True Heading AIS Transponder User Guide

Below you will find brief information for AIS Transponder. The AIS transponder is a device that allows your boat to be seen by other vessels equipped with AIS. It transmits your position and other information to other vessels, making it easier for them to avoid you. The AIS transponder is a valuable safety tool for any boater, especially in areas with heavy boat traffic.

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2012-06-04
Why can I not be seen/ Why cannot others see me at longer distances?
In order to explain why an AIS system is not working as you, and others, are expecting it to do (or if
you just want to program your AIS unit) you will need the software proAIS.
You will find the software here:
http://www.trueheading.se/files/document/products/ais/aisctrx/proAIS_3_76.zip.
Save the software on your PC (the software does not work with Mac) as the zipped (compressed) file
it is on the web site. Unzip the software and then install it on your PC.
Connect your PC to the AIS unit, start the software and connect your AIS to the software.
How do you actually know that you cannot be seen? I.e. what is the best way to control that you
actually can be seen by others?

The absolutely best way to control if you actually are sending your information out is to ask a
friend of yours who has a real AIS transponder (or AIS receiver) installed onboard and see if
he can see you in his nav. system.
However, there are some certain things you need to keep in mind when doing this test:
1. An AIS transponder is listening only the very first minute it has been powered up. It will
receive AIS information from others but it will take at least one minute before it actually
will send its own information out.
2. A Class B AIS transponder (independently what brand it is) will only send its dynamic
information out every 3rd minute if the boat is moving below 2 knots of speed.
This means that if you are lying still you will not send any position information or COG
and SOG information out until after at least 5-6 minutes after you have powered your AIS
system up. The general tip here is to wait approx. 15-20 minutes until you start looking
for faults in the system.
3. An AIS transponder (independently what brand it is and both Class A and Class B
transponders) only sends its static information out every 6th minutes (independent of
speed). I.e. you will not send any information out about the name of your ship, length
and beam, call sign etc. out until after at least 7 minutes after the unit has been powered
up. This means that you might be seen as a target in your buddy’s nav. system but he will
not see the name of your boat etc. until after at least 7 minutes.
4. The receiving AIS system might not have the greatest VHF antenna system on the planet.
This will of course affect the reception of signals in the receiving AIS system. If your
buddy&acute;s VHF antenna system is poor he might miss the first (and perhaps more)
transmission of data from you. If that happens it will take another 3 minutes (if you are
not moving above 2 knots) for him to receive the dynamic data and another 6 minutes to
receive the static data, and so on.
5. Has your buddy activated in his plotter that he actually shall see AIS targets in his
plotter? In some, actually most of, plotter/radar/charting software for PC you must go in
to the e.g. the sea chart page and “actively” say to the system that you want to see AIS
targets in this particular page.
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6. Is there any filtering activated in the receiving plotter/radar/charting software for PC
unit? In most of the plotter/radar/charting software for PC you can set filters that you
e.g. do not want to see AIS targets at certain distances, targets that do not move above a
certain speed etc. Make sure that these filters are turned off.
7. How far away are you from your buddy?
Keep in mind that the AIS system “works in the same way” as the VHF radio signals.
I.e. the only certain way to know that you can be seen is that there is a line of sight
between the sending VHF antenna and the receiving VHF antenna. If your antenna
”cannot see” your buddy&acute;s antenna, well, in general you shall not be seen by his AIS.
8. Are there any other filters activated in the receiving navigational system.
NOTE!!
The filters are activated and controlled from the application in which you are looking at
the AIS targets (e.g. plotter/radar/charting software for PC), NOT in the actual AIS unit
that received the information. AIS filtering cannot, nor is allowed, to be controlled in
the actual AIS unit (independently of brand of AIS system).

Another option to check whether you can, or cannot, be seen is to call up your local maritime
authority. Check if they can see you via their AIS/VHF base station antennas (which normally
have antenna heights that are very much higher than any mast on a boat).
Keep in mind as mentioned in #7, the AIS distance to be seen is still the line of sight between
a sending and a receiving VHF antenna. If you are in a bay, behind an island or behind any
kind of mountain, you probably will not be seen.

