AIS Transponder (Transas, AIT 250, Comar)

[haydude]

I purchased the cheapest one, available on ebay UK at £385. There is no point to spend more for either an AIT 250 or a Comar. THEY ARE THE SAME THING although the Comar has a different case. Same electronic board, same firmware, same PC software configuration.

My experience so far has been disappointing.

I interfaced my unit with a Raymarine C80.

Devices: 1 x NMEA GPS (excellent quality), 1 x C80, 1 x Transas AIS transponder, 1 x DSC VHF radio
Mast antenna splitter using EasySplit OCB (no problem, verified no loss of signal and receiving range after install)

Phase 1: Everything integrated through a ShipModul AIS multiplexer. That is because I want position from my NMEA GPS. No way, C80 complains every few minutes of lost fix (never happened before).

Phase 2: remove multiplexer, get NMEA GPS through Raymarine Seatalk NMEA bridge on Seatalk. Did not solve the problem, still loss of fix from C80 every few minutes.
I though it must be because the transponder transmits at higher rate and takes priority.

Phase 3: leave NMEA GPS out and connect only transponder to C80, after all I still get the position. Again loss of fix every few minutes, but only when moving, not when stationary, which makes the issue very hard to debug. Now however I know that when that happens it is because the C80 has actually lost NMEA communications with the transponder, not because the transponder has lost fix. Problem still unresolved.
I ordered a Brookhouse multiplexer that can wipe GPS sentences from the AIS. I hope with that to solve the problem, but I will have to wait two more weeks.

Collateral issues discovered:

1) there is no support whatsoever for these transponders, for any. I tried with PrsComms that is the Transas dealer (do not know what to do) Transas (no answer), AIT (do not exist), and Comar (do not know what to do).
2) the configuration software is poor. There are no updates to date.
3) There is no way to disable the transponder from sending GPS data together with AIS on the NMEA link, so that one could use another, more reliable GPS receiver
4) Given that one is forced to using the transponder position and GPS data it would be nice if that were complete with HDOP and Satellite info. No way to configure the transponder to send that data permanently. There is a way to activate that using a PC, but when the transponder power is cycled, then the configuration is lost.
5) the firmware is pure rubbish with very few configurable options. The analyst who designed it should rather be a gardener with all due respect to the category. There are no firmware updates. If I think at the level of support we get for computer equipment much less expensive than this AIS transponder, and the inexistent support for this disproportionately (for the functions we get) expensive "marine" device, with such a poor quality firmware I only get INCENSED!

Conclusion, if you want to enjoy sailing rather than being annoyed by your plotter beeping all the time, do not buy any of these AIS transponders, or you will end up without the Chartplotter because YOU WILL TURN IT OFF!

 

[RAI]

Thanks for the warning, I was just about on the point of ordering an AIT250.

I suppose there's no way to inhibit the AIS outputting the GPS messages and to only output the AIS messages?

It seems to be a case for just an AIS receiver and a bigger radar reflector.

Or maybe to give the AIS transponder its own display.

 

[alan17]

Just a thought but would it help to give the C80 a position fix from a Raymarine GPS via seatalk? This would also give you a GPS back up.

 

[Ian_Edwards]

Hi,
I have an AIT250 plumbed in to an E80, the E80 has its own Raymarine GPS receiver and the AIT 250 uses its own GPS receiver, the AIT250 also provides GPS data to the ICOM DSC VHF. The AIT250 has its own Antenna near the top of the mast.
It's been running now for over a year.... no problems.
I've found the active AIS a useful addition to Mark One Eyeball and the RADAR (not a substitute). The classic example was sailing north up the Irish Sea last year from the Isle of Man to Bangor with about 2 miles visibility. We could hear the ferries, see them on the Radar and AIS, and see them alter course to avoid us. The fast commercial traffic could obviously see us on AIS? or RADAR? or both? We’ll never know. But using all the tools available see like the sensible option.
The Coast Guard can also see where you are ..... which you may or may not like!

 

[noelex]

[ QUOTE ]


Phase 3: leave NMEA GPS out and connect only transponder to C80, after all I still get the position. Again loss of fix every few minutes, but only when moving, not when stationary,

[/ QUOTE ]

A possible explanation of these symptoms is that the C series is not configured to accept the higher baud rate from the AIS gps. Worth a check anyway.
Cheers John

 

[Bejasus]

[ QUOTE ]
A possible explanation of these symptoms is that the C series is not configured to accept the higher baud rate from the AIS gps. Worth a check anyway.

[/ QUOTE ]
On the E80 you have to configure it to the higher baud rate for the AIS250 to function. I have Raystar GPS into the E80 and AIS out of the E80 at the higher baud rate which also feeds the Ray240 VHF. Use the multiplexer in the AIS250 box to output nmea180 into the Simrad Autopilot.

 

[Amphitrite]

Check your E80 if it is configured for NMEA input at 38400 baud. It sounds like the E80 can not keep up with the data speed. If that does not help, connect your NMEA GPS to the multiplexer and disconnect the AIT - does the E80 still loose the fix? If no, probably the NMEA output of the AIT is faulty...

 

[mixmaster]

I have the Comar transponer and have had no issues at all. Connected to a PC and Furuno display. The display/PC uses one GPS antenna and the AIS a second one. It shares masthead antenna with the VHF through an Easysplit unit. The Comar unit came with its own GPS antenna.
All works as it says on the tin.
Sent Comar an e-mailed question once and was answered.

