Panbo

AIS Class B in the USA, just "a matter of weeks"

... written for Panbo by Ben Ellison and posted on Oct 19, 2007

Flash

Unlike last year, or last May, this morning’s GMDSS Task Force meeting seemed to yield good news about Class B AIS in the USA. The FCC has finally granted a waiver so that the various units already approved by the USCG can be sold and used even while further rulemaking takes place. The waiver needs to be reviewed by the Interdepartment Radio Advisory Committee (IRAC), but FCC representative Ghassan Khalek said that would be done in “a matter of weeks, not months”. And publication in the Federal Register will not be necessary;  the moment IRAC grants its blessing, CG and FCC approved AIS B units can be sold and used. 
   Why did I use the fudge word “seemed” in the first sentence? Well, a year ago Mr. Khalek told me that FCC Class B approval would be quick once the CG was done. So I double checked that “matter of weeks” quote with him as he exited the meeting. He nodded yes, smiled, and murmured a compliment about Panbo’s AIS coverage. Cool.

Comments

Hopefully we can start planning our spring AIS B installations!!!!!

Posted by: ibsailn at October 19, 2007 5:51 PM | Reply

So: what are our choices? Does anything come close to the ACR?

Posted by: Sandy at October 20, 2007 1:03 PM | Reply

the story i've been hearing from several sources is that Class-A users will essentially ignore Class-B signals. some Class-A hardware apparently needs a firmware upgrade to even see Class-B signals. Worse, Class-A AIS displays tend to be the IMO "minimum" text displays with precious little screen real estate which they won't waste on Class-B targets. Exacerbating the AIS situation display problem, most installed-base IMO-class radars don't display AIS targets and the most popular units (currently) cannot be upgraded to display AIS targets, even Class-A.

the net of all this is that Class-B transponders will only be seen by other Class-B units (transponders or receivers), and the awareness by big boats won't change.

there are those who argue this means that the installation choices (for those without "must-carry" requirements) come
down to either an all-class receiver-only unit, or a Class-A transponder if you care about the big boats really seeing you.
(This may be a consideration for off-shore passagemaking.)

There are two alternatives for Class-A - there are the IMO-accepted units, but there are also Class-A units designed for workboats which don't have as complete a pedigree and are somewhat cheaper. I believe ACR sells both IMO and non-IMO Class-A units. one significant differentiator between various Class-A transponders is the number and size of boxes that must be stowed and interconnected, not just the display, so make sure to compare apples to apples.

Note that i'm not asserting this is the gospel truth, but reflects a bunch of conversations i've been having around the waterfront. I hope more encouraging information appears out of the Lauderdale show and the NMEA annual meeting.


Posted by: N4NLN at October 20, 2007 8:46 PM | Reply

"some Class-A hardware apparently needs a firmware upgrade to even see Class-B signals."

I don't think so, Mike. Many Class A units DO need an upgrade to see the Class B static data message -- boat's name, dimensions, etc. -- but I believe they all see the dynamic target info, which of course includes your MMSI.

There are some truths in the the rest of your worries, but overall I think you're underestimating the general quality of gear and personnel on ship bridges.

Were you reading Panbo back in June when I tested a Class B from Bermuda to Gulf of Maine? I called almost every ship that we saw on AIS and almost all answered (a benefit you'd get with just a receiver). Of those who answered, I think every ship within 8 miles could see us on their AIS plotting device, whatever it was.

Note that commenter "ibsailing" above was on that trip with me; he saw Class B in action. It's not perfect, but it's useful. (And if you can afford a Class A transponder, go for it.)

Posted by: Ben at October 21, 2007 8:03 AM | Reply

Sandy, I think the ACR Nauticast B is excellent, but would guess that the other units are close. Most, after all, are based on the same SRT board.

But I just got to see the Simrad A150 in the flesh and think it's going to be a very popular unit, offering its own screen, N2K compatability, "buddy tracking", and data saving for not much premium.

http://tinyurl.com/2bxpay

Posted by: Ben at October 21, 2007 10:56 AM | Reply

N4NLN:
I am getting a bit concerned about this myth that seems to keep re-surfacing about Class A's not being able to see Class B's. Let me concur with Ben here and state that ALL Class A's should be able to see the msg18 sent by the Class B's. I have just dug out my copy of the Class A standard (IEC 61993) and it clearly states that a Class A MUST be capable of receiving msg18.

OK, I grant you that the Class B static data may not be seen, but that is hardly a critical failing.

