Personal AIS beacon for SAR

[martini]

http://www.worldfishing.net/features...nd-s5-ais-sart

Been around for a year but new to me

[Channel Ribs]

Originally Posted by martini

Been around for a year but new to me

They have not started marketing it in earnest yet and when they do it will be at the commercial sector. Expect to pay around 360 quid.

This shows that commercial shipping are starting to adopt inbound AIS data, the days of targets being shown in list form on a monochrome screen in the corner are behind us. Any new equipment fitted to a commercial vessel must allow for AIS data display.

[BogMonster]

I think it's a brilliant system - got a basic AIS display on my plotter - but it's not foolproof. A lot of ships seem a bit intermittent in how often they broadcast an AIS update, some are every few seconds, others can be five minutes apart, ok if they are at anchor but less ok if they are moving fast! The other thing that annoys me is an AIS alarm which goes off when you get close to anything which on a rib is a PITA, I expect it's a Garmin specific issue with the 556 but you don't appear to be able to switch it off.

Interesting looking bit of kit that.

[Channel Ribs]

Originally Posted by BogMonster

The other thing that annoys me is an AIS alarm which goes off when you get close to anything which on a rib is a PITA

I think you can turn it off, but you can also change the "range" and the "time to" in the configure menu. If you set them both to minimums you might get more peace and quiet.

Configure, other vessels, AIS alarm

Range: 500 ft. to 2.0 nm

Time to: 1 to 24 minutes

AIS Alarm: on or off

[BogMonster]

Sadly you have to go through that process every time you turn the plotter on and even with the alarm "off" it still comes up red on the display when you get close to anything which when you're whizzing through a harbour full of jiggers anchored a couple of hundred metres apart causes a fair amount of red on the display

I did think the other day that it was just as well I didn't have a full AIS transponder or it would cause mass panic in the local shipping when they glance at their plotter and see a target 300m away and closing at 40 knots

Back on topic I wonder what the range is of that transponder as the little AIS aerial on my boat doesn't have great range, only line of sight up to about 4-5 miles I guess, and that's on then A frame, one at water level would be much less? I haven't figured out why as a handheld VHF has better range than the AIS signals and the aerial is about the same size.

[Channel Ribs]

Originally Posted by BogMonster

Sadly you have to go through that process every time you turn the plotter

I was sure the plotter remembers the config settings.

Originally Posted by BogMonster

the little AIS aerial on my boat doesn't have great range, only line of sight up to about 4-5 miles I guess

Based on other installations I would expect a rubber ducky at 1m above sea level to pick up commercial AIS signals from as far away as 20nm. By commercial I mean the transmitting vessel has a good sized antenna and it is mounted many meters above sea level.

Likewise even at sea level the distress transmitter ought to be able to reach a fair range when the receivers are helicopters, tankers and lifeboats. As a way of broadcasting your position it is perhaps more akin to an electronic flare?

[BogMonster]

Don't know if it is supposed to but mine doesn't anyway, at least not for that.

I have the ANT200 receiver but I still think it ought to work better than it does but it is OK for what I need.

[chris123]

Originally Posted by BogMonster

I think it's a brilliant system - got a basic AIS display on my plotter - but it's not foolproof. A lot of ships seem a bit intermittent in how often they broadcast an AIS update, some are every few seconds, others can be five minutes apart, ok if they are at anchor but less ok if they are moving fast!

There are a few possible issues:

1. The AIS transmit rate will automatically vary itself based on the speed of the transmitting vessel - for a class A from something like once every 2 seconds at high speed to once every 3 minutes when anchored.

2. Class A AIS takes priority over class B - if there is a lot of class A traffic, you can get into the situation where the class B struggles to get a timeslot and therefore its update rate drops.

3. A lot of AIS receivers have a single receiver switching between AIS frequencies (like a VHF in dual watch). Consequently they can miss some of the messages.

4. Output power for a class B is only 2 watts (class A is 12.5 watts)

Cheers

Chris

[BogMonster]

What governs whether somebody uses A or B?

I don't think traffic congestion is an issue here

[willk]

Stephen, perhaps could your plotter be set to exclude AIS targets outside a certain range - I know this is an option on some units?

[chris123]

Originally Posted by BogMonster

What governs whether somebody uses A or B?

I don't think traffic congestion is an issue here

I didn't think congestion would be an issue for you, thought I had better cover all the bases just in case .

Class A is an IMO / SOLAS requirement for big ships (300 tons+?) and all (international?) passenger ships. If you are not mandated to have class A, I think it is just personal choice - however class A is a lot more expensive than class B, and has extra requirements - for example class A has to have its own VHF aerial, class B can use an aerial splitter to share a VHF radio aerial.

For an open boat, I am not aware of any waterproof class A transceivers - there are a few options for waterproof class B.

Cheers

Chris