Specifications

SimradSH90
Tip
ThemostpracticalwaytousetheAGC(AutomaticGainControl)istorstswitchit
off.Adjusttheechopresentationusingthegainuntilyouhavethebestpossibleresult,
thenactivatetheAGC.
TheAGCworksbestwithevenbackground(homogenousnoiseconditions)and
pronouncedtargets.WithuniformsonarconditionsyoumaybenetfromstrongAGC
compensation.However,ifyouarelookingatscatteredsh,reducetheAGC,andtry
toaddgaininstead.
Ifyouworkclosetoothervessels,thenoisefromtheirpropellersmaybemisinterpreted
asechoes.Thiswillalsoreducethevisibilityofotherechoes.ReducetheAGC.The
sameappliesifthebottomconditionsplaceyourvesselwithdecreasingdepthonone
sideofthevesselandyourtargetsontheotherside.
Ifyouhaveverystrongechoesfromalargeschoollocatedclosetoyourvessel(typically
closerthan150meters),werecommendthatyoureduceorswitchofftheAGC.Thisis
becausetheAGCltermisinterpretstheschoolfornoise.
KeepinmindthattheltersintheSH90areimplementedin“series”.Thegain
compensationsaremadebeforetheAGC.Forthisreason,yourgainsettingwillalways
haveaneffectontheAGC.
Relatedtopics
•WhatisAGC?onpage102
Procedure
1ClickeithertheHorizontalorVerticaltabtoopentherespectivemenu.
2ObservetheAGCbutton.
3Clickeithersideofthebuttontoleafthroughtheoptions,orthemiddleofthebutton
toopentheparameterdialog.
AdjustingtheReverberationControlledGain(RCG)
Purpose
TheReverberationControlledGain(RCG)regulatesthereceivergainindividuallyfor
eachofthereceivingbeams.
TheRCGlterwillenhancethevisibilityofschools,andreducethereverberationfrom
bottomandsurfaceechoes.
Scatteredshcanbeperceivedasreverberation.TheRCGfunctionmustthereforebe
usedwithcareifscatteredschoolsaretobedetected.
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