Simrad SU90 - Adjusting Sonar Range; Adjusting TVG (Time Variable Gain)

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381291/C
Controllingthegainandrangesettings
Topics
Adjustingthegain(echosensitivity),page56
AdjustingtheTVG(TimeVariableGain)setting,page58
Adjustingthesonarrange,page58
Adjustingtheintensityoftheechopresentations,page60
Changingthetilt,page60
Adjustingthebearing,page62
Adjustingthegain(echosensitivity)
Someechoesareweakwhileothersarestronger.Tocompensateforthisitisoften
necessarytoadjustthesensitivityoftheSU90.Thisadjustmentiscommonlyreferred
toasgain.
Context
Youcancomparethisgainsettingwiththevolumecontrolonyourcarradio.When
thegainisincreased,theechoeswillappearstronger.Weakechoeswillbeeasierto
see.However,sinceyoualsoincreasetheacousticnoiseinthereception,theSU90
presentationswillalsoshowthisnoise.Toomuchgainmaytherefore"distort"the
presentation.
Comparingthegainfunctionwiththevolumecontrolonyourcarradioisnotvery
accurate.Infact,thegainintheSU90isconstant.TheGainfunctionisusedtoadjust
thesensitivity
.Thisdonebycontrollingtheminimumlevelofdetection.Whenyou
increasethegainlevel(morepositivenumber),youreducetheminimumlevel,andthus
increasethesensitivity.
Theechostrength(A)changeswithtime.Theminimumlevelofdetection(B)isadjusted
upordownwiththeGainfunction.IncreasingtheGainwithamorepositivenumber
SimradSU90OperatorManual