ACR Electronics ACR-AIS-300 Manual De Usuario

 

 

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Y1-03-0222 Rev T4T4  

 

          2.4.1 Antenna connections 

 

 

This is a TNC female bulkhead connector that mounts to the back of the case.  This port  

 

 

provides the 5V DC feed for the active GPS antenna required by the NAUTICAST-B unit.  

 

 

 

 

 

 

This is a UHF female bulkhead connector that mounts to the back of the case.   

 

 

   

2.4.2 Antennas and Antenna Mounting 

 

The GPS antenna used must be of the active type (i.e. it should incorporate an LNA) and must 

 

be suitable for marine shipboard applications (index of protection, ruggedness,   means 

of 

 

mounting, etc.).  An antenna should be selected with a gain (in dB) depending on the length of 

 

cable   between the antenna and the AIS unit; after subtraction of cable and connector losses a 

 

minimum total gain of 20 dB should be available at the NAUTICAST-B unit GPS antenna 

 

connector. The GPS antenna to be used for AIS use must be a dedicated antenna, i.e. not 

 

shared with any other GPS receiver. Installation of the GPS antenna is critical for the 

 

performance of the built in GPS receiver which is used for timing of the transmitted time slots 

 

and for the supply of navigational information should the main navigational GPS fail.  

 

We strongly recommend that: 
¾  The GPS antenna is mounted in an elevated position and free of shadow effect from the 

ship’s superstructure. 

 

¾  The GPS antenna has a free view through 360 degrees with a vertical angle of 5 to 90 

degrees above the horizon. 

 

¾  As the received GPS signal is very sensitive to noise and interference generated by other 

onboard transmitters, ensure that the GNSS antenna is placed as far away as possible from 
radar, Inmarsat and Iridium transmitters and ensure the GPS antenna is free from direct 
view of the radar and the Inmarsat beam.  

 

¾  It is also important that the MF/HF and other VHF transmitter antennas are kept as far away 

as possible from the GNSS antenna. It is good practice never to install a GNSS antenna 
within a radius of 5 meters from these antennas. 

 
 

¾  The VHF antenna employed for AIS use: 
¾  Must be a dedicated antenna, i.e. not shared with any other VHF transmitter/receiver. 
¾  Must be suitable for marine shipboard applications (index of protection, ruggedness, means 

of mounting, etc.). 

¾  Should be omni-directional and vertically polarized with unity gain (0 dB) with a bandwidth 

sufficient to maintain VSWR <1.5 over the frequency range 156 – 163 MHz. As a minimum 
the 3dB bandwidth must cover the two AIS channels and the DSC Channel.  

¾  Should be mounted with at least a two meter vertical separation distance from any other 

VHF antenna used for speech or DCS communication but see also the section “Radio 
Frequency Exposure Warning” below.