Masterclock GMR5000 - GPS Antenna Cabling and Options; Antenna Cable Configurations and Options

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MasterclockGMRUserManualv2–2016.12
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WINDOWANTENNAPLACEMENT
Thewindowmountantennaissuitableforuseonlywiththenetworktime
serverproductswithappropriateversionsoffirmware.Forwindowmounted
antennainstallations,itisbesttouseawindowwiththebestviewofthesky.
Forwindowswithequivalentviews,orientationsthatfacetheequatorare
preferred.Generally,moresatelliteswillbeinviewtowardtheequatorthan
awayfromit,eastorwestfacingwindowswillalsowork.Polarfacingwindows
willalsoworkbutingeneralarenotpreferred.Windowsthathavethebest
viewoftheskyarealwayspreferredregardlessoforientation.
Attach
theantennaabovethewindowsillversusatthetopofthewindow.
Thiswillimprovetheupwardvisibilityfromtheantennatothesky.Notethat
somewindowglazingtreatmentsmayreduceorblocktheGPSsignals,
preventingthetimeserverfromacquiringthetime.
ANTENNACABLECONFIGURATIONS/OPTIONS
AntennacablingsolutionstypicallyvarydependingonhowfartheantennaisinstalledfromtheGPSreceiver.150
feet(45m)istheunaidedcablelengthlimitformanyGPStimingreceivers.AddingaGPSinlineamplifierextends
thecablelengthanadditional150feet(45m).Beyond300feet(90
m)alternativemethodsmaybeused.Figure3
highlightsthecablelengthsandtheantennasolutionsthatenablethem.
IN‐LINEAMPLIFIER
In‐lineamplifiersovercomesignalattenuationinbyamplifyingthe
GPSsignal,addinganadditional150feet(45m)incablelength.The
inlineamplifierattachesdirectlyinlinewiththeantennacableand
usesthesamepowerastheantenna;noextrawiringisrequired.
SeeFigure4for
atypicalmastmountapplication.
GPSDOWN/UPCONVERTER
TheGPSDown/Upconvertermakescablerunsof250to1500feet
(75mto457m)possible.GPSsignaldownconversionrequiresaspecialGPSantennaandcorrespondingsignalup‐
converter.Theantennamoduleconvertsthesignaldowntoalowerfrequencythatislesssusceptibleto
attenuation,andtransmits
itthelengthofthecableto
theup‐converter.Theupconverterrestoresthesignalto
thenormalGPSsignalfrequencyforthereceiver.The
down/upconversionprocessistransparenttotheGPS
receiver.AswithanyprecisionGPStimingreceiver,only
cabledelayanddownconversiondelaysneed
tobe
enteredintothereceiver.PowerissuppliedbytheGPS
receiver.InthecaseofBuslevelGPSreceiversanexternal
powersupplyisused.Itisimportanttonotethatthe
cableusedinGPSdown/upconversionisdifferentthan
thestandardcable.
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FIBEROPTICLINKS
Fiber‐opticconnectionsfunctionasatransparentlink
betweentheantennaandGPSreceiverequipment.These
linkseliminatethelimitationsofcoppersystemsby
enablinglongertransmissiondistanceswhileretainingthe
highestlevelofsignalquality.Inaddition,fiberoptics
provideseveralothersignificantnetworkadvantages,
includingsimplifiednetworkdesign,
easeofinstallation,
andimmunityfromEMI/RFIandlightning.