Aerials for AIS

geem said:
It's not just seeing, it's being seen. Class B is only 2W transmission power. A good antenna is beneficial. We often only see other yachts at 2 or 3 miles. Friends reported we were visible at 13nm. When crossing Biscay shipping lanes, its nice to know that huge ships see us in good time. They don't alter course so easily
Click to expand...
Oddly, I've watched friends sail from St Malo, France to Falmouth, Cornwall all on AIS they were delighted with the screenshot I sent them from Marine Traffic as they were concerned that their AIS was not working.

By some strange atmospherics I've spotted friends 50 NM north west of Ouessant, Ushant for the hard of hearing, returning from Cuba and was able to call friends and get the party planning started. I will admit it was a fluke as their signal was only visible for 15 minutes.

When crossing the Thames Estuary in 2021 One Manhattan 153,453 gross tonnes very politely changed her course by 2° for a mile, as I was the stand on vessel. I have no idea if she looked at AIS or radar to see me. I understand that ships primary use radar rather than AIS.
 
Pye_End said:
Incorrect interpretation.

Ships will almost always give way if that is their duty, particularly when offshore. It's the ones that seemingly aren't keeping watch that you need to take a bit more care over!

I don't know how many miles they like to make course adjustments, but without a transponder on a yacht they almost all seem to do the right thing in good time. 8 miles with the antenna on the guardrail is plenty. Guard zone of 4 miles is more than adequate offshore.
Click to expand...

I take pride in being one of MANY who stood watch on bridge of ship and altered course regardless of size of other vessel according to Colregs.
 
Sandy said:
Oddly, I've watched friends sail from St Malo, France to Falmouth, Cornwall all on AIS they were delighted with the screenshot I sent them from Marine Traffic as they were concerned that their AIS was not working.

By some strange atmospherics I've spotted friends 50 NM north west of Ouessant, Ushant for the hard of hearing, returning from Cuba and was able to call friends and get the party planning started. I will admit it was a fluke as their signal was only visible for 15 minutes.

When crossing the Thames Estuary in 2021 One Manhattan 153,453 gross tonnes very politely changed her course by 2° for a mile, as I was the stand on vessel. I have no idea if she looked at AIS or radar to see me. I understand that ships primary use radar rather than AIS.
Click to expand...

It may surprise but the target of AIS is shown on CAS Radar ... but in terms of data - the operator usually has to highlight the target to see the data. it has to be appreciated that the receiving antenna for AIS on a ship is usually far higher than that of a yacht. This means that ship is receiving more targets.

YES - ships would use radar primarily - but that does not over-ride fact that one or more of the display systems on the bridge will have AIS input. How the alarms are set - depends on Masters overall decision ....
 
Pye_End said:
Incorrect interpretation.

Ships will almost always give way if that is their duty
Click to expand...

''Almost'' isn't good enough
The first duty is to avoid the possibility of a collision situation in the first place . And that is most easily achieved buy the most manoeuvrable vessel.
 
MartynG said:
''Almost'' isn't good enough
The first duty is to avoid the possibility of a collision situation in the first place . And that is most easily achieved buy the most manoeuvrable vessel.
Click to expand...
How you behave before a situation develops is up to you. However COLREGS do NOT comment in any way that 'small must give way to big'.

'Almost' is important - COLREGS say that you must not carry on regardless if the give way vessel fails to take sufficient action.

The most important thing about avoiding collisions is being predictable, hence a set of rules that set out to make this easier.
 
geem said:
Don't what happened there! My post didn't appear.
Anyway, I was going got say that out in the Ocean, ships seem to have their RADAR/AIS set to give a 1nm offing. This happens 99% of the time.
Click to expand...

A 1nm passing is common as it doesn't affect other vessel. As an ex OOW ... I would 'plot' to have at least 1nm passing with another vessel whenever possible.

As a Master said to me when I was Cadet .... Why do you want my bit of water when there's a whole bloody ocean out there ???

In Maritime College - lecturer said : A collision occurs when two idiots decide to be in same water at same time.


QED !!
 
MartynG said:
''Almost'' isn't good enough
The first duty is to avoid the possibility of a collision situation in the first place . And that is most easily achieved buy the most manoeuvrable vessel.
Click to expand...

Marvelous .... we shall now ignore Colregs ....

