Ships not detected by QK-A024

Quark-elec AIS receiver and NMEA MUX products questions

Ships not detected by QK-A024

Postby Martin » Sun Aug 06, 2017 9:07 pm

I had my QK-A024 on board my boat today and it seemed to work fine. I detected several vessels, but I noticed that one approaching and passing ship (offshore supply vessel) was not detected. Also a local "oil products tanker" moored in my harbour is not showing. I did check MarineTraffic when I came home for both vessels and MT have received signals constantly from hem today. Is there some AIS signals or messages that this receiver is not decoding or receiving correctly?
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Re: Ships not detected by QK-A024

Postby admin » Mon Aug 07, 2017 10:25 am

Hi Martin,

Do you have any records of this? Please send photos/screenshots of what it is you are trying to do so that we can assess what is actually happening to kit@quark-elec.com
Thanks
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Re: Ships not detected by QK-A024

Postby Martin » Sun Oct 29, 2017 9:06 pm

Are you still investigating what happened?
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Re: Ships not detected by QK-A024

Postby admin » Mon Oct 30, 2017 8:31 am

Hi Martin,
I was given to understand that was the case but it has been quite a long while now and I can understand why you would be frustrated. Could you send the unit back to me for testing? I can then send you a replacement.
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Re: Ships not detected by QK-A024

Postby Martin » Wed Nov 01, 2017 9:03 pm

I live in Norway so the cost of sending it back would probably be half the price of a new unit.
Have you decoded the log I sent and identified the vessels sending AIS signals? It may be that the unit is working and that the problem is my chart plotter. Decoding ship names and MMSI numbers from the messages I sent, should easily show where the problem is located.
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Re: Ships not detected by QK-A024

Postby admin » Thu Nov 02, 2017 2:36 pm

Hi Martin,

To answer your questions: Are there some AIS signals or messages that this receiver is not decoding or receiving correctly?No, as long as its standard NMEA 0813 format AIS messsages, it should be decoded.
It may be that the problem is with your chart plotter, some chart plotters can't decode all AIS messages. If you think this may be the problem we advise you to identify that using OpenCPN (free to download and use) on a laptop or android tablet to compare your results.

From the AIS log file, i can see there are at least 5 of AIS messages sent from MMSI 257587600, a few of them don't have the vessel name (for signal reasons), but all clearly show the MMSI number as 257587600 . This is why we think it may be your plotter to see if there is a reason why it hasn't been decoded.
Take one as an example. The message:
!AIVDM,1,1,,A,13maqT00000Ki0NShrBK4hl@0<1e,0*09
was decoded as:


Packet Type AIVDM
CHANNEL A
Message Type 1 Scheduled Position Report
Repeat Indicator Default
User ID 257587600
Navigation Status Under way using engine
Rate of Turn (ROT) Turning right at up to 708 degrees per minute or higher
Speed Over Ground (SOG)
Position Accuracy An unaugmented GNSS fix with accuracy > 10 m
Longitude 6.06551833333333 East
Latitude 62.5025216666667 North
Course Over Ground (COG) 283.5
True Heading (HDG) 26
Time Stamp 8
Reserved for regional Not available (default)
RAIM flag RAIM not in use (default)
Communication State 49261 Sync state: UTC Direct; Slot Timeout: 3 frames respectively are left until slot change; Received stations: 109
Communication Sync State Sync state: UTC Direct
Communication Slot Timeout 3 Slot Timeout: 3 frames respectively are left until slot change
Communication Sub Message 109
Communication Utc Hour No value
Communication Utc Minute No value
Communication Time Stamp No value
Communication Slot Number No value
Communication Received Stations 109
Communication Slot Offset No value

If you are still not receiving all the signals you think you should be receiving let us know.
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Re: Ships not detected by QK-A024

Postby Martin » Thu Nov 02, 2017 5:14 pm

Do you see the vessel with ID 257063600 in the log? It was located close to me when the log was recorded and according to Marine Traffic sending its position. This vessel is not showing up on my chart plotter.
Do you have a program where I can input the AIVDM NMEA message and get the output you showed in your previous message? Even better would be if it could connect to the QK-A024 directly and output the decoded information.
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Re: Ships not detected by QK-A024

Postby Martin » Sat Nov 18, 2017 3:52 pm

I found a web page where I could decode the NMEA strings and the ID for the missing ship was not in any of the messages. The only remaining possibilities are that the QK-A024 is not able to receive/decode/send out the messages or the vessel was not transmitting in the recording period.
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