Basic Guide to AIS Receivers

The question we get asked most often

“I want to install AIS on my boat – what do I need?”

The type of AIS system you use on your boat depends on a number of factors:

The size of your boat (& the legal requirements)
Where you are going
What you would like to know
What other equipment you have on your boat. (Chartplotter, Type of Aerial, etc.)

Our basic guide to AIS Receivers will take them in turn and (hopefully) help you decide on the best AIS option for your boat.

1 – How big is you Boat?

i.e. do you need a Transponder or an AIS Receiver..

The size of your boat (and what you use it for) will affect

If you need to get a transponder (which sends our signals)
Or an AIS receiver – which will show you which boats are in your neighbourhood & where they are going.

1a. So, will you need a Transponder?

A transponder is designed to send out a signal showing the type of boat you are, where you are, your speed, direction, etc. A key element in the decision process is that there are strict rules and obligations as to which ships need them

Is your boat

Over 300 Gross Tonnes ? (For example a cargo ship, etc.)
A commercial boat using European Inland Waterways
EU fishing boat over 15 m
Commercial boats carrying passengers

In that case you will need to have a Class A type AIS transponder. Which sends out signals, so that you can be spotted. This broadcasts information every 2 to 10 seconds when moving (and every 3 minutes when at anchor)

A transponder provides information like how fast it’s going, where it’s going, the exact position, type of ship, name of the ship, etc. You should be able to receive this information up to 20 or 30 miles away.

If it’s smaller

Then you don’t need a Class A type responder but you might want to use a Class B type AIS transponder voluntary.

For example if you have

A sailing boat or yacht ?
Small fishing vessel, etc. ?

Class B transponders have a smaller range (about 5 to 7 miles) and will broadcast less often.

For example if a boat is going at less than 2 knots it will broadcast only every 3 minutes or every 30 seconds if going faster.

1b. Will you need a AIS Receiver?

If you have a transponder then this will also receive AIS information.

But even if you have a smaller boat..

Then a key advantage of an AIS receiver is that it will help you avoid other boats and depending on the type also show where you are in comparison with other boats. But the type of AIS receiver you will need will depend on where you are going and what you would like to know.

2 – Where are you going?

An AIS receiver is ideal for helping you avoid other boats & ships – as well as knowing ‘who is about’ if you get into trouble.

There is an obvious difference between shipping in the middle of the English Channel ‘rush hour’ compared to the peacefulness of the mid-Pacific Ocean.

But the advantage of an AIS receiver for your boat will be:

If you are ‘near the coast’ you will be able to ‘see around the corner’ or what’s behind the huge tanker,
As well as spot boats coming around peninsulas, moving out of harbours, etc.
Spot boats in all weather conditions (such as fog, poor visibility, etc.)
You will know who’s about if you get into trouble
Know where the coastline is, even in the dark. (In places where there are coastal AIS stations)

3 – What would you like to know?

A key consideration will be: How much information would you like, how quickly & how detailed?

3a. Single or Dual Channel Receiver

When a ship sends out AIS signals it will use 2 VHF radio frequencies – either at 161.975 MHz (AIS1, or channel 87B) and 162.025 MHz (AIS2, or channel 88B).

When it comes to AIS receivers there are 2 options – a single or a dual channel receiver.

All this simply means is that a single receiver can only receive the information from one of these channels at a time. Whereas a dual channel receiver will receive it from both at the same time.

This means a dual channel receiver will have more information than a single receiver.

For example:

At rest (or slower than 2 knots) a single one takes 6 minutes compared to 3 minutes for a dual channel one
At speed a single one takes 1 minutes compared to 30 seconds for a dual channel.

If you are in a location where most of the ships are larger (sending out the stronger Class A signal) this might not be a problem for you.

On the other hand, if you are in an area with smaller ships (possibly using the voluntary weaker Class B signals) this could be a problem as your system is not updated as quickly.

A dual channel receiver will also include complete messages whereas single channel receivers can miss some parts of the messages.

3b. How far away do you want to see?

Yes, your receiver will affect how much information you receive. But as a very ‘simple rule of thumb’ the higher your aerial the greater the distance ‘you can see’.

As a very rough estimate ships sending out Class A signals you will be able to see 20 to 30 miles away, and Class B signals about 5 to 7 miles.

3c. Do you want to see your location in relation to other boats?

When your AIS receiver gets the information it will ‘convert’ this into data to be used on equipment like a computer, laptop, chart plotter, etc.

You have the option to use information in 2 ways:

Either simply knowing who is about & where (How fast they are travelling, which direction, etc.)
Or combine this with your boats own position (Using GPS data)

4. So, what AIS Receiver will you need?

Partly it depends on how much detail you would like, but also what other equipment you have on your boat.

When you get the signals they need to be converted into a format you can use, but if you have other equipment on board they also need to be compatible with that format.

A bit like linking an Apple to a Microsoft system – it can be done but you need the right software to make it work.

There tend to be a variety of systems used on Marine Equipment (such as NMEA, Seatalk, etc.) and the right AIS receiver is able to combine the right equipment to give you easy to use information.

How to Start

A basic AIS system is as easy as plugging in a couple of cables and switching on the plug.

The advantage of most AIS receivers is that you can simply ‘plug them into’ an existing VHF Antenna (which most boats already have for radio communication). All you need to do is to buy a ‘splitter’, which then lets you use the antenna for both the existing radio communication as well as collecting the AIS data.

A Basic AIS Receiver?

For a basic AIS receiver all you will need are:

A standard marine VHF antenna
A laptop you can plug the AIS receiver into
A power source (although some can be powered through the USB port on the laptop)

Such as the QK-A022 AIS Receiver

Or something a bit more complex?

But if you want something a bit more complex:

Then you will need the above as well as:

A ‘splitter’ if you use the aerial for other uses (such as communication)
An AIS receiver that can ‘communicate’ with other items (such as a chart plotter) in their own language (like Seatalk, NMEA)
A receiver that can combine AIS with other data and communicate wirelessly to wired devices, etc.

Such as the QK-A026 AIS Receiver

Not sure what you need ? :

Hopefully our basic guide to AIS receivers has provide background information.

Our comparison chart will show you in more detail which AIS receiver to use & when – more details.