BUT .....

When I was in Aural examination for one of my Certificates .. examiner asked me about my actions when meeting a Tug and Tow.

My answer was that although Colregs may dictate action - as I was the more manoeuvrable vessel - I would make sound signal and BOLD alteration of course to allow him to pass ...
My claim being Prudence rather than standing on.

Examiner applauded my answer.

That does not excuse your post MartynG ...

Are you aware that collisions can occur because one of the vessels does NOT follow ColRegs ?? That "most manoeuvrable vessel." by not following the rules could in fact create the very situation that leads to disaster ??

Anyway ... not really Antenna matter
 
Refueler said:
It may surprise but the target of AIS is shown on CAS Radar ... but in terms of data - the operator usually has to highlight the target to see the data. it has to be appreciated that the receiving antenna for AIS on a ship is usually far higher than that of a yacht. This means that ship is receiving more targets.

YES - ships would use radar primarily - but that does not over-ride fact that one or more of the display systems on the bridge will have AIS input. How the alarms are set - depends on Masters overall decision ....
Click to expand...
Thanks for the update it has been some time since I was last on the bridge of either a merchant or warship. In both cases they kept me well away from any buttons. ;)

EDIT: Come to think of it I was on the bridge of RFA Argus in August 2022, but she was tied alongside.
 
Sandy said:
Thanks for the update it has been some time since I was last on the bridge of either a merchant or warship. In both cases they kept me well away from any buttons. ;)

EDIT: Come to think of it I was on the bridge of RFA Argus in August 2022, but she was tied alongside.
Click to expand...
Lovely ship. Taxpayer got moneys worth with that one! Did three trips in her including her first big refit in Middlesbrough.
 
MartynG said:
''Almost'' isn't good enough
The first duty is to avoid the possibility of a collision situation in the first place . And that is most easily achieved buy the most manoeuvrable vessel.
Click to expand...
The best way to avoid the possibility of a collision situation is to stick to the regulations that way everyone knows what to do. Manoeuvrability is well covered by the regulated vessel categories and most definitely not by guesswork.
 
MartynG said:
Would you expect a ship to alter course for you if some miles off the shore?
Click to expand...
After fitting our AIS transmitter we found that they very often did and whilst ships regularly showed up on the AIS screen if we saw them at all it tended to be on the far horizon.
Our assumption was that they considered it easier to tweak course early and by just a few degrees thus ensuring they kept well clear of the WAFI.
 
Buck Turgidson said:
The best way to avoid the possibility of a collision situation is to stick to the regulations...
Click to expand...
The 'regulations' of which you speak only come into effect once a risk of collision exists, so the best way to avoid a collision is to manoeuvre early and prevent that risk from arising. That's the beauty of AIS, because you become aware of each other far earlier you have ample time to monitor each other's course and speed for a while prior to making any decision on what relatively slight alteration, if any, is needed to pass well clear of each other.
 
Alex_Blackwood said:
Lovely ship. Taxpayer got moneys worth with that one! Did three trips in her including her first big refit in Middlesbrough.
Click to expand...

A cracking ship. I take my hat off the medical staff who work on her. Conditions looked 'cramp'.

My late father served on RFAs back in the 1950s and on his first trip came into Falmouth so the visit was rather poignant.
 
oldgit said:
Bog standard fibreglass budget VHF aerial works very well providing an AIS signal for my Raymarine Nav system.
Click to expand...
Same here, it has to, as my AIS is integral to the VHF.

The vast majority of leisure AIS are either using a splitter, or the AIS has an inbuilt splitter, so clearly no issues with using a VHF antenna.
 
PaulRainbow said:
Same here, it has to, as my AIS is integral to the VHF.

The vast majority of leisure AIS are either using a splitter, or the AIS has an inbuilt splitter, so clearly no issues with using a VHF antenna.
Click to expand...
Not only that, but a good many are on motor or powerboats with much less height. Mine is at the masthead via a splitter and works perfectly well, but it seems that even a suboptimal set-up can be 'good enough' for practical purposes, even if it makes sense to achieve the best practicable.
 
You must log in or register to reply here.

Other threads that may be of interest

Y
VHF aerial pushpit mounted
Replies
15
Views
483
RunAgroundHard
RunAgroundHard

Share this page

Top