AIS Receive Problem Identification

Rick D

Rick D

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Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I have a B&G multi-purpose display which will display AIS targets when fed from a Standard Horizon VHF with AIS receive capability. The last time I was at the boat, I noticed the AIS targets were not showing on the chart. I rebooted the unit, but no change. I rebooted the SH VHF and checked it's reception after a few minutes. It picked up about five targets set at the five-mile setting. The B&G showed three. There were at least a dozen commercial targets in that range. (Lots of fully-loaded container ships at anchorages waiting for dock space, a whole other subject.)
So, my mental analysis says antenna or feed/connector issue. It could be a connection between the SH & B&G too, but I think that's less likely because of what seemed to be fewer targets displayed on the SH that I expected. I have ordered an antenna analyzer. Thoughts?
 
Parsons

Parsons

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Jul 12, 2011
1,165
Leopard 40 Jupiter, Florida
To clarify, your black-and-white display on the VHF showed AIS targets, but they were not mirrored on the B&G display? Seems like the fault is between the VHF and the multi-display. What are your connections - NMEA what?
 
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jssailem

jssailem

.
Oct 22, 2014
21,104
CAL 35 Cruiser #21 moored EVERETT WA
Unsure why the SH is not picking up all of the possible targets you identify. That would lead me to think you have an:
  • Antenna,
  • coax,
  • or connection corrosion issue.
  • SH is filtering the AIS signal due to length of time vessel is stationary.
  • Signal from AIS land based repeater could be filtering AIS transmission - beyond your control
The lack of data showing on your MFD could be a couple of issues.
  • VHF not sending signal to B&G
  • Signal being sent not in correct format for B&G to understand
  • Data connections/wires have corrosion issues
  • B&G filtering contacts i.e. signal is stationary filter - check programing
 
D

dlochner

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Jan 11, 2014
11,425
Sabre 362 113 Fair Haven, NY
Are the ranges set to the same distance? If the VHF has its range at 10 miles and the MFD set to 5, ships in the 5-10 mile range will not show up on the MFD but will show up on the VHF.
 
Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Parsons said:
To clarify, your black-and-white display on the VHF showed AIS targets, but they were not mirrored on the B&G display? Seems like the fault is between the VHF and the multi-display. What are your connections - NMEA what?
Click to expand
There were about five targets on the VHF display, but three on the B&G. NEMA connection.
 
Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
jssailem said:
Unsure why the SH is not picking up all of the possible targets you identify. That would lead me to think you have an:
  • Antenna,
  • coax,
  • or connection corrosion issue.
  • SH is filtering the AIS signal due to length of time vessel is stationary.
  • Signal from AIS land based repeater could be filtering AIS transmission - beyond your control
The lack of data showing on your MFD could be a couple of issues.
dlochner said:
Are the ranges set to the same distance? If the VHF has its range at 10 miles and the MFD set to 5, ships in the 5-10 mile range will not show up on the MFD but will show up on the VHF.
Click to expand
  • VHF not sending signal to B&G
  • Signal being sent not in correct format for B&G to understand
  • Data connections/wires have corrosion issues
  • B&G filtering contacts i.e. signal is stationary filter - check programing
Click to expand
Agree in your assessment that if SH is not showing all the targets, it's most likely something in the antenna/connection/coax. I don't think the SH has target filtering; I'll have to look. However, your point about the B&G filtering the targets is well-taken. I think I changed the setting since there are so many commercial ships at anchor around me, I may have them filtered out if not moving. Before I tear things apart, I'm going to check that!
 
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D

dlochner

.
Jan 11, 2014
11,425
Sabre 362 113 Fair Haven, NY
Rick D said:
Agree in your assessment that if SH is not showing all the targets, it's most likely something in the antenna/connection/coax. I don't think the SH has target filtering; I'll have to look. However, your point about the B&G filtering the targets is well-taken. I think I changed the setting since there are so many commercial ships at anchor around me, I may have them filtered out if not moving. Before I tear things apart, I'm going to check that!
Click to expand
My B&G will drop targets when they are no longer a threat, i.e., heading away from me.
 
