Simrad ST90 - Selecting Operating Frequency for Minimum Noise

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Basicoperatingprocedures,page37
Selectingoperatingfrequencyforminimumnoise
TheFrequencyfunctionisusedtocontrolthecentrefrequencyoftheacoustictransmissions
(pings).Thecentrefrequencycanbechangedfrom14to24kHzinstepsof1kHz.Alltypes
ofnoisematterwhenyouwishtondthebestoperatingfrequency.
Context
Alowerfrequencygivesyouabetterdetectionrangebecausetheattenuationlossissmaller.
Ahigherfrequencygivesyoubetterrangeresolution.Ahigherfrequencyalsogivesyou
narrowerbeamsanda"sharper"image".
Noisefrominternalandexternalsourceshaveanimpactonthechoiceofoperating
frequency.Onespecicfrequencymayperformbetterthantheothersonyourvessel.To
measurethenoiselevel,observethevaluepresentedontheNoisepageintheBITEdialog
box.
Werecommendthatyoudothistesttwice.First,dothetestwithallotherhydroacoustic
systems(echosounders,ADCP ,sonars)turnedoff.Second,dothetestwithnormal
operatingconditions.Thisallowsyoutoseehowtheotherhydroacousticsystemsaffect
theST90operation.
Procedure
1OntheMainmenu,selectUserSettings.
aSelectST90FactoryDefault.
bSelectActivateSelectedSetting.
cSelectOKtoapplyyourchangesandclosetheUserSettingsdialogbox.
2OntheMainmenu,setRangeto1000m.
3OpentheOperationmenu.SetTxPowertoOff.
4OpentheActivemenu.SetPulseTypetoCWMedium.
5OpentheSetupmenu.
6SelectBITEtoopenthedialogbox.
aSelectNoisetoopenthepage.
bSelectStartNoiseMeasurements.
SimradST90QuickStartGuide