
nalsatthe
correspondingdepths
onthedial.
Remember, manykindsofgame
fishlikesharp drop-offs,rocky
ledges,
andunderwater cliffs.
But, asyourboat movesacross
these spots,theEagle will be
unableto showthe fishbecause
thesloping bottomsends back
suchawidesignal.
Manykindsoffishremainsus-
pendedbetweenthewatersur-
faceandbottomduring hot
weather.Crappies will usually
lieatauniform
depthsimilarto
ahorizontalblanketinthe
water.
A
bigschool may extend 100 feet
ineachdirectionandas youpass
overityouwillgetan almost
constantsignal,plusotherflash-
ingafew inches above andbe-
low. Aschool ofwhitebass isn't
likelytocover suchabigarea as
aschool of
crappiesometimes
does, especially inthe summer
andfall. The signals will show
these fishoccupying agreater
spreadvertically (8to 10feet).
The largergamefishsuchas
bass andwalleye aren't likely to
be so tightlygrouped aswhite
bass, crappie,
or other panfish,
andthe individualmembers,
beinglarger,return stronger
signals.
1 18
SPECIFICATIONS
Dimensionswith knobs andgimbals .711 x8Wx 61)
Dial 0-60 (outer),0-360 (inner)
Voltage 12 volts D.C. (operates10-15
volts)
Current
Drain 250ma., oneecho
PulseWidth 200-1000 cs,adjustable
OutputPower 200 wattspeaktopeak
(typical)
25waftsRMS
4AMP FUSE
Fig. 1
To
12 Volts DC
(Positive)
Ground
(Negative)
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TREES INTHE WATER IMPORTANT The bracket sides will have tobe
The signals onthe
dialshownhere indi-
cateanunderwater
treewitha few fish
aboveit.The wateris
50feetdeep,thetree
20feettall,andthe
fisharebetweenten
and13 feet deep.
Limbsatvarious
depths returnindi-
vidual signals andac-
count forthewide
band ofsignals onthe
dial. Brushappears
similar,though notso
tall.
Bass andpanfish
often hang around
submergedvegetation,
not onlynearthe sur-
facebut down to
depths of25or30feet,
dependingonthe
thermocline.To detect
them,anchorbow and
stern so yourboat
can'tmove. Constant
signals indicatetree
limbs. Signalsthat
come andgo orshift
upanddownarefish
—limbsdon'tmove.
Wheninstalling the powercable,
make certainthatthein-line
fusesuppliedwiththeunitisat-
tached tothered conductorof
thepowercableasclosetothe
powersourceaspossible.
This
will protect both theunitand
thepowercable incaseeitheris
ever shorted. Aconnectoris
• supplied
to attachthe fuse tothe
- power cable.
The positiveconductor
inthe
power cable isthered conductor.
• The unitis protected fromacci-
• dental polarity reversals andno
damagewill resultif
battery
connectionsarewrong. However,
theunitwill notwork.
MOUNTING
The depthsoundercanbein-
stalled inanyconvenientloca-
tion whichhas aflatsurface.
The adjustableyoke permits
mounting oneither abottomor
overheadsupporting surface.If
theunitistobelocated inthe
vicinity ofacompass, runitin
positiontemporarilytomake
sureitdoesnot affectcompass
readings. If compass heading
• changes, choose analternatelo-
cation.Note:the unitmust be
running
when
youmakethis
test. Holesinthebase ofthe
bracket allowwood screworbolt
mounting.
Threadboth knobs partially into
themountingbushings onthe
case.The gimbalbrackethas
slotsinthetopofitthatallows
• the unitto"snap" inwithout
removingthegimbal knobs.
Theseslotswill clear thethreads
ofthe gimbalknobs, but net the
Fig.21 mounting bushing onthe case.
spread slighltyto clear thegim-
bal bushings, but will returnto
theiroriginal positionwhenre-
leased.Holesinthe gimbal
bracket alignwiththegimbal
bushings onthe caseandwill
notallowtheunittocome ofT
even insevere wave conditions.
lbremovetheunit, simply
loosenthegimbal knobs,spread
the bracket sides awayfromthe
case, andpull theunitupand
outofthebracket.
