User Manual

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GuardianManual001‐5006‐000Rev0 21|Page
2.4 SITESELECTIONANDSITESURVEY
2.4.1 SITESELECTION
Forasuccessfulinstallation,carefulthoughtmustbegiventoselectingthesiteforeachradio.Suitablesitesshould
providethefollowing:
 Protectionfromdirectweatherexposure
 Asourceofadequateandstableprimarypower
 Suitableentrancesforantenna,interface,orothercabling
 Antennalocationwithan
unobstructedtransmissionpathtoallremoteradiosinthesystem
Theserequirementscanbequicklydeterminedinmostcases.
2.4.2 SITESURVEY
ASiteSurveyisanRFpropagationstudyoftheRFpathbetweentwopointsorbetweenonepointandmultiple
points.UHFradiosignalstravelprimarilybylineofsightandobstructionsbetweenthesendingandreceiving
stationswillaffectsystemperformance.Signalpropagationisalsoaffectedbyattenuationfrom
obstructionssuch
asterrain,foliage,orbuildingsinthetransmissionpath.ASiteSurveyisrecommendedformostprojectsto
determinetheoptimalRFpathsforeachlink.ThisisespeciallytruewhenmorethanoneRFcoverageareais
required.ASiteSurveywilldeterminethebestunitlocation
fortheRelayPoints.
2.5 SELECTINGANTENNAANDFEEDLINE
TheGuardiancanbeusedwithavarietyofantennatypes.Theexactstyleuseddependsonthephysicalsizeand
layoutofasystem.TheGuardiandevicehasbeentestedandapprovedwithantennashavingamaximumgainof
10dBi.
2.5.1 ANTENNAGAIN
Antennagainisusuallymeasuredincomparisontoadipole.Adipoleactsmuchlikethefilamentofaflashlight
bulb:itradiatesenergyinalmostalldirections.Onebulblikethiswouldprovideverydimroomlighting.Adda
reflectorcapableofconcentratingalltheenergyintoanarrowangle
ofradiationandyouhaveaflashlight.Within
thatbrightspotonthewall,thelightmightbeathousandtimesgreaterthanitwouldbewithoutthereflector.
Theresultingbulb‐reflectorcombinationhasagainof1000,or30dB,comparedtothebulbalone.Gaincanbe
achievedbyconcentratingtheenergybothverticallyandhorizontally,asinthecaseoftheflashlightandYagi
antenna.Gaincanbealsobeachievedbyreducingtheverticalangleofradiation,leavingthehorizontalalone.In
thiscase,theantennawillradiateequallyinallhorizontaldirections,butwilltake
energythatotherwisewould
havegoneskywardsanduseittoincreasethehorizontalradiation.
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