Andrew Pace
Automatic identification systems, or AIS, can be used on boats to enhance safety. AIS works via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed, heading, name, port of origin, size, and draft, over VHF frequencies. AIS devices have internal GPS and some units have internal GPS antennas that may not work well below decks, so an external GPS antenna may be required. AIS can share the boat's VHF antenna and cable, or a dedicated AIS antenna can be mounted.
| Characteristics | Values |
|---|---|
| How it works | AIS works via a combination of GPS, VHF radio, and an AIS transponder. |
| What it transmits | Information about a ship's speed, heading, name, port of origin, size, draft, course, and current navigation status. |
| Antenna | AIS can have a dedicated antenna or share the boat's VHF antenna and cable. |
| Mounting | Lower radar-arch or pole mounts work but at the expense of range. |
| Cables and connectors | Cables and connectors must have no more than a 50% power loss. |
| Types | Class A, Class B, and Receive Only systems. |
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What You'll Learn
- AIS systems work in the VHF maritime radio band
- AIS transponders broadcast a ship's information, such as speed, heading, name, port of origin, size and draft
- AIS devices must be properly installed
- AIS antennas must be sited clear of other antennas and conductive materials
- AIS can share the boat's VHF antenna and cable
AIS systems work in the VHF maritime radio band
The AIS system works in the VHF maritime radio band, technically on what used to be channel 70. AIS uses a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed, heading, name, port of origin, size, draft, and more, over VHF frequencies 161.975 megahertz and 162.025 MHz. Commercial ships, ocean-going vessels and recreational boats equipped with AIS transceivers broadcast AIS messages that include the vessel's name, course, speed, and current navigation status.
AIS devices have internal GPS. Some AIS units have internal GPS antennas that can be helpful but may not work well below decks, so an external GPS antenna may be required. A dedicated AIS antenna is the most robust and reliable choice, providing redundancy and, usually, full operation of AIS and VHF simultaneously. However, in many cases, AIS can share the boat's VHF antenna and cable, which already has been installed for the VHF radio, by using a "low-loss" splitter.
Lower radar-arch or pole mounts work but at the expense of range. Mounting a dedicated AIS antenna is somewhat easier on a two-mast sailboat or on a powerboat where antennas can be spread out. Other antennas and conductive materials, such as sailboat shrouds and radar arches, will affect performance, so for best results, antennas must be sited clear of these. Getting the AIS "transmit" signal to the antenna and the "receive" signal back again requires good cables and connectors with no more than a 50-percent power loss.
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AIS transponders broadcast a ship's information, such as speed, heading, name, port of origin, size and draft
AIS, or Automatic Identification Systems, work via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed, heading, name, port of origin, size, and draft. This information is gathered by GPS and broadcast over VHF frequencies of 161.975 megahertz and 162.025 MHz.
AIS transponders are connected to a vessel's navigation system and automatically transmit updated information to other users in radio range. Commercial ships, ocean-going vessels, and recreational boats equipped with AIS transceivers broadcast AIS messages that include the vessel's name, course, speed, and current navigation status.
AIS devices have internal GPS, and some units have internal GPS antennas that may not work well below decks, so an external GPS antenna may be required. A dedicated AIS antenna is the most reliable choice, but in many cases, AIS can share the boat's VHF antenna and cable by using a "low-loss" splitter.
When installing AIS, it is important to consider the placement of the antenna. Other antennas and conductive materials, such as sailboat shrouds and radar arches, will affect performance, so for the best results, antennas must be clear of these obstructions.
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AIS devices must be properly installed
When installing an AIS device, it's important to consider the placement of the antenna. Lower radar-arch or pole mounts work, but at the expense of range. Mounting a dedicated AIS antenna is easier on a two-mast sailboat or powerboat, where antennas can be spread out. Other antennas and conductive materials, such as sailboat shrouds and radar arches, will affect performance, so for the best results, antennas must be clear of these.
Getting the AIS "transmit" signal to the antenna and the "receive" signal back again requires good cables and connectors with minimal power loss. While a dedicated AIS antenna is the most reliable choice, providing redundancy and full operation of AIS and VHF simultaneously, in many cases, AIS can share the boat's VHF antenna and cable by using a "low-loss" splitter.
AIS devices work via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed, heading, name, port of origin, size, and draft, over VHF frequencies. This information is gathered by GPS and transmitted to other users in radio range.
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AIS antennas must be sited clear of other antennas and conductive materials
AIS, or Automatic Identification Systems, work via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed, heading, name, port of origin, size, and draft, over VHF frequencies.
While a dedicated AIS antenna is the most robust and reliable choice, providing redundancy and, usually, full operation of AIS and VHF simultaneously, in many cases, AIS can share the boat's VHF antenna and cable. This can be done by using a "low-loss" splitter. However, this may be at the expense of range.
To get the AIS "transmit" signal to the antenna and the "receive" signal back again requires good cables and connectors with no more than a 50% power loss. This may sound like a lot, but with a 60- to 70-foot sailboat mast, that's about all you can get. It is important to note that all AIS devices have internal GPS, but some units may require an external GPS antenna if they are to work well belowdecks.
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AIS can share the boat's VHF antenna and cable
AIS (Automatic Identification Systems) works via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed and heading, the ship's name, port of origin, size, and draft, over VHF frequencies.
AIS works in the VHF maritime radio band, technically on what used to be channel 70. A full-function AIS transceiver is connected to the vessel's navigation system and automatically transmits updated information to other users in radio range. Commercial ships, ocean-going vessels, and recreational boats equipped with AIS transceivers broadcast AIS messages that include the vessel's name, course, speed, and current navigation status.
When installing AIS, it is important to consider the placement of the antenna. Lower radar-arch or pole mounts work but at the expense of range. Mounting a dedicated AIS antenna is easier on a two-mast sailboat or on a powerboat where antennas can be spread out. Other antennas and conductive materials, such as sailboat shrouds and radar arches, will affect performance, so for best results, antennas must be sited clear of these. Getting the AIS "transmit" signal to the antenna and the "receive" signal back again requires good cables and connectors with no more than a 50% power loss.
All AIS devices have internal GPS. Some AIS units have internal GPS antennas that can be helpful but may not work well below decks, so an external GPS antenna may be required.
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Frequently asked questions
AIS stands for Automatic Identification System. It is a system that works in the VHF maritime radio band, technically on what used to be channel 70. It is connected to the vessel’s navigation system and automatically transmits updated information to other users in radio range.
AIS works via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship's information, such as speed and heading (information gathered by GPS), the ship's name, port of origin, size and draft, and more, over VHF frequencies 161.975 megahertz and 162.025 MHz.
While a dedicated AIS antenna is the most robust and reliable choice, in many cases AIS can share the boat's VHF antenna and cable, which already has been installed for the VHF radio, by using a "low-loss" splitter.
