Saab R4-AIS Installation Manual

Also see for R4: Short Instruction guide Operator's manual

Contents

Saab R4-AIS Installation Manual Manual pdf 12 page image

Mounting Page 11Document id: 7000 108-011 A22.5 VHF antennaThe R4 Transponder shall be connected to a VHF antenna.The R4-AIS Shipborne Class A Transponder System, like any othershipborne transceiver operating in the VHF maritime band, maycause interference to a shipís VHF radiotelephone. Because AIS is adigital system, this interference may occur as a periodic (e.g. every20 second) soft clicking sound on a shipís radiotelephone. This effectmay become more noticeable when the VHF radiotelephone antennais located close to the AIS VHF antenna and when the radiotelephoneis operating on channels near the AIS operating channels (e.g.channels 27, 28 and 86).Attention should be paid to the location and installation of differentantennas in order to obtain the best possible efficiency. Specialattention should be paid to the installation of mandatory antennaslike the AIS antennas.So, installing the AIS VHF antenna is also a crucial part of thesystem installation. How and where you install your AIS VHFantenna and cable can greatly affect its efficiency.2.5.1 Antenna locationLocation of the mandatory AIS VHF antenna should be carefullyconsidered. Digital communication is more sensitive thananalogue/voice communication to interference created by reflectionsin obstructions like masts and booms. It may be necessary to relocatethe VHF radiotelephone antenna to minimise the interference effects.Installing the VHF antenna for AIS on a vessel is a compromisebetween the following items:• Antenna type• Antenna separation• Clear view of the horizon• Antenna height2.5.2 Antenna typeThe AIS VHF antenna should have omni directional verticalpolarisation providing 3 to 5 dBi gain.2.5.3 Antenna separationThe AIS transponders are using simplex channels at frequencies onthe high side of the marine mobile band (AIS channel A = 2087(161.975 MHz) and AIS channel B = 2088 (162.025MHz)). Thesechannels are close to the duplex channels used for shore to shipmarine communication. The AIS VHF antenna should be separatedas much as possible from the voice VHF installations used for maincommunication to avoid unnecessary interference.There should not be more than one antenna on the same level. TheAIS VHF antenna should be mounted directly above or below theshipís primary VHF radiotelephone antenna, with no horizontalseparation and with a minimum of 2 meters vertical separation. If it