Masterclock GMR1000 - GPS Lock Issues and Troubleshooting; Problems and Solutions

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MasterclockGMRUserManualv2–2016.12
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GPSLockIssuesandTroubleshootingTips
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Masterclockhighlyrecommendsusingonlythepre‐made/pre‐testedantennacablesprovidedbyMasterclock,Inc.
Forbestperformance,itisbesttoorderthesecablesatthesametimethatyouorderyourGMRwithGPSoption
installedasthismeanstheunithasbeenfactorytestedasasystem
withtheantennacablesandantennabefore
shipment.
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TheGMRwithaGPSmoduleinstalledrequiresapre‐amplifiedantenna.TheGMRprovides+5VDCviathecenter
pinoftheSMAcoaxialcable/connectorforremotepowertotheantenna.
GPSLOCKRELATEDISSUESANDTROUBLESHOOTINGTIPS
ThefollowingproblemsarespecifictotheGMRwithGPSoptioninstalled.Theseshouldbeconsideredonlyafter
the25‐minutesatelliteacquisitiontimehaselapsed.
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PROBLEMS:
 UnitisnotlockingtoGPS
 TheLEDonthefrontpanelisblinkingtwicepersecond
 Unitisnotservingtime
 WinDiscoverydisplaysnoGPSsatelliteinformation
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SYMPTOMS,REASONSANDSOLUTIONS
FLASHONCEPERSECOND:ThereferencelockLED(green=locked)willflashoncepersecondwhenlockedtoGPS.
VerifytheactivereferenceusingdevicestatusavailablewithWinDiscovery,SSH,ortelnet.
FLASHTWICEPERSECOND:ThereferencelockLED(green)willflashtwicepersecondwhenfreewheeling(running
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withoutexternallock,referencefrominternaloscillator).
TheGMRmustfirstacquireaninitiallocktoGPSbeforeitwillserveaccuratetime.Oncelocked,theunitcan
continuetoservetime(eitherwhilelockedtoGPSorwhilefreewheeling)aslongastheDCinputpowerisnot
interrupted.
Someprocedurestoconsider:
1. Waitatleast20to30minutesifinstallingtheGPSreceiverdeviceinanewlocation.TheGPSreceiver
mustfindandacquirethesignalfromatleastfourGPSsatellitessimultaneouslyandwillcontinueto
acquireuptotheeightsatellites.Whenplacedin
anewlocation,timetofirstlockcanbequitelengthy
sincethereceivermustupdateitsinternalalmanacandephemerisdatafromthesatellitesignals.
2. MakesuretheGPScablesandconnectorsarenotdamagedandthethreadedconnectorsaretightly
coupled.
3. RelocateandreinstalltheGPS
antennaoutdoorswithaclear/unobstructedviewofthesky.Finda
rooftoporsimilarlocationsuchasalargeopenfieldorparkinglotwithanunobstructedview.Whilethe
GMRmaylocktoGPSonsomeoccasionswiththeantennalocatedindoorsnearawindow,suchuseisnot
recommended.
YourGPSantennamustnotbenearsatellitedishesorsourcesofRFinterference,suchas
transmittersorotherantennas.
4. Replaceyourcableandconnectors.Yourantennacableorconnectorsmaybeshortedoropen.
5. Checkyourcablelength.Youmaybeusingtoolongofanantenna
cableorusinganimproperimpedance
cable.Ifnecessary,removethelongantennacableandconnecttheGMRdirectlytotheshortcableonthe
GPSantennausingtheshortSMAmaletoSMAmaleadapterprovidedwithyourantennapackage.
PreferredandtestedGPSantennacableisavailablefromMasterclock
inlengthsupto500feet(152m).