Matsutec HP-33A AIS to Garmin alarm on own ship

[toucancatketch]

I have installed a new HP-33A feeding my Garmin GPS map 545s and using a vhf antenae splitter. The unit is working well displaying ais targets and AtoN data.

My problem is that at intervals I get a dangerous target for my boat on the chart plotter with my name and MMSI. The HP33A not show the alarm.

Looking at the nmea data stream I can see the aivdm sentence every time the alarm goes off. The HP33A sends aivdo often but the aivdm seems more random.

Has anyone seen this problem? It seems to me that with the splitter the transponder shouldn't be able to receive its own signal.
I'm doing this in a marina so could it be caused by some signal reflection?

I have contacted both matsutec/Huyang and Garmin but haven't gotten anything useful yet.

Thanks for any help.

 

[richvdh]

Better late than never, I can chime in to say I had exactly this problem. Likewise I failed to get anything helpful out of Hauyang or Garmin. As far as I can tell the HP-33A just reports its own position over NMEA, the same as it does any other vessel.

I ended up using an Arduino to filter out the NMEA sentences for my own boat. I put some details up at GitHub - richvdh/NMEAFilter.

 

[TSB240]

I believe there was a software update that overcame this problem. If you check back on other threads for the hp33 you may find it and how to apply it.

I used open cpn and just used the built in filter to eliminate displaying own boat as a target to eliminate the alarms.

It was interesting to see how quite often my transmitted ais boat position would lag the actual gps position by some considerable distance especially when in proximity to class A transmitters.

 

[KompetentKrew]

On B&G's Vulcan chartplotters you can set your own MMSI to avoid this exact problem. Page 96 of PDF manual Vulcan_OM_EN_988-10859-001_w2

 

[Yngmar]

Our HP-33a does this, but only once each time you toggle the AIS TX on/off. It's not an issue as we're using OpenCPN which can filter this (under Ships -> MMSI Properties -> Enter your MMSI -> Ignore this MMSI).

 

[Keith-i]

Interesting. I’ve experienced the same problem with a Digital Yacht AIT2000 and a Garmin plotter. Even more intriguing is that it’s only happened at almost the exact same point on a regular passage I make. I had noticed the range of my AIS transmission had reduced and found an aerial connection was slightly corroded. I’ve since replaced the aerial but not had the opportunity to see if this has made any difference to the collision warning.

 

[richvdh]

I believe there was a software update that overcame this problem. If you check back on other threads for the hp33 you may find it and how to apply it.

Interesting. I didn't find anything about this when I was searching, so if anybody has any links that would be helpful.