TRANSDUCER
INSTALLATION
Two differentmountingmethods
areavailable toinstallyour
EAGLE transducer, either
transom mountorshoot-thru-
hull. Althoughthetransom
mount will work onmosthulls,
werecommendthattheshoot-
thru-hullmethod be used only
onsolid fiberglass hulls. The
transducer signals willpenetrate
singlethicknesses offiberglass,
but will notgothroughporous
materialssuchaswood or foam.
Thesignals alsowill not pass
through
airpockets orvoidsin
the fiberglass laminations. Re-
gardlessofwhich mounting
methodisused,the installation
shouldbemadeinan areathat
hasminimum waterturbulence,
airbubbles,andwhere the water
isthesmoothest.
Thetransducercable shouldbe
routed away fromotherelectri-
calwiring. Donot cut thetrans-
ducer cableif
itistoolong.In-
stead, coil itand store the excess
inan unobtrusive area.'frans-
ducer extensioncablesModel
TEC-10 are available thatwill
extendthecable 10 feet. Ifthe
17 2
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transducercableneedstobeex-
tended longer than 10feet,the
depthsounderandtransducer
will need tobereturned tothe
factoryforre-alignment.
1vo othertransducers areavail-
ableforyourEAGLE depth
sounder.ModelXD-2 is ahigh
speedplastic unitthatcan be
transommountedorcan shoot-
thru-hull.Itworkswellondeep
vee hulls andaluminum boats.
The othertransducer
(Model
XD-3)
isfortrolling motor
mounting orshoot-thru-hull.
Fig. 3
XD-3 Ji
Aspecialbracket isavailablefor
theXD-2
transducer that will
putitbelow
thesevere cavita-
tionlayerthatissometimes
present
onaluminum boats.The
modelnumberforthisbracket is
XMB-2.
1. Mounting inside the hullis
recommendedforfiberglass
hullsin anarea thatdoes not
have airbubblesintheresin
orseparatedfiberglasslayers.
Thesonar
signal mustpass
through
solid fiberglass. A
successfultransducer installa-
tioncanbemade on hulls
thathaveflotationmaterials
(suchaswood orfoam)inbe-
tween layers offiberglassif
thematerialisremovedfrom
the chosenarea.For example,
somemanufacturers use a
layeroffiberglass,then acore
ofbalsawood, andthen the
outerlayeroffiberglass.By
removingtheinnerlayerof
fiberglass andthebalsa wood
core,theouterlayerof
The signals returned
fromarocky
bottom
arequiteconfusing
whenyoufirstsee
them. The EAGLE's
dialwill indicate the
levelofthebottomat
thecorrectdepth, but
itwill alsoshowclear
thinsignals above and
belowthewidermain
bottomsignal. This is
explained bythe fact
thattherocksnear the
outeredge ofthe cone
ofsoundwavesare
fartherfrom the
transducerthan those
inthe center,while
thetopsofthelatter
are closerthan the
bottom.
This drawing also
showsthe typical sig-
nalsindicating a
school of
white bass or
bluegills at adepth of
twenty feet.The sig-
nalsarebrighter than
those returned
bybait
fish.
3 16
Fig. 2
SIGNALSRETURNEDBY AROCKY BOTTOM
XD-2
SHOOTING THROUGH THE
HULL
Fig. 20
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Smallminnowsor
bait fishappearonthe
dial as thin,pale lines.
If
theyare tightly
schooled theymay
coveradepth offrom
five totenfeetonthe
dialwitha few pale
lines forindividual.
minnowsatthebottom
oftheschool. Your
EAGLE
will indicate
even asingle minnow
30 feetbeneath the
surface ofthewater.
Obviously, theback
ofabigfishoffers a
largersurfacetore-
flectthe signal than
theback ofasmall
fish. Consequently, yop
getawiderand
brightersignal on the
dialand, eventhough
youcan'ttelltheexact
size ofthe fishfrom
the signal, itdoes give
youagoodclueso that
youcaninstantly
tell
bigonesfrom little
ones.
fiberglassandgel coat are
exposed. The transducer can
then be epoxied directly to
thisouter layer.(See Figure
5.) When epoxy
ispouredinto
thehole andthetransducer
placed
intothe epoxy, thehull
is still structurally rigidand
noweak points aremade.
2. The chosenareashouldbein
theaft one-thirdofthehull
onplaning
boats, andforward
ofthe engines and/orwater
intakes indisplacement
hulls.