Can I check this via e.g. Marinetraffic.com?
In general “NO” if you would like to have an updated information in real time.
Read more about how the web sites such as Marinetraffic.com will get their information out
on the internet in the document “AIS and Internet_rev 1.1_120604” and that can be found
here:
http://www.trueheading.se/files/document/products/ais/aisctrxcarbon/AIS%20and%20Inter
net_rev%201.1_120604.pdf.
2012-06-04
FAULT FINDING:
General:
In order for an AIS transponder to be able to send its information out you must have:
1. A great VHF antenna with great cable and connectors.
2. A GPS antenna that is connected directly to the AIS transponder unit.
This GPS antenna shall be of an active kind that can be power supplied with 5VDC via the
coaxial cable (normally an RG-58 cable). This antenna is basically a “stupid” antenna that only
receives GPS signals i.e. the antenna will only receive GPS signals to the AIS unit and will not
send any kind of NMEA information to the AIS unit.
You cannot, and is not allowed, to use GPS information coming from e.g. a plotter.
3. An MMSI number that shall be programmed in to the AIS transponder unit.
You actually do not need the name of the ship/boat, call sign and approximate GPS antenna
position (from where we will get the length and beam of the ship/boat) on the boat in order
to send out AIS data. However, it actually is mandatory for everyone with an AIS transponder
unit to program the AIS unit with the name of the ship/boat, call sign, approximate position
of the GPS antenna on the boat and what kind of vessel it is.
Are the LED&acute;s lightning as they are supposing to?
The very first question when fault finding an AIS transponder is whether the top two green LED&acute;s
(Power and Status) are lit up.
If both of the LED&acute;s actually are lightning, but you still cannot be seen, everything is OK with the unit.
The problem, in 99% of the cases, is that you have a poor VHF antenna system (cables, connectors
and/or the actual VHF antenna).
To check how great your VHF antenna system actually is, connect the AIS unit to the PC, start the
software proAIS and go to the tab ”Diagnostics” and check the values after approx. 5-6 minutes.
2012-06-04
The proAIS-software reveals:
The VHF antenna.
When you have connected the AIS unit to the PC, started the software proAIS and connected the AIS
to the software you shall, after approx. 5-6 minutes, get values according to the document
“CTRX_end user_eng”. The document can be found here:
http://www.trueheading.se/files/document/products/ais/aisctrxcarbon/CTRX_end%2
0user_eng.pdf
IF, your values are deviating from the ones in the document ”CTRX_end user_eng” something is
wrong and you need to look your system over. If especially the value ”TX Reverse power” is to high
you are having to high standing wave ratio in your VHF antenna system.
This means that there is something wrong with your VHF antenna cable, connectors and/or VHF
antenna. Check the connections and/or run a new cable with new connectors direct from the AIS unit
to the VHF antenna and see if the values in the software changes.
You might also need to replace the VHF antenna with a brand new one and see what happens. If you
replace the antenna it does not have to be placed up high in order to see what happens with the
values (TX Forward and Reverse power) but keep in mind that you must not hold the antenna in your
hand while checking the values.
A general comment regarding the VHF system is:
“But, it works fine with my VHF radio. People can hear me and I can hear them”.
Well, that is possible and the reason is that with a VHF radio in general you will transmit with an
output power of 25W. A Class B AIS transponder (independently of brand) will send its information
out at 2W only which is 12.5 times lower output power as with the VHF radio. If the weakest link (the
VHF antenna system) should be bad in some way it will affect the power of the transmitted signal
considerably.
GPS antenna.
As mentioned earlier the AIS transponder must have a valid GPS position in order to be able to send
its information. Look under the tab “GPS status” in order to find out if the GPS in the AIS transponder
is working as it shall.
If the bars for the GPS signals are not as high as they should (above 30-40), or is none existing, check
the cables and connectors. As with VHF antenna, running a brand new cable with new connectors
between the AIS unit and the GPS antenna might be a good idea (to check whether it is the
cable/connectors, or not).
A replacement of the GPS antenna might also be something you might want to consider.
And of course, make sure that the GPS antenna is not obstructed from above.
MMSI number.
And of course, check so the AIS unit is programmed with the static data, and especially the MMSI
number under the tab “Static data”.
NOTE! The name of the ship/boat can only be entered with the letters a-z and you cannot enter signs
like “-“, “+”, “&amp;”, “/”, etc.
Other values:
The AIS transponder will not send its information, and will eventually go first to “Tx STAT” (yellow
LED) and then “Error” (red LED), if the internal voltage is below approx. 11VDC.
2012-06-04
Other things that might “affect the range”:
As mentioned before the AIS system is “based on the VHF system”.
This means that you must have a line of sight between the sending VHF antenna and the receiving
VHF antenna in order for these two antennas (AIS systems) to see each other. So, if your antenna
”cannot see” your buddy&acute;s antenna, well, in general you shall not be able to your buddy&acute;s AIS, and
vice versa of course.
”But, I can see other ships/boats behind capes and islands and at very far distances!”.
That is correct and that is thanks to atmospheric phenomena that make it possible to see at greater
distances and behind islands etc. Depending on the atmospheric phenomena the radio signals will
have different propagation and reach greater, or shorter, distances depending on e.g. the weather.
A clear, not too warm spring day, you will have the chance to “see” at very long distances.
A very warm summer day when it is pretty warm in the water you will ”see” at shorter distances due
to that the water evaporates and prevent the signals to travel at far distances.
In rain and fog the chance to “see” at far distances is the least – and that goes for a “regular” VHF as
well.
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Key features

Transmits position & info
Improves collision avoidance
Enhances safety at sea
Works with VHF antenna
Requires GPS antenna
Requires MMSI number
Supports software configuration
Provides diagnostic information
Includes LED indicators

Frequently asked questions

There are several reasons why you may not be seen by other vessels. It could be a faulty VHF antenna system, a lack of power, or incorrect configuration of your AIS transponder. The document provides a detailed checklist to troubleshoot these issues.

The range of your AIS transponder is dependent on the line of sight between your VHF antenna and the receiving antenna. It means you must have a clear view between the antennas to be seen by others. The document discusses the importance of antenna placement and how it affects visibility.

The best way to check if your AIS transponder is working correctly is to ask a friend with another AIS transponder to see if they can see you on their navigation system. The document also mentions the importance of using the proAIS software to help troubleshoot issues with your transponder.