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Section-5 Maintenance

October 17, 2013

5‐16

WARNING:Disconnectprimarypower priortoservicing. 888‐2693‐004

5.5.1.1 TroubleshootingPrecorrection

IftheRTACmodearesettoADAPT,buttheAttemptscounterdoesnotincrementwithinthirtyseconds,thereisa

problemwiththefeedbacksamples.

Checkthesignallev

elsatthePREandPOST‐FILTERinputsonthebackoftheLPU.Theyshouldbebetween‐10dBm

and+5dBm(optimumis‐5dBmattheinputsonthebackoftheLPU).

ChecktheRT

AClevelsontheLPUSTATUS>RTACGUIscreen.Thebarmetersshouldbegreenandthelevelshould

bejustbelowtheblack100%line.

Checktha

ttheExciterHomescreenshowsONintheup perleftcorneroftheGUIscreen.IftheexciterisOFFor

MUTE,thecorrectionscannotbecalculated.

5.5.2 StoringPrecorrection

FollowthisproceduretostorethecalculatedRTACcorrectionvaluestoLPUmemory.

STEP 1

GototheRTAC‐StoredCorrectionsetsScreen,Figure5‐8onpage5‐16.

Figure 5-8 RTAC Stored Correction Sets Screen

STEP 2

Enteranameofuptosixteencharactersforthedesiredset.

STEP 3 PresstheSAVEbuttontostorethecorrectiontomemory.

Note

The correction currently being applied will be stored, overwriting any values previously stored in mem-

ory.

STEP 4

Endofprocedure.

5.5.3 RTACSetupandOperationinCombinedSystems

HarristelevisiontransmissionsystemsuselinearRTAC(RealTimeAdaptiveCorrection)tocompensatefordistortions

producedbytheoutput maskfilter.Single transmittersystemsuseaforwardpowersample,takenfr omadirectional

couplerafterthemaskfilterthatissentbacktotheexciterviacoaxialcable.Thesample(‐5dB

mlevelisnominalfor

M2Xexciters,LPUs,andCCD‐LPUs)isusedtoproducepre‐correctionwhichisappliedtotheexciteroutput.Thus,

theexciteroutputispre‐distortedtocompensateforthedistortionsproducedintheoutputmaskfilter.Single

transmittersystemsnormallyoperatewithRTACcorrectionssettoAdap

tmode.Preandpost‐filterRTACsample

levelsshouldbewithin1dBofeachother.

Multipletr

ansmitters(atdifferentchannels)canbecombinedintoacommonantennausingacombinersystemas

showninthesamplesketchbelow.

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