Watershouldflowsmoothly
inthisareaanditshouldstay
inthe wateratallspeeds.
3. Before permanently bonding
the transducer tothehull,
trialruns arerecommended
tofindthebestmounting lo-
cation.Onceanareahasbeen
determinedtobe agood spot
forthetransducer to be
mounted,addsome waterto
thearea,andplacethetrans-
ducer in itface down. This
willeliminate air betweenthe
faceofthetransducerandthe
hull.Plugthe
transducer
into
theunitandturnthedepth
sounderon. Operatetheboat
atall speedsand move the
transducer untilthebestloca-
tionisfound for maximum
signalreception and
minimum cavitation noise
(cavitationiscausedbywater
turbulence andshowsupas
narrow signals allaround the
sonardial.)
4. Ifthe chosenareaisvoidof
potential problems,
sandthe
surface ofthe hullandthe
faceofthetransducer with
100 gritsandpaper. The sur-
facemustbeflatenoughso
thattheentiretransducer
faceis in contactwith the
hullprior tobonding.
5. Build a smalldamoutof
caulking compound ormodel-
ingclay around the chosen
areaofthetransducer.(Do
notusePLAY-DOll) (See
Figure7.)
15 4
WIDTH OF SIGNAL INDICATES SIZEOFFISH
4
Fig.19
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6. Use agoodquality two-part
epoxy
tobondthetransducer
tothehull. Donotuse
siliconerubber sealerorany
adhesivethatdoesnotget
rockhard. Followtheinstruc-
tions ontheepoxypackage
andmix itthoroughly..Apply
asmallamount ontheentire
faceofthe transducerand
pour 1/16"thicklevelintothe
areacontainedby theclay
dam. Placethetransducer
into the epoxy
bypushingand
turningto force alloftheair
bubblesoutfromunder the
transducerface.The trans-
ducer faceshouldbe parallel
withtheboathull, witha
minimum amountofepoxy
betweenhull andtransducer.
Weightthetransducer down
untiltheepoxy cures.
7. Route thetransducer cable
alonggunwalesand away
frompowercables.
TRANSOM MOUNT
1. Loosely attachthebracketsto
the transducer with the
hardware provided.
2. Locatethe bracketwhere the
flowofwater is smoothest
withminimum turbulence
andbubbles.
Also, thebracket
ortransducer shouldnotin-
terferewiththeboattrailer
orhaulingoftheboat.
3. 1'ypically,thetransducer
shouldbelocatedhalf-way be-
tweenthecenter ofthe
transomandtheoutsideedge
ofthehull. (See Figure 8.)
The transducershouldbe
mountedaway fromstakes,
ribs,or otherhullfittings
thatcan causeturbulence.
4. If
thehulldeadriseexceeds 4
degrees,ashoot-thru-hull
mount onthecenterline of-
thehull oranoptiQnaltrans-
ducer shouldbeused. (See
Figure9.)
5. Placethebracket against the
transomintheselectedarea
withthebottomofthetrans-
ducer flushwith thebottomof
thehull. Alignthetransducer
withthebottomoftheboat
hullbyusing astraightedge.
Mark
thetransomfor drilling
Your EAGLEtrans-
latestimeintodis-
tance — thefarther
the soundwavesgo,
the longer ittakes
themtoreturntothe
transducerandthe
greaterthedepth
shownonthedial.
Nowhereisthisshown
more clearly than
whenyourboat passes
overasteep, rocky
underwater ledgeor
cliff; eithervertical or
inclined ata steepangle.
Assumethetopof
thecliffis15 feetbe-
neaththesurface of
thewater, andthebot-
tom is 50feetdeep.
Soundwaveswill hit
roughspots onthe cliff
allthewaydown. As
theresult, the signals
onthedialwill cover
anarea
extending
from15 to50feet — a
conditionthatcould
easily
leadtoconfu-
sion untilyouunder-
standit.
5 14
Fig.7 SIGNALS
FROMSTEEP, ROCKYLEDGES
Fig. 9
Fig. 18
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MUDBOTTOM CAUSES THE SIGNAL TO FADE
Whenyouare hunt-
ingfish, with thegain
adjustedproperlyto
returnaclear, bright
signal from abottom
ofgravel,sand,or
shell,youwill some-
times see thesignal
disappear.