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Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
dlochner said:
Are the ranges set to the same distance? If the VHF has its range at 10 miles and the MFD set to 5, ships in the 5-10 mile range will not show up on the MFD but will show up on the VHF.
Click to expand
Interesting. As I recall, the B&G AIS target display is independent of the SH range selection. In other words, as I recall, the B&G would show targets to the limit of the receive range regardless of the range selection on the SH VHS. I'm going to check that tho. Thanks for the suggestion.
 
Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
dlochner said:
My B&G will drop targets when they are no longer a threat, i.e., heading away from me.
Click to expand
I don't think mine does, but, if I recall correctly, it's a setting. I'll check that too. Thanks for the note.
 
D

dlochner

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Jan 11, 2014
11,425
Sabre 362 113 Fair Haven, NY
Rick D said:
Interesting. As I recall, the B&G AIS target display is independent of the SH range selection. In other words, as I recall, the B&G would show targets to the limit of the receive range regardless of the range selection on the SH VHS. I'm going to check that tho. Thanks for the suggestion.
Click to expand
That's correct. The VHF radio will send all the data to the MFD, however, targets outside of the display range of the MFD will not show up. If the display range is equal to the VHF display range, then all targets should show. If the MFD display range is larger than the VHF display range then VHF should show fewer targets than the MFD.

If you have the SH 2200 Matrix with AIS, then the network connection is NMEA 0183. O183 is sensitive to transmission rates, the baud rate may have been changed which may limit the amount of data the VHF can send. Someone with more knowledge about NMEA 0183 might offer more insight.
 
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Davidasailor26

Davidasailor26

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May 17, 2004
5,079
Beneteau Oceanis 37 Havre de Grace
Rick D said:
I don't think mine does, but, if I recall correctly, it's a setting. I'll check that too. Thanks for the note.
Click to expand
There is a setting for that. In the Zeus it’s called “icon filters” in the Vessels part of the Settings screen. You can hide all, hide safe targets, hide over a specified distance, or hide under a specified speed.

There is also a network diagnostics screen that shows things like if any messages are being dropped and what the network loads are. That might help diagnose the issues if the filters don’t help.
 
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Brian D

Brian D

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Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
Well, Rick, sounds like you have a host of help here. I believe you are on the right path, just remember to not bounce back and forth between the radio and the MFD. Pick one and work you way to the other. When chasing rabbits, we select one rabbit and after catching that one, we move to the next rabbit. Not trying to catch all at one time.

When I trouble shot satellite systems, I used the 4P solution - Power (meaning electrical) / Pointing (is the antenna pointed at the correct satellite) / Parameters (are they set correctly) / Parts (what needs to be replaced). You will find you solution in one of these fields.

Good luck and I will be watching to see what was the issue. So don't forget to follow up with a detailed fix. LOL (Oh... and don't forget the beer, it helps finding the problem) :beer:
 
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Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Brian D said:
Well, Rick, sounds like you have a host of help here. I believe you are on the right path, just remember to not bounce back and forth between the radio and the MFD. Pick one and work you way to the other. When chasing rabbits, we select one rabbit and after catching that one, we move to the next rabbit. Not trying to catch all at one time.

When I trouble shot satellite systems, I used the 4P solution - Power (meaning electrical) / Pointing (is the antenna pointed at the correct satellite) / Parameters (are they set correctly) / Parts (what needs to be replaced). You will find you solution in one of these fields.

Good luck and I will be watching to see what was the issue. So don't forget to follow up with a detailed fix. LOL (Oh... and don't forget the beer, it helps finding the problem) :beer:
Click to expand
Excellent advice, Brian! I actually ordered the antenna analyzer at your suggestion, and the timing turned out to be perfect! I have two VHF antennas and a two band ham on the boat, so it will be handy there and at home.
 
