User's Manual


GuardianManual001‐5006‐000Rev0 24|Page
TheinstallerofthisequipmentmustensuretheantennaislocatedorpointedsuchthatitdoesnotemitanRFfield
inexcessofHealthCanadalimitsforthegeneralpopulation.Recommendedsafetyguidelinesforthehuman
exposuretoradiofrequencyelectromagneticenergyarecontainedintheCanadianSafetyCode
6(availablefrom
HealthCanada)andtheFederalCommunicationsCommission(FCC)Bulletin65.
Anychangesormodificationsnotexpresslyapprovedbythepartyresponsibleforcompliance(inthecountry
whereused)couldvoidtheuser'sauthoritytooperatetheequipment.
2.6 TERRAINANDSIGNALSTRENGTH
Alineofsightpathbetweenstationsishighlydesirableandprovidesthemostreliablecommunicationslinkinall
cases.Alineofsightpathcanoftenbeachievedbymountingeachstationantennaonatowerorotherelevated
structurethatraisesithighenoughtoclearsurroundingterrainand
otherobstructions.
Therequirementforacleartransmissionpathdependsonthedistancetobecoveredbythesystem.Ifthesystem
istocoveralimiteddistance,say3‐5miles,thensomeobstructionsinthetransmissionpathmaybetolerable.For
longer‐rangesystems,anyobstructioncouldcompromise
theperformanceofthesystem,orblocktransmission
entirely.
Thesignalstrength(RSSI)atthereceivermustexceedthereceiversensitivitybyanamountknownasthefade
margintoprovidereliableoperationundervariousconditions.Fademargin(expressedindB)isthemaximum
tolerablereductioninreceivedsignalstrength,which
stillprovidesanacceptablesignalquality.Thiscompensates
forreducedsignalstrengthduetomulti‐path,slightantennamovementorchangingatmosphericlosses.CalAmp
recommendsa30dBfademarginformostprojects.
Table2.3showstheRSSIversusReliability.Table2.3RSSIReliability
RSSI Reliability
‐100dBm
Approximately 50% reliability. Fading may cause frequent data loss.
‐90dBm Approximately90%reliability.Fadingwillcauseoccasionaldataloss.
‐80dBm Approximately99%reliability.Reasonabletolerancetomostfading.
‐70dBm Approximately99.9%reliabilitywithhightolerancetofading.
2.7 RADIOINTERFERENCE
Interferenceispossibleinanyradiosystem.However,sincetheGuardianisdesignedforuseinalicensedsystem,
interferenceislesslikelybecausegeographiclocationandexistingoperatingfrequenciesarenormallytakeninto
accountwhenallocatingfrequencies.
Theriskofinterferencecanbefurtherreducedthroughprudentsystemdesignand
configuration.Allowadequate
separationbetweenfrequenciesandradiosystems.Keepthefollowingpointsinmindwhensettingupyourradio
system.
a. Systemsinstalledinlightlypopulatedareasareleastlikelytoencounterinterference,whilethoseinurban
andsuburbanareasaremorelikelytobeaffectedbyotherdevices.