This doesn't
meanthatyouhave
suddenlycome toex-
tremely deepwater—
the dialwouldhave
shownthe drop-off
with a wideband of
signals inthiscase.
Instead, your
boatis
nowaboveamud bot-
tom.Mud absorbsthe
soundwaves.Thrnup
thegain. Thebottom
signal maybefaint
fromabottomofde-
cayingvegetation
under deep water. Fish
will still show onthe
dial, however. Back
overahardbottom,
you'llgetmultiple
signals. Fig. 17
themountingholesatthetop
ofthe slotsinthe bracket.
6. Mountthe assembly
tothe
transomwith two#10 screws.
Alignthefaceofthetrans-
ducerwiththebottomofthe
hullwithastraightedge.
Tightenallscrews.
7. Routethetransducer cableto
thedepthsounderunit. Do
notcutthetransducer cable.
Ifitistoolong,coil and store
theexcessin anout-of-the-
way location.
S. Make atestruntodetermine
the results. Someboathulls
require lowering
the back
edgeofthetransducer 2° to
6°. Iftherunwas satisfactory,
drilltwomoreholes inthe
• bottomoftheslotsandinstall
two more #10 screws.Note:
The transducer mustbe
• against thetransom forgood
results. After lockingin place,
fillanyvoidsbetweenthe
transom andthetransducer
with caulking compound,
epoxy, or silicone adhesive.
OPERATION
SENSITIVITY AND
"ON-OFF"KNOB
Thisknoboperatesinamanner
similar tothe volumecontrol on
aradio. Thrningtheknob
clockwise will turnthe uniton,
andturningtheknobback the
full counterclockwise
position
will turntheunitoff. Thrning
theknobinacontinued
clockwise manner will increase
thereceiver sensitivity and
weaker echosfromdeeperwater
can andwill be observedon the
dial. Aftermounting thetrans-
ducer,turntheunitonbyturn-
ingthesensitivity knob
clockwise. Youwill seethecon-
stantsurface signal atzero.Be-
fore long,youwill seeanother
signal — attenfeetifthewater
istenfeetdeep.This signalindi-
catesthebottom.It,too, should
alwaysshow.
Continueturning
theSensitivity
controltoward theright andyou
will see a second bottomsignal
atdouble the depth ofthefirst,
or20feet.The soundwaveshave
hitbottom, bounced
back, hitthe
surfaceofthewater,then
bounced
downandup again.
Overafirmbottomyoucan in-
creasethe sensitivity untilthe
dialshowsthreeorfourbottom
signals atmultiples oftrue
depth.
The sensitivity isadjustable and
youshould alwayssetittore-
turn asteady bottomsignal —
nearly asbrightasthezero sig-
nal — regardless ofdepth. 'Ilirn
theknobcounterclockwisewhen
youbegintogetthedoublebot-
tom signal; clockwise whenthe
bottomsignal beginsto fade. lb
showfishthesensitivity control
shouldbesettoshow astrong,
brightbottomsignal. Many
fishermenprefer to runthesen-
sitivity controlveryhighwith
thesecondbottomsignalshow-
13 6
Mud anddecayed vegetation
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ingto insure thattheyseeall
theunderwaterdetail aswell as
fish.
NOISE SUPPRESS
CONTROL
The noise suppress
controlknob
canbe usedtocutdown or
eliminate false flashesonthe
dial. Thesefalse flashescanbe
causedbyignition interference
fromtheboat'smotor orbyair
bubblespassingovertheface of
thetransducet
Ilirningtheknobclockwise in-
creasstheamount ofnoisesup-
press. Alwaysuseaslittlenoise
suppress aspossible, because an
increase initcutsdownon the
ability
oftheunittoshow sepa-
rate signals orobjects (suchas
fish)close together.
Increasing noisesuppressdoes
notaffectthe
sensitivityofthe
unit.
RANGE
Therangecontrolis usedto
selecteither the0-60' orthe
0-60fathom (360')scale. The
NoiseSuppresscontrolknobis
usedtochangethe scales. By
pulling the
knobout,the0-60
fathomrangeisselected,and
pushing theknobinswitchesthe
scaletothe60'range. Withthe
controlinthe60' position,
the
rangeshouldbereadon the
outside 0-60scale.Withthe
controlinthe 60fathom
position,
therange may beread
infathoms on theoutside 0-60
scale,ormay
beread infeeton
theinside 0-360'scaleonthe
faceplate.