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Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
UPDATE: it was the beer! This time, I checked all the settings in the B&G and found I was suppressing any targets under 2 knots. Something else too. Anyhow, I removed all filtering. I then shut the unit down. I turned on the SH and let it sit for about five minutes and then turned on the B&G and let it do the same. The targets showed well. I was concerned that they all showed the MMSI, but no names. However, I later saw some ID'ed by name. (You can see in the chart photos I took why filters are necessary where I am in the first place.)
I checked the antenna with my binoculars and all looked OK. I then asked for a radio check on 09 from some distance. I got a reply from a commercial ship in an outer anchorage. I also could hear Catalina Island Harbor Patrol about 25 miles out. I was receiving AIS targets out 20+ miles (3). So, I think all is well. I have not cruised the boat since August, what with all with all the COVID shut downs, so it was simply senility kicking in. This did remind me that I have all the hardware to integrate my Raymarine into my B&G, but I passed until I get better beer.
Thanks everyone for your help. It saved me a serious headache. Brian, I'm still going to use that antenna analyzer!
0109211129.jpg
0109211129.jpg
 
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jssailem

jssailem

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Oct 22, 2014
21,104
CAL 35 Cruiser #21 moored EVERETT WA
Good news Rick. :beer:

Sometimes we :banghead:then:facepalm:when the answers jump up and solve themselves.
:beer::biggrin:
 
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Richard19068

Richard19068

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Jun 11, 2004
1,633
Oday 31 Redondo Beach
Rick D said:
I was concerned that they all showed the MMSI, but no names. However, I later saw some ID'ed by name.
Click to expand
It seems to me over the last year or so many fewer commercial ships ( tankers and container ships) are showing their names in the San Pedro / Catalina channel . I just returned from a trip to Catalina and this was reconfirmed. MMSI but no name on maybe five out of six unfiltered targets. I don't know if I just thnk I remember most all showing the name in the past or I just have a faulty memory.
 
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Rick D

Rick D

.
Jun 14, 2008
7,139
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Richard19068 said:
It seems to me over the last year or so many fewer commercial ships ( tankers and container ships) are showing their names in the San Pedro / Catalina channel . I just returned from a trip to Catalina and this was reconfirmed. MMSI but no name on maybe five out of six unfiltered targets. I don't know if I just thnk I remember most all showing the name in the past or I just have a faulty memory.
Click to expand
Yes, I certainly remember more (most) having names. I wonder what's up with that? Maybe to avoid tracking? Also, destination and measurements also missing. It might simply be sloppiness in the system over the years.
 
D

dlochner

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Jan 11, 2014
11,425
Sabre 362 113 Fair Haven, NY
Richard19068 said:
It seems to me over the last year or so many fewer commercial ships ( tankers and container ships) are showing their names in the San Pedro / Catalina channel . I just returned from a trip to Catalina and this was reconfirmed. MMSI but no name on maybe five out of six unfiltered targets. I don't know if I just thnk I remember most all showing the name in the past or I just have a faulty memory.
Click to expand
If I recall correctly there are some limits on information being transmitted, with essential information being transmitted more frequently than other information. MMSI, location, speed and heading are sent more frequently than less important information, boat name, destination etc. There is a complex timing system that tells AIS transmitters when it is there turn to send information. Class A transmitters get higher priority than Class B.

An internet search will yield better answers, I don't have the time right now to pursue that.
 
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jssailem

jssailem

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Oct 22, 2014
21,104
CAL 35 Cruiser #21 moored EVERETT WA
This might help. It is from Marine Traffic.

help.marinetraffic.com

What kind of information is AIS-transmitted?

A functioning AIS transponder keeps transmitting information even when the subject vessel is anchored. The information contained in each AIS-data packet (or message) can be divided into the followi...
help.marinetraffic.com help.marinetraffic.com
What kind of information is AIS-transmitted?

@dlochner is correct. Not all data is transmitted all the time.
 
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