Specifications

Section-3 Operation
October 17, 2013
3‐36
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WARNING:Disconnectprimarypower priortoservicing. 888‐2693‐004
3.7.5.1 NonlinearCorrectionRangeSetup
Themodulatoroccasionallygeneratespeaksashighas18dBabovetheaverageoutputlevel.Thesignalpeakpower
abovetheaveragesignalpowerlevelcanbelimitedatthemodulatoroutputbypropersettingofthenonlinear
(correction)range.SincethislimitationtakesplacebeforetheRTACcorrectioncircuitry,onlythera
ngeofmagnitude
uptothislimitwillbelin earizedbynonlinearRTACcorrection.
Table3‐25XmtrHome>ExciterHome>Setup>DUC/RTAC>Nextx2
Field Explanation
PeakR
eduction
Control
On/Off:Pe
akReductionlimitstheRFpeakpoweroutputofthetransmittertoprovide
optimumRTACperformance,whi lepreventingnuisancetransmitterPAoverdrivetrips.In
mostcases,defaultsettingsshouldbeused.
Non‐Line
arRange(dB)
GreenifEn
abled.SetindB.Defaultvaluesaretypicallyused:
ATSC=7dB
OFDM=8dB
DAB=6dB
MaxCr
estFactor(dB)
MaxCr
estFactor(dB):SetindB.Defaultvaluesaretypicallyused:
ATSC=11dB
OFDM=13dB
Downconverter
BandpassFilter
On/Off:TheIFba
ndpassfilterintheRFdownconverterfiltersoutmixingproductsfrom
thedownconversion.Thisfilterhasaslightfrequencyresponseirregularitywhichaffects
thelinearcorrection.ForUHFchannelswithnoadjacentchannelsonthepost‐filter
feedback,thisfiltercanbeoff.Otherwisethisfiltermus
tbeon.
RTACPr
ofiles:Profilesareuse dtotunetheRTACforvariouslinearandnonlinearoperatingconditions.Profilechoicesfor
linearandnon‐linearcorrectionareavailable.ThecorrectprofilewillimproveRTACperformance.
Linear
Dropmenuandselect:Basic,Short,Long,Max,BasicOffset,ShortOffset,LongOffset,Max
Offset.
Nonlinear
Dropmenuandselect:Basic,BasicMemory,Profi le3,Profile4,High,HighMemory,Profile
8,Profile9.
ModeSelect
edafterACMainsLoss
Linear Linear:Dr
opmenuandselect:Bypass,Adapt,Stored
Nonlinear Nonlinear:Dr
opmenuandselect:Bypass,Adapt,Stored
LPURT
ACOperatingModesDuringPowerUp:WhentheLPUispowereddown,RTACcorrectionfortheAdaptandHold
modesislost,butthestoredRTACcorrectionsarenotlost.Atpowerup,thetransmittermustoperateuncorrectedfora
fewminuteswhil eRTACadapts.IfRTACpoweronmodeissettoSt
ored,andifanappropriatecorrectionsetuphasbeen
previouslystoredinmemory,theStoredcorrectionwillbeloadedintotheRTACAdaptandHoldcircuits.Thiscorrection
willthenbecomeavailablefortheLPURTACoffairHoldmodeorfortheAdaptmodeiftheLPUisontheair.
PowerOnLinea
rMode
TheRT
ACPowerOnLinearModeselectiongivestheoptionofhavingtheexciter'slinear
RTACcorrectionintheAdapt,Stored,orBypassmodewhentheexciterispoweredon.In
theStoredmode,RTACsettingsareobtainedfrompreviouslystoredvaluesfromoneofthe
filtersetsintheStoredCorr
ectionSetssubwindow.
PowerOnNonlinear
Mode:
TheRT
ACPowerOnNonlinearModeselectiongivestheoptionofhavingtheex citer's
nonlinearRTACcorrectionintheAdapt,Stored,orBypassmodewhentheexciteris
poweredon.IntheStoredmode,RTACsettingsareobtainedfrompreviouslystoredvalues
fromoneofthefiltersetsintheStoredCorr
ectionSetssubwindow.
FrequencyRe
sponseTilt EntervalueindB.