HOW TOUSE YOUR
EAGLEDEPTH
SOUNIJER
The word'Sonar"isanabbrevi-
ationof
Sound,Navigation,and
Ranging. Itwas developed dur-
ingWorldWar IIas ameans of
tracking enemysubmarines.
Soundtravels atapproximately
4,800feet
persecond
through
wateras compared
toapproxi-
mately1,100feet persecond
through
air.
The way a sonarworksinits
simplestformisanelectrical
pulse isconvertedinto asound
wavebythetransducer and
transmittedintothewater.
Whenthiswave strikes anob-
ject, itrebounds.Since thespeed
ofsoundthrough wateris
known,thetime lapsebetween
thetransmitted
signal andthe
receivedecho canbemeasured
andthe distancetothe object
determined.
Some
fish, including
bass, catfish,walleyes,
andcrappies, occa-
sionallylie righton
thebottom.Even here
theEAGLEwill show
themas you pass over,
provided
thebottomis
smoothsand,shell, or
gravel. Figure16
showsahardbottom
withthesensitivity
controladjustedso
thatastrongbottom
signalisdisplayed
withtwo fishat20
and21feet. Asecond
echomay bedisplayed
thatistwiceasdeep
astheactualbottom
signalwhenthesen-
sitivity
controlis
turneduphighenough
to seefish.
This iscausedby
thesoundwavesre-
flecting fromthebot-
tom,bounce backfrom
thewater's
surface,re-
turntothebottomand
reflectbacktothe
sonarunit. Many
fishermenprefer to
runthesensitivity
controlveryhighwith
the secondbottomsig-
nal showing
toinsure
thattheysee allthe
underwater details as
well asfish.
The second echo is
shown at50feetin
figure 16.
7 12
HARDCLAY,SAND,GRAVEL,SHELLBOTTOMS
PRINCIPLE OF SONAR
flfl)))flfl)flflfl)))fl
.( (((( ((((( ((( ( ((( ( ((((((K
SIGNAL SENT BY LOCATOR BOUNCES BACK FROM
TARGET. TIME LAPSE INDICATES DISTANCE TO TARGET
Fig. 11
Sandbottom
Fig. 16
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The sensitivitycon-
trol onyourEAGLE
might
becompared to
thevolume on a radio.
Thrn thesensitivity
knobto the right and
youincreasethe re-
ceiversensitivity;turn
ittotheleftandyou
reduceit.This feature
isprovided so thatyou
can use your EAGLE
overbothdeep and
shallowwater andyou
shouldalways adjust
thegainso thata
brightbottomsignal
shows onthedial, re-
gardlessofdepth. Jf
youfail todoso and
have only afaintbot-
tom signal the dial
will fail toshow fish
inthewater between
thetransducer andthe
bottom. This condition
is showninthedraw-
ingabove — thefish
aretherebut they
aren't shownon the
dialbecause thegain
issettoo low.
The Eagle depth soundertrans-
mitsahigh frequency
sound
wave (which isinaudible tofish
as wellashumans)through
the
watet Atthe sametime, a high
intensity neonbulb whirls at a
constantspeed behind thedial
onadiscdrivenbyanaccurately
governed
motor.The bulb is
lighted everytime thetransmit-
terfires.This provides avisual
reference
point onthe dialwhich
isusedas astartingpoint to
measuredepth, andas anindi-
catorthatthedepth sounderis
on.Even though theneonbulb
flashes, ithappensso oftenthat
thehuman
eye seesit as a
nearlyconstant light.
The bulb alsoflashes atthe
point onthedial that indicates
the depth.The point isindicated
bythelength oftime ittakes the
soundwavestoreachthebottom
andreturn.Inaddition,echoes
returned fromanyobject
inthe
waterbetweenthesurface and
bottomfire thebulb, too. Since
these echoes are alsotimed, they
show the exactdepth ofanyfish
— orany number offish — in
thewater. Andbecausethe
soundwavesfrom thetransducer
godownintothewaterin anar-
row cone angle,theytell,within
amatter ofafewfeet,thefish's
locationaswell asthe depth.
