Specifications

Maxiva UAX
October 17, 2013
3‐37
888‐2693‐004 WARNING:Disconnectprimarypower priortoservicing.
Copyright©2013,HarrisBroadcast
Note
If this limit is too low, in-band and out-of-band intermodulation products will increase due to the signal
clipping. If the limit is too high, the RTAC nonlinear corrector performance may be degraded due to high
peak stretch. Also high peaks could cause nuisance overdrive faults in some transmitter systems.
STEP 1 Inthe’RTAC’SetupScreen1,onleftFigure3‐34onpage3‐33,setRTACLinear
andNon‐Linearfunctionsto’Bypass’.
STEP 2 TheRFoutputshouldbesettothelevelrequiredfortransmitteroperation.
STEP 3 IntheRTAC‘PeakReduction’subwindowofRTACSetupScreen3,onleft
Figure3‐35onpage3‐35,ve
rifythattheNon‐LinearRangeandMaxCrest
Factorindica
torsdisplay‘Enabled’.
STEP 4 IntheRTAC’PeakReduction’subwindowstartwiththeNon‐LinearRangeat
thedefaultvalue.SeeTable3‐25onpage3‐36.
STEP 5 WithbothRTACcorrectorsbypassed,theexciterRFoutputadjacentchannel
noiseshouldbe50dBto55dBbelowtheinbandsignallevel.
AstheNonlinear(Correction)Rangevalueisreduced,thefirstsignofadjacentchannelintermodulationproduct
increasewillbeverysubtle,withthefirstsignoftenbeingincreasednoiseintheareajustoutsidethein‐band
channelbandpass
TheRT
ACnonlinearcorrectoroccasionallygeneratespeaksashighas18dBabovetheaverageoutputlevel.
Therefore,thepeakpoweroutputfromtheexcitermustbelimitedinordertoprotectthefollowingamplifierstages.
STEP 6
Endofprocedure.
3.7.5.2 MaxCrestFactorSetup
TheMax(Maximum)CrestFactorsettinglimitsthepeaktoaverageRFoutputpowerratio(7.8to17.8dB)atthe
outputoftheex citer.ThisdirectlylimitsthetransmitterRFoutputpeaktoaveragepowerratio.TheCrestFactorof
thetransmittedsignalisdeterminedbythissettingandbythepeakc
ompressionoftheamplifiersystem.
• Ifthelimitissettoolow,clippingwillgenerateout‐of‐bandintermodulationproductsintheex citer’soutput
andmayaffecttheperformanceoftheRTACnon‐linearcorrection.
• Ifsettoohigh,itcouldallownuisanceover drivetripsinsometransmittermodels,becausethehighampli‐
tudepe
akscouldoverdrivethePAmodules.
Nuisanceov
erdrivetripscanbeavoidedbysettingtheMaxCrestFactorparametersectionoftheRTACPeak
ReductionsubwindowinRTACSetupScreen3,onleftFigure3‐35onpa
ge3‐35.
Nuisanceover
drivetripswilltypicallyoccurwithin30minutesto1houraftertransmitteroperationwithRTACisfirst
started.Ifthishappens,performthefollowing:
STEP 1
Thissetupisperformedwiththetransmitteroperatingatfullpowerand
RTACLinearandNon‐LinearfunctionssettoAdapt.
STEP 2 StartwiththeMaxCrestFactoratthedefaultvalue.SeeTable3‐25on
page3‐36.
STEP 3 ReducetheMaxCrestFactorby0.2dB.
STEP 4 Waitforonehourtoseeiffurtheroverdrivetripsoccur.Iftheydo,reduceby
another0.2dB.
STEP 5 Repeatsteps3&4untiloverdrivetripscease.
STEP 6 Excessivereductionwilleffectthelinearitycorrectionofthetransmitter.
AfterMaxCrestFactorhasbeenadjusted,observetheadjacentchannel
responsetoensurethatitstillexceedsthetransmitteroutputsignalmask
requirements.
STEP 7 Endofprocedure.