I have just spent a hour on the bridge of a 30 year old cross-channel ferry (France - UK) and was pleased to see that the crew actively use their AIS units to identify risks with 4 repeater displays in operation, two of them beside the radar plots, and two in the bridge wings. It was just a shame that there wasn't a direct link between the AIS and the DSC Tx, the operator had to read the MMSI off the AIS screen and then type into the DSC manually...

Posted by: del at October 23, 2007 7:19 AM | Reply

I think these rumors started with a certain Class-A that was having trouble receiving the CSTDMA Class B transmission. I forget which it was, but they were too strict about when they expected the start of the packet to be received. This was over a year ago, so I expect it has been fixed by now.

Other than starting a little late in the slot, there is no difference between a Class-A message and a Class-B message. All AIS receivers *ought* to be able to receive any message -- they may not be capable of interpreting it, but they should be able to receive it and pass it out a serial port as a AIVDM for further processing.

In the receiver design I was involved in I made sure that any unknown message was checked for the common preamble (mmsi, mesgid) and limited to 5 slots. If it met those criteria then it was passed out the serial port to the attached device.

Posted by: bcl at October 30, 2007 8:49 PM | Reply

bcl:

del is correct on this, it's just the static data (ship name, call sign etc.) that's the problem. Class B sends these in a message that was newly defined for the Class B specification, so Class A units designed before that time don't decode them.

More recent Class A units do, and the Class B transmission of MMSI and position are always seen.

It's also the case that some chart plotters and PC charting software doesn't decode VDM's for message 24. I guess the vendors will catch up soon enough...

Posted by: marinate at October 31, 2007 1:23 PM | Reply

I just discovered the Panbo URL and what a nice source of marine electronics information. I want to thank Shine Micro for the link on their website or I probably would not have known. Keep up the blog about AIS B-Class, especially for pleasure boating as a security and safety identification. Puget Sound boaters for the most part fly safely but there are always the rogues who misoperate radios, fail to obey common sense safety and operations and make themselves a general nuisance - especially when they operate under the influence. AIS will go a long way to identify those idiots that ruin it for the rest of us safety conscious boaters. Thanks for a terrific site. KB7NES

Posted by: Rick Schurman, KB7NES at November 4, 2007 5:51 PM | Reply

Any help regarding the post I sent today to NASA (the AIS one NOT the Space one). I think NASA AIS Radar and Engine sell in the US under another brand but you probably know it.

Regards


Dear Sirs

Does your NASA AIS Radar receive signals from a COMAR CSB200 AIS B Transponder.

Last weekend I carried a test where a NASA AIS Radar didn't get the signal of a COMAR CSB200 Transponder, installed in a boat 100 meter away (the receiver got the signals of many other ships around). This proves that the receiver was operating. We waited for 30 minutes or so without getting a signal.

However the signal was picked by Lisbon Port Control some 2 miles from the transmitter. This proves that the transmitter was operating.

I assume the AIS receiver of Lisbon Port Control is not a NASA.

I ask you the question for two reasons:

1st. Here most receivers installed in sailing boats are NASA (Radar or Engine)

2nd. I read somewhere that early AIS receivers couldn´t pick AIS B transmissions.Could that be the case ?

I would appreciate if you can clarify this subject.

Regards

Posted by: Jonas at December 3, 2007 2:53 PM | Reply

Jonas, I have heard that the NASA AIS receivers have trouble with Class B signals. I think it's because, for reasons unknown, they filter out all but standard Class A messages. Unlike most every other receiver, which send along every message they receive.

I also heard that NASA can fix this problem in their receiver but you have to send it in for reflashing. I was gave NASA an Sail magazine award for their AIS receiver, but I regret it now. I've come to realize that the unit is not well made or well supported.

As for your hearing that all early AIS receivers can't see AIS B, not true! NASA is the only one I've heard of. However, many older models can not yet see the Class B static message, i.e. vessel name, size, etc. That message got changed, and so receiver/plotter software must be upgraded. But they see the Class B MMSI, position, speed, etc. fine. I know, I've tried it.

Posted by: Ben at December 3, 2007 5:16 PM | Reply

i would like to know when the simrad a150 ais is going to be availiable in the u.s. also i would like to know what the price will be in us dollars. thank you for a response...............

Posted by: tom tomas at December 16, 2007 1:04 PM | Reply

Tom, Sorry to report that I have given up predicting when the FCC will approve Class B. Here's my latest of this depressing subject:

http://www.panbo.com/archives/2007/12/ais_b_in_the_usa_depressing.html

I'm told that Simrad has A150s ready to go in a Tulsa warehouse and that they'll retail for about $1,500. I don't know if that includes GPS and AIS (VHF) antennas.

Posted by: Ben at December 16, 2007 1:28 PM | Reply

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