Installing the AIS-CTRX unit

WARNING: Do not connect the AIS-CTRX unit to a mains (line) AC electrical supply, as an electric shock or fire hazard could result.

CAUTION: Do not connect the AIS-CTRX unit to a DC supply exceeding 15.6 V or reverse the supply polarity. Damage to the unit may result.

CAUTION: The AIS-CTRX unit is designed for operation in the temperature range -25 °C to +55 °C. Do not install (or use) the AIS-CTRX unit in environments which exceed this range.

CAUTION: do not install the AIS-CTRX unit in an environment where it can be subject to excessive exposure to water.

Electrical Connections

instalacionWarning: Only the RF, data and power cables provided with the AIS-CTRX unit should be used to connect antennas, power and display devices so as to maintain the integrity of the enclosure.

Please see the drawings section of this manual for details of the power, data and RF cables supplied

Remove the top of the transponder unit (eight screws) as shown.

Using the two co-axial leads supplied connect the down-lead from a VHF antenna to the VHF antenna port and connect the down-lead of a GPS antenna to the GPS antenna port. Please see Appendix A for recommendations on antennas and antenna installation.

If an external display unit (chart plotter, PC etc) is to be used connect the supplied power and data interface cable to the Power / NMEA port.

If an external display unit is not to be used connect the supplied power only interface cable to the Power / NMEA port.

Locate the RF, power and/or data cables into the rubber grommets pushing them firmly to the base of each slit. Each cable is pushed into the grommet slit which lies directly in front of the connector the cable is connected to.

Replace the top of the transponder unit taking care to seat the cable grommets and the lid seal correctly. Do not over-tighten the fixing screws.

If an external display unit is to be used (such as a chart plotter, PC serial terminal or other display device) connect the user end of the data interface cable to the display device. Note that the software in the display device must be configured for AIS operation AND to accept standard Class B operation NMEA sentences. This external display unit software is not part of the AIS-CTRX transponder package.

Connect a 12V DC supply (9.6-15.6V) capable of supplying 2A peak to the DC power lead (brown/red = positive, black/blue=negative).It is recommended that the supply voltage be SELV in accordance with EN 60950-1.

The case of the unit is not isolated from the negative terminal of the supply and therefore it is recommended that the unit is not attached to metal parts of the vessel.

Physical Mounting

It is recommended that the unit is attached to a solid wooden surface with 20mm M3 self tapping screws.A template for drilling pilot holes is shown on page 25.

Antenna Connections

GPS Antenna

This is a TNC female bulkhead connector mounted under the unit top cover.This port provides the 5V DC feed for the active GPS antenna required by the AIS-CTRX unit.

VHF antenna

This is a BNC female bulkhead connector mounted under the unit top cover.

GPS Antenna

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 25 dB should be available at the AIS-CTRX 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:

1.The GPS antenna is mounted in an elevated position and free of shadow effect from the ship’s superstructure

2.The GPS antenna has a free view through 360 degrees with a vertical angle of 5 to 90 degrees above the horizon.

3.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.

4.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.

VHF antenna for AIS use

The VHF antenna employed for AIS use:

  • Must be a dedicated antenna, i.e. not shared with any other VHF transmitter/receiver.
  • Must be suitable for marine shipboard applications (index of protection, ruggedness, means of mounting, etc.)
  • Should be omni-directional and vertically polarised 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.
  • Should be mounted with at least a two metre vertical separation distance from any other VHF antenna used for speech or DCS communication but see also the section “Radio Frequency Exposure Warning” below
  • Should be mounted at least 2-3 metres above sea level for full performance.

WARNINGS

VHF Antenna Connection

Connecting a badly mismatched VHF antenna, leaving the VHF antenna port disconnected, or shorting the VHF antenna port will activate the VSWR alarm, cause the unit to stop sending position reports or cause damage to the transponder.

Radio Frequency Exposure

To meet the requirements for Radio Frequency Exposure it is necessary to install the VHF antenna correctly and operate the AIS equipment according to the instructions.

The table below shows suitable safety distances to other equipment that could cause interference with the AIS Class B Transponder.

Object

Safety distance

Radar antenna, X-band

1, 5 m (5 ft)

High efficiency engines

1 m (3 ft)

HF or VHF antennas

3 m (10 ft)

AC power cables with high currency

1 m (3 ft )

Satelitcommunication antennas

4 m (13 ft)