New Inexpensive Ais Transponder

[David M]

I have seen plenty of times pleasure boats that show up as an AIS contact long before they show up as a radar contact. That alone isn't good enough reason to get an AIS transceiver?

[Emmalina]

Originally Posted by s/v Jedi

Does your manual describe that behaviour as normal for high traffic areas? If so, you need to know that it isn't normal. I am at the Panama Canal and see 175-250 targets without a problem... on an old 1st generation black box transponder.

Its onla a Nasa Marine thing with a 2.5 inch screen and the manual is about 150 words ...
More than 30 boats and its not readable in radar mode but hey Cheap and cheerful..

[az_r2d1]

I think the more boats have ais transponders the better.

You can definitely NOT rely on radar reflectors commonly installed on pleasure boats to be seen on radar. Most do NOT work well enough to be seen.
I've seen tests done by a Dutch sailing magazine and the cheaper reflectors were useless. Only 1 or 2 models were actually worth buying. The rest was garbage.

[vRUN]

Originally Posted by az_r2d1

I think the more boats have ais transponders the better.

You can definitely NOT rely on radar reflectors commonly installed on pleasure boats to be seen on radar...

+1
You may want to have a look at :
http://www.theradarreflectorsite.org

...active radar reflectors do work!

[Powerabout]

the golden rule on a commercial vessel is if you cant see it on the radar it wont do any damage when you run it over.
Class B filtered out, dont worry about that, what about the millions of ships out there with crt radars, for them the AIS is a box in the corner, never looked at as AIS is NOT a collision avoidance tool for commercial shipping.

It has become a very useful tool for yachts to see large vessel and avoid them...
And radar reflectors dont work either...
I have been on both ends of that checking it for myself as a yachty and commercial crew.

[MarkJ]

Originally Posted by Powerabout

Class B filtered out, dont worry about that, what about the millions of ships out there with crt radars, for them the AIS is a box in the corner, never looked at as AIS is NOT a collision avoidance tool for commercial shipping.

The only commercial captain in the world who would see any truth in any of your statements is the Captain of the Costa Concordia.



Mark

[jeremiason]

Originally Posted by Powerabout

the golden rule on a commercial vessel is if you cant see it on the radar it wont do any damage when you run it over.
Class B filtered out, dont worry about that, what about the millions of ships out there with crt radars, for them the AIS is a box in the corner, never looked at as AIS is NOT a collision avoidance tool for commercial shipping.

I am not sure who you were working for, but at least in San Francisco Bay when I was working commercially, we used AIS as one of the tools for collision avoidance.

People keep pointing to the Filtering Device on AIS Class A that filters out Class B AIS. The truth is the Class A AIS has several filtering devices, which filter out targets by distances and action. An example is you can filter out Anchored vessels or vessels more than a certain distance form your ship. Yes they can filter Class B AIS as well...

The real truth is not many Captains or Watch Officers want to risk their licenses on collision with a recreational vessel, especially one equipped with Class B AIS since AIS transmissions recorded for posterity and the subsequent civil and criminals trials.

USCG Rule 5 - Lookout
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

This rule has been interpreted by the USCG to mean ALL ELECTRONIC DEVICES as well as visual... Including VHF, Radar and AIS. They have also held that if the device is installed it better be on, which is one of the reasons you see commercial vessels with their radar on during the day in clear conditions.

Not many people realize this also applies to recreational boats, meaning that if you end up in a collision and have a radar or other anti-collision devices on your recreational boat and you were not using them or they were turned off, you can be held both criminally and civilly responsible under Rule 5.

[St. Elsewhere]

Originally Posted by jeremiason

USCG Rule 5 - Lookout
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

This rule has been interpreted by the USCG to mean ALL ELECTRONIC DEVICES as well as visual... Including VHF, Radar and AIS. They have also held that if the device is installed it better be on, which is one of the reasons you see commercial vessels with their radar on during the day in clear conditions.

