AISnode – Receiver

An AIS which sends and receives data is known as a transceiver (or often called a transponder). There are also simple devices called AIS receivers which pick up transmissions and decode for displaying on a compatible chart plotter or PC based navigation system – or even an iPad or tablet.

AIS transponders will allow you to receive data from vessels close to you, but will also allow you to continuously transmit your vessel’s identity, position, speed and heading, as well as other relevant information, to all other AIS-equipped vessels within your range.

To transmit its position, an AIS transponder must have its own GPS antenna. All our AIS transponders are supplied with a GPS antenna or have a built-in GPS antenna.

With an AIS receiver or transponder, you will receive all information of surrounding ships and will allow you to contact them directly. There are 3 types of AIS data that are automatically and continuously transmitted:

• Dynamic data: position and speed which are automatically calculated by the transponder.
• Static data: MMSI, ship name, size and contact details. This data is programmed on the device.
• Voyage data (only for class A transponder): Destination, ETA, number on board and navigation status. This data is programmed on the class A transponder before and during each voyage.

The data transmission frequency is different depending on the transponder category and the speed of the ship.

The AIS targets can be displayed in different ways:

• On a multifunction plotter/screen using the NMEA interface of an AIS receiver/transponder.
• On a PC/MAC navigation software thanks to a NMEA/USB adapter or an AIS receiver/transponder with an integrated USB interface.
• On an iOS/Android navigation application via a NMEA to WiFi server or an AIS receiver/transponder with integrated WiFi interface.

Each system will display the AIS targets differently (colours, size, etc.) but the data will remain the same. The next tab will explain which AIS transponder you need depending on the system you want to use to display the AIS targets.

If the AIS transponder doesn’t have a built-in VHF splitter (i.e. AIT5000), there are 2 options: either install a dedicated VHF antenna for AIS or install an antenna splitter so that the main VHF antenna is used for both VHF radio and AIS.

For those who want to use their existing VHF antenna, then we recommend the use of a certified zero loss VHF antenna splitter such as our SPL1500 and SPL2000. Please do not use a non-zero loss certified VHF antenna splitter. They are inexpensive, but they can destroy your AIS transponder.

For those who want to install a VHF antenna dedicated to AIS, then we recommend a VHF antenna tuned to AIS frequencies. The AIS transmission and reception works on 2 dedicated channels which use the frequencies 161.975 and 162.025 MHz (channel 87B and 88B). VHF frequencies in the maritime environment use frequencies from 156.0 to 162.025 MHz and most VHF antennas are designed to provide maximum gain on channel 16 (156.8 MHz). You can now find antennas on the market dedicated to AIS frequencies such as the HA156 antenna.

These antennas, dedicated to AIS frequencies, offer maximum gain at 162 MHz (which is the centre between the 2 AIS frequencies 161.975 and 162.025 MHz). So if you install a VHF antenna instead of a VHF antenna splitter for your AIS receiver or transponder, then choose an AIS frequency VHF antenna to compensate for the loss due to the installation of the antenna lower down than the main VHF antenna at the top of the mast. The graph below shows how a dedicated AIS frequency antenna (162 MHz) provides a better VSWR and therefore a better transmission and reception.

The best option would be to output the AIS information to a computer, most of our products now come with a USB connection as standard, so it is a simple plug and play connection to your computer.

Alternatively, you can add our WLN10/WLN30 to the AIS receiver and receives AIS targets directly on a navigation app. There are hundreds of apps which can display AIS targets.

No, we supply a version of our Smartertrack software free with every AIS product. The same software can also be upgraded at a later point to a full function navigation package with Navionics charts.