A021 dongle: No ship names for class A targets

[Anonymous]

Hi there !
I am using you A021 AIS receiver dongle together with Open CPN 4.6.1 and connected via Raymarine splitter to my mast VHF antenna (mast height 18m).
I can successfully see AIS class A and B targets in up to 18nm distance.

But for some reasons the vessel names for AIS class A targets are never shown. Only for class B targets. The heading and speed data etc. for AIS class A targets are always shown.
There is no setting option in Open CPN for this.

What is the problem? Hardware problem with your dongle? Software error at your dongle?

Thanks upfront for your assistance !

[Quark Elec]

Thanks for your information. The A021 will not be able to show some ship manes fro the following reason. QK-A021 has a single AIS receiver which hops between the two AIS channels alternately
The vessels’ name information will be in NMEA0183 message 5, which could contain multiple sentences. When the vessels’ names are packed in multi-sentence messages, hopping between two channels can incur a loss or some parts of some messages.When that happens the names may not be correctly decoded and thus will not show. There is also the chance that a message coming from one frequency while the receiver is listening to the other may also incur losses. More vital messages like speed, position, direction, and flag are all packed in single sentence AIS messages, which avoids this loss.
Hope that helps!

[Quark Elec]

QK-A021 V2.0 has been released in Jan 2018. Operator can setup the interval time through GUI software. Set the interval time as 30 seconds(this is the value used by most of other brand single channel AIS receivers), the shipping names should be recognized. Doing this you lost the advantage of picking up more AIS messages by Auto-hopping channels.

[Anonymous]

I have a V1.0 that I bought last fall. Is there any update I can use that will help me get ship names or any other changes I can make. i am using Polar View 3.0.4 on a window 10 laptop.

Thanks

[Quark Elec]

Hello

An update to our product won’t fix this. This is due to the AIS system working out how many vessels are in the area and then sends the most important information first in a single sentence. It will then transmit the rest of this information depending on the amount of vessels in the area and the importance.

The QK-A021 hops between the two channel frequencies of AIS. If it hops to another channel while a message containing a ships name is being sent on the other then the likely hood is it won’t receive that information. AIS is very clever in how it works. This won’t happen with the Dual channel devices we sell. However the ships name and length might not appear straight away as explained due to the way AIS is designed.

I hope this helps.

Best regards

[Anonymous]

Can the AIS system be modified to fix this though? Or is it straight up impossible?

[Quark Elec]

Hello

You will get this information eventually but it may take a while. with a single channel it could take even longer. i have taken an excerpt from the coastguard which may help clear things up as i know it can be hard to explain it sometimes.

11. Why am I unable to see an AIS vessels’ name or other static information (dimensions, call sign, etc.)? Shipboard AIS units autonomously broadcast two different AIS messages: a ‘position report’ which includes the vessels dynamic data (e.g. latitude, longitude, position accuracy, time, course, speed, navigation status); and, a ‘static and voyage related report’ which includes data particular to the vessel (e.g. name, dimensions, type) and regarding its voyage (e.g. static draft, destination, and ETA). Position reports are broadcasted very frequently (between 2-10 seconds-depending on the vessels speed-or every 3 minutes if at anchor), while static and voyage related reports are sent every six minutes; thus it is common and likely that an AIS user will receive numerous position reports from a vessel prior to receipt of the vessel’s name and type, etc. Note, the U.S. Coast Guard operates a Vessel Information Verification Service which can be used to not only verify that an AIS has broadcasted, but, will also provide certain AIS static data (i.e. MMSI, name, call-sign, IMO number, vessel type, draft, dimensions, and positioning source) and highlight any potential data or encoding discrepancies (contrary to our USCG AIS Encoding Guidance) the vessel may have.

I hope this helps.

[Author]

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