Not many people realize this also applies to recreational boats, meaning that if you end up in a collision and have a radar or other anti-collision devices on your recreational boat and you were not using them or they were turned off, you can be held both criminally and civilly responsible under Rule 5.

Best advice I've seen here . . .

[ka4wja]

Powerabout,
1) Since you joined Cruiser's Forum over a year ago, I assume you're not trolling here, and are actually serious???
So, I was just wondering what backwater maritime academy did you attend, and/or what loser captains have you crewed under???
'Cause this is a load of BS!!

Originally Posted by Powerabout

the golden rule on a commercial vessel is if you cant see it on the radar it wont do any damage when you run it over.
Class B filtered out, dont worry about that, what about the millions of ships out there with crt radars, for them the AIS is a box in the corner, never looked at as AIS is NOT a collision avoidance tool for commercial shipping.

I'm usually not one to jump on another's right to express their opinions, so please excuse me here....
This is a load of CRAP!!!






2) And, I don't wish to quibble, but my understanding of this "filtering issue" / myth, is a bit different..

Originally Posted by Powerabout

Class B filtered out, dont worry about that

Originally Posted by jeremiason

The truth is the Class A AIS has several filtering devices, which filter out targets by distances and action. An example is you can filter out Anchored vessels or vessels more than a certain distance form your ship. Yes they can filter Class B AIS as well...

My understanding is that any vessel transmitting AIS (whether Class A or Class B), that produces a CPA and/or TCPA, which is within whatever the "Minimum CPA" and/or "Minimum TCPA" settings the other vessel's AIS Transponder has (either the defaults or those set by the vessel's master):
a) will trigger an alarm/alert in the AIS Transponder of the other vessel (the "thing" with the MKD, "Minimum Keyboard and Display"), NO MATTER WHAT FILTERING may be selected on the vessel's ECDIS (Electronic Chart Display and Information System)....and that all AIS target information is always received and available in the AIS Transponder's MKD (although not likely viewed often)...
b) as well as show this "dangerous" target on whatever ECDIS is connected to the AIS Transponder...

My understanding (based on my reading of the IMO specs on AIS, as well as reading the Panbo site years ago, when this "Class B filtering myth" started) is that, in effect this means that while commercial vessels (w/ Class A AIS and ECDIS) CAN filter out many vessels from their ECDIS (including many Class B vessels), BUT...
But, they are NOT filtered from the AIS Transponder (and target info is still available there on the AIS Transponder's MKD), and will still alert/alrm should these filtered targets be "dangerous" targets (falling inside the minimum CPA / TCPA settings)....
And, further, even if they would be "filtered" by the vessel's ECDIS settings, they WILL show up on the vessel's ECDIS display and be shown on the ECDIS as a "dangerous" target, once they fall inside the minimum CPA / TCPA limits....

Again, I don't wish to quibble, nor complicate matters for anyone here...but, I see much discussion about "filtering" as though it somehow makes Class B AIS systems less useful (or even worse, a "waste of money")....and the truth appears to be the opposite!!!
While NO electronic aide is a replacement for a "look-out" / "watch-stander", AIS does work quite well as an AIDE to collision avoidance...





3) And, everyone should read Tom's posting again...

Originally Posted by jeremiason

USCG Rule 5 - Lookout
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

This rule has been interpreted by the USCG to mean ALL ELECTRONIC DEVICES as well as visual... Including VHF, Radar and AIS. They have also held that if the device is installed it better be on, which is one of the reasons you see commercial vessels with their radar on during the day in clear conditions.

Not many people realize this also applies to recreational boats, meaning that if you end up in a collision and have a radar or other anti-collision devices on your recreational boat and you were not using them or they were turned off, you can be held both criminally and civilly responsible under Rule 5.

4) Finally, regarding radar reflectors....

Originally Posted by Powerabout

And radar reflectors dont work either...
I have been on both ends of that checking it for myself as a yachty and commercial crew.

Actually they DO work....but they just don't do what some think they do!!!
I don't have the time to go into details, and I cannot fathom anyone who ever passed a commercial mariners exam not knowing this???