Ata depth of10 feet, thecone
coversacircle that is approxi-
mately
onefootindiameter; at
15feetit istwo feet wide, at20
feet,threefeetwide, thecone
diameter is fourfeetwide.Re-
gardless ofdepth, the coneof
soundendsatthebottom.But
anecho is alsoreturnedfrom
anyobject
betweenthe trans-
ducer andthe bottom.
WEAKSIGNAL INDICATES GAINTOOLOW Fig. 12 ak
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EAGLE "U:
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EAGLE ELECThONOGG,,!G,!,.
Fish: 17 ft.
D,pth: 35
Fig. 15
11 8
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Asyou moveaway fromshore on
adeep lake, thebottom signal
will gradually movearound the
dialuntilitreacheszero. Ifthe
dialiscalibratedtoadepth of60
feet,thewateris60feetdeep.
Continuefurther, andthebottom
signal will start around again.
Addwhatever figure it showsto
60to get thecorrectdepth. The
inside dialontheEagle Model
Silent
Sixty 1 iscalibrated from
60to 120feettohelp youread
depths greaterthan 60feet.
Other Eagle modelshave dual
ranges thatallowyoutochange
toadeeperscale when yougo
deeperthan60feet.
SIGNAL INTERPRETATION
BecauseyourEagle isbothex-
tremely
sensitive andpowerful,
itcan give you anaccurate pic-
tureofthekindofbottom over
which yourboat is passing.A
bottomoffirmsand, gravel,
shell, orhard clayreturnsa
bright,fairly
widesignal. If
you
aretraveling
oversuchabottom
andthesignal weakens,it
means thatyouhavemovedover
asoftmud bottom.A soft bottom
absorbsthesoundwaves and re-
turns aweak signal. Inthiscase,
simplyturnupthesensitivity to
getagood bottomreading.
Alevel bottom with scattered
rocksreturnstheusualbottom
signal— plussecondary
signals
bothaboveandbelowit. This is
causedbythedifferent distances
thesound waves travel. Those
thatgo straightdown, hit arock,
andcome back indicate, cor-
rectly, that thetopoftherockis
above thelevel ofthebottom.
Butthe soundwaves thathit a
rocktoward theouter edge ofthe
cone ofsound wavesand arere-
flectedback tothe transducer
travelfurther. Consequently,
theirsignals appear belowthe
tottomsignal.
Asmoothbottomofsolid rock
returnsawide, brightsignal.
Brokenrock ofvarious sizes
sendsback anevenwider one,
with occasional flashesabove
andbelow
thelevelofthetrue
bottom, thoughthese signals
aren'tso distinct asthe ones re-
turned
byscattered rockson a
smooth
botto,m.
Bigrocksorstumps on a smooth
bottomsendback signals above
thelevel ofasmooth
bottom,the
distance depending ontheir
height. If
youwatch asyouap-
proach apostoratree, however,
youwill oftenseethe signal
climbup,thendescendtheother
side asyoucontinue.
Asteep slope returnsawide sig-
nal, thesteeperthewider,with
thesignal returned
from ahigh
underwater cliff
being the
widest.The sureproof ofa
drop-off
isthe suddenchange of
theregular depthsignal to a
wideone, then backtotheusual
width,but eithermoreshallow
ordeeperastheboat moves
past.
Brushwill returnflashesof
varyingheights above thebot-
tom signal.Weeds alsotie in
with the bottom, although they
returnweaker signals than
brushortree limbs.In most
lakes, weedsdon't grow inwater
morethan 12or15 feetdeepbe-
cause ofthe lackofsunlight.
Weeds make a greatmanythin,
pale signalson thedial.
The nicestbottoms
tosurveywith your
EAGLE are thosethat
returnaclear, bright
signal, with no spikes
eitherabove orbelow
itfromscatteredrocks.
Thisistheeasiest bot-
tom signalofallto
readandfish atany
depth above itshow up
plainly onthedial.
Nothingismore
gratifying thantofind
abigschoolof
largemouthbass over
clean gravelorwall-
eyesoverasmooth
sandbar — placesthat
these two popularfish
like andthat areeasy
to fishbythebottom-
bumping
technique.
It is easytogetmul-
tiple signalsonthe
dialfrombottomsof
thistype. If
you are
over water20 feet
deep, forexample, and
turnupthe gainyou'll
get signalsat20 and
40feet.
9 10
DETECTINGASMOOTH BOTTOM
Gravel orHard Clay
Fig. 14
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