User's Manual

16 | P a ge
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DIAGNOSTICSGUIDE
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TheBDAprovideslongterm,care‐freeoperationandrequiresnoperiodicmai ntenance.Th ereareno
user‐serviceable components inside the BDA. This section cove rs possible problems that may be
relatedtotheinstallationoroperatingenvironment.
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GainReduction
Possiblecauses:BadRFcablesandRFconnections toantennas,damagedantennas.
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OccasionalDrop‐outofsomeChannels
Possiblecauses:OnechannelwithverystrongpowerdominatestheRFoutputoftheamplifi er.
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ANTENNASEPERATION
BDAoscillationiscausedbylowisolation(antennaseparation)betweendonorantennaandservice
antennas.Therecommendedisolationbetweenthoseantennasis15dbabovethesystemgain.The
amountofisolationthatcanbeachievedbetweenantennasdependsonseveralfactors,suchasthe
physicalverticalandhorizontalseparation(distancebetweentheantennas),pol
arization,radiation
patternoftheantennas,themediumbetweentheantennas,antennagainetc.
Antennaisolationcanmostaccuratelybedeterminedthroughon‐sitemeasurements Anantenna
isolationmeasurementconfigurationis illustratedinFigure6,wheretwospatiallyseparated
antennas(serviceantenna#1anddonorantenna#2)areconnectedtoasignalgen
eratorandsignal
analyzer.
Asignalatcenterfrequencyisgeneratedby thesignalgeneratorsenttotheinputofantenna1;the
outputofthesignalatantenna2ismeasuredandrecordedbythesignalanalyzer.Withcalibrated
connectioncables,bytakingintoaccountthecableloss,thediffer
enceofsignalpowerlevelatthe
outputofantenna2andthatattheantenna1inputistakenasantennaisolation.
(SeeAppendix2foranalyticalcalculation )
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Figure 6