But, for those interested, you may find the in-depth studies of radar reflector effectiveness and actual RCS (radar cross section) area needed to actually provide reliable target echos, to be very informative....
Bottom line, the Davis Echomaster reflector in the "catch-rain-mounting-configuration" is pretty good...with the BIGGER, HEAVIER and more expensive "LARGE tri-lens" reflectors showing marginally better....and "electronic" radar target enhancers to be the best....and NOTHING other than these 3 options being worth bothering with....
(most sailors will find a Davis reflector, in the catch-rain-configuration, mounted as high as possible, to be a fairly effective reflector..or even better, TWO of them set 45* apart azimuthally....)

If anyone is curious, please read the many reports/studies on these matters...
Such as the UK's MAIB report...
http://www.maib.gov.uk/cms_resources...s%20report.pdf





Okay, enough of my rambling today...


Fair winds to all..

John
s/v Annie Laurie

[bfloyd4445]

Originally Posted by onestepcsy37

i came across this ais transponder today. it's advertised as the lowest cost transponder and also self contained with it's own battery and antenna. couldn't find a price for it.

AIS Identifier

sounds like it's just what i want. i only need an ais to cross the gulf stream at night - florida to bahamas. i just want to be visible to other ships, don't really need or want to track them. so i'm looking for something that's self contained and inexpensive. this one seems to fit.

i know dirt about ais so i'm asking the electronics experts out there to tell me what they think of it, given my requirements. my concern is that it seems to work only on certain 'channels' and i don't know if these are the 'channels' that regular ais works on, so will i be visible to ships if i use this device?

all ais people please advise....

I think what that is is a unit like this one at west marine and will work for what you want https://www.westmarine.com/webapp/wc...MobileOptOut=1

[Paul Elliott]

Originally Posted by bfloyd4445

I think what that is is a unit like this one at west marine and will work for what you want https://www.westmarine.com/webapp/wc...MobileOptOut=1

This Garmin unit is a receiver, not a transponder. It does not transmit an AIS signal. Garmin does make an AIS transponder but it costs about $900 -- not the cheapest.

[bfloyd4445]

Originally Posted by Paul Elliott

This Garmin unit is a receiver, not a transponder. It does not transmit an AIS signal. Garmin does make an AIS transponder but it costs about $900 -- not the cheapest.

I understand that but the original question was regarding a unit that was neither a nor b and units sold like that are often like the garmin I mentioned. They will warn you of any ais equipped vessels in your area and that is what I would like especially in the fog.

[Paul Elliott]

Originally Posted by bfloyd4445

I understand that but the original question was regarding a unit that was neither a nor b and units sold like that are often like the garmin I mentioned. They will warn you of any ais equipped vessels in your area and that is what I would like especially in the fog.

OK, but the Original Poster wanted "to be visible to other ships" (via AIS). This of course requires a transponder of some sort. Actually, I think the OP wanted a transmit-only AIS beacon (a bad idea in my opinion). I do think that a receive-only unit can be hugely useful though.

[bfloyd4445]

Originally Posted by Paul Elliott

OK, but the Original Poster wanted "to be visible to other ships" (via AIS). This of course requires a transponder of some sort. Actually, I think the OP wanted a transmit-only AIS beacon (a bad idea in my opinion). I do think that a receive-only unit can be hugely useful though.

Ah, then I got it backwards. I thought he wanted to see other ships. He then will need A or B

[rebel heart]

Originally Posted by jeremiason

You are correct that AIS Class A will transmit 30-60 miles, DEPENDING on the height of both the transmitting and receiving antennas, but Class B will only transmit about 8-12 miles, again depending on the height of the Antennas...

I was pretty surprised that I saw AIS contacts from > 95 miles away the other day. I was in Puerto Escondido and saw three ships (class A) in San Carlos pop up. My masthead is ~55' off the ground, and they're probably ~80' off the ground, but still, I was surprised to say the least.