 

[mikejames]

I have connected an Icom M505-AIS/GMDSS VHF (which only receives AIS) and a Garmin GPSMAP450S (postage stamp "chart"plotter) and I had an incident on Saturday.

All attention for a couple of minutes was on the little red blob on the chartplotter wondering why 'my boat' icon was red not green as usual and the answer came from 100m astern as the gas tanker signalled a turn to starboard to miss us.

I also have a Comar AIS-2 receiver at home, a superior unit to the ICOM M505/AIS as it is dual frequency, so it picks up much more data but sends it over NMEA at 38400 baud. The ICOM uses 9600 baud which is OK because it is scanning and AIS uses 9600 baud on each frequency.

It is not a good idea to filter out AIS data - there is a lot of it if there are a lot of ships around you.

An issue with the Comar unit is that the AIS output is true NMEA/RS422 differential rather than the sort-of-RS232 found on e.g. Garmin or the Icom. Connect only NMEA+ to the serial data in pin of a PC to get AIS data. And then the NMEA voltage output is quite small (3 volts) so not all PCs will take notice.

 

[haydude]

[ QUOTE ]
[ QUOTE ]


Phase 3: leave NMEA GPS out and connect only transponder to C80, after all I still get the position. Again loss of fix every few minutes, but only when moving, not when stationary,

[/ QUOTE ]

A possible explanation of these symptoms is that the C series is not configured to accept the higher baud rate from the AIS gps. Worth a check anyway.
Cheers John

[/ QUOTE ]
bits/s rate is OK, if that were the case, it would not communicate at all, instead communication is dropped (loss of sync?) every few minutes. I tried also at 4800 bits/s, does not make any difference. Cannot use intermediate rates marked on the C80 as Navtex because the C80 seems to filter out both GPS and AIS sentences.

 

[Ballistix]

I've got the AIT 250 and it works a treat. Hooked up to my Garmin 525s and it works perfectly. I've been told mast sharing is a definate no-no and you should use a dedicated mast for this.

T

 

[MikeCC]

1. What happens when the NMEA GPS Receiver only is connected to the C80? Does that maintain a fix?

2. When you have the transponder only connected, double check the baud rate is 38400. It is possible that some transmission will be successful using incorrect baud rate, although generally junk. (BTW Navtex and NMEA data are not the same format which is why they appear separately)

 

[hightech]

Have you updated to the latest version of C80 software, they are issues with earlier software and AIS

 

[haydude]

[ QUOTE ]
I have the Comar transponer and have had no issues at all. Connected to a PC and Furuno display. The display/PC uses one GPS antenna and the AIS a second one. It shares masthead antenna with the VHF through an Easysplit unit. The Comar unit came with its own GPS antenna.
All works as it says on the tin.
Sent Comar an e-mailed question once and was answered.

[/ QUOTE ]

That is not quite what I mean for an integrated system I am afraid. I prefer to have just one display with all the information getting to it, and I prefer to leave the PC at home.

 

[haydude]

[ QUOTE ]
I've got the AIT 250 and it works a treat. Hooked up to my Garmin 525s and it works perfectly. I've been told mast sharing is a definate no-no and you should use a dedicated mast for this.

T

[/ QUOTE ]

No true, I share the mast head antenna between the transponder and the VHF using an Easy AIS OCB splitter. No loss of signal on VHF, I have confirmation that my transponder's signal was received clearly at 9.5 miles distance.

Anyway that was not quite the problem I was reporting here. The problem was about interfacing the transponder with a C80 display (not E80) and the inability to disable the transponder from sending GPS information to the C80, and conflicting with the main GPS. I have since resolved the problem using a multiplexer with the ability to conditionally filter the unwanted NMEA sentences (brookhouse).

 

[haydude]

[ QUOTE ]
Have you updated to the latest version of C80 software, they are issues with earlier software and AIS

[/ QUOTE ]

Yes I did indeed. I also noticed that the C80 fails to display the base stations, displayed instead by the poor software supplied with the transponder. I reported the matter to Raymarine. I was actually surprised to receive a reply from them stating that they will work to modify their firmware to display also base stations. Once released you may thank me.
/forums/images/graemlins/smirk.gif

 

[haydude]

[ QUOTE ]
1. What happens when the NMEA GPS Receiver only is connected to the C80? Does that maintain a fix?

[/ QUOTE ]

Yes it does. No problem with the NMEA 0183 GPS

[ QUOTE ]
2. When you have the transponder only connected, double check the baud rate is 38400. It is possible that some transmission will be successful using incorrect baud rate, although generally junk. (BTW Navtex and NMEA data are not the same format which is why they appear separately)

[/ QUOTE ]

I did, definately at 38400. I can confirm also after further tests that it is not the transponder loosing fix, but rather the C80 loosing communications with the transponder. I tried both at 4800 and 38400 with the same results. Other speed selections are available on the C80, but 4800 and 38400 are the only settings accepting AIS and GPS data. The others seem to filter everything out and expect for Weather data.

I since resolved the problem with a Brookhouse multiplexer with conditional NMEA sentences filtering so that GPS data is received only by the main GPS talker.