PLB Personal Locator Beacon Explained

[Dockhead]

Originally Posted by Kenomac

Does the Ocean Signal MOB1 have a test function, so practice MOB situations can be rehearsed using the system?

Yes!


You can even set it off, not in test mode. The battery is good for many hours of transmission. Unlike a PLB, say, setting it off for real, doesn't require it to then be sent back for a battery replacement.



I'm really impressed with this device, which is incredibly tiny -- a fraction of the volume of my first generation, early adopter McMurdo AIS MOB beacon.


Also quite reasonable price, I thought -- I only paid £200. At that price, and with 7 year battery life, I should probably refit all of the life jackets on board with those.

[Kenomac]

How many did you have onboard on your way to Greenland last year? I'm thinking two Ocean Signal MOB1 units will be plenty on our boat to handle just the two of us or for two people on watch when we have crew for overnight passages.

In calm conditions, we reside within the center cockpit on both boats which is quite safe, but when going forward in any thing above 15-17 knots, we always wear a life jacket. When the wind increases above 20 knots, we also wear them in the cockpit.

[Kenomac]

Dockhead,

How do you attach your ACR ResQLink onto your lifejacket?

[Singularity]

Originally Posted by Dockhead

PLB's don't transmit anything by DSC. They emit a 440mhz signal to COSPAS-SARTSAT satellites, which go through the SAR services to activate a search and rescue action after the protocols are followed, which takes some hours. They also emit a 121.5mhz homing signal to guide the rescue helicopter or cutter the last mile to your position.


AIS MOB beacons are an entirely different animal. They emit a VHF signal on Channel 70 showing the location of the beacon on local AIS sets, and some of them, the latest ones, will also send out a DSC distress message -- again, to local vessels.


Got it? In a nutshell:


PLB -- via satellite to SAR services after some hours


AIS beacon -- via AIS, and sometimes via VHF DSC distress messages, to LOCAL vessels

One is satellite to SAR -- no local vessels. The other is AIS and sometimes DSC to local vessels only -- no SAR.

So I understand the satellite to SAR part. Frankly I don't think of 121/406 stuff with respect to saving someone in the water (if you know what I mean).

My confusion remains, which I think is the original question...is about what occurs locally around the activated MOB device. My assumption was that the MOB PLB (in particularly the referenced MOB1 PLB) will, effectively:
1) scream a signal on VHF channels 16 and 70 up to ~5 miles

2) show up on all local AIS receivers within ~5 miles

So what we want to know is if an activated MOB1 device will show up on all the listening AIS receivers in the area (+/- range issues). Apparently not all AIS receivers will process the direct call of the PLB, even if in range???

[Dockhead]

Originally Posted by Kenomac

Dockhead,

How do you attach your ACR ResQLink onto your lifejacket?

The large 275N Seago ones, which I've had for 10 years -- they go into a pocket, with a lanyard to prevent the PLB from getting washed out of my hand.


The new Spinlock, this:





Which attaches to the standard studs on the life jacket, left side.


There is a mesh pocket on the right side of the Spinlock jacket, for "PLB or VHF", but it's too small for the ResQLink.

[Kenomac]

Originally Posted by Singularity

So I understand the satellite to SAR part. Frankly I don't think of 121/406 stuff with respect to saving someone in the water (if you know what I mean).

My confusion remains, which I think is the original question...is about what occurs locally around the activated MOB device. My assumption was that the MOB PLB (in particularly the referenced MOB1 PLB) will, effectively:
1) scream a signal on VHF channels 16 and 70 up to ~5 miles

2) show up on all local AIS receivers within ~5 miles

So what we want to know is if an activated MOB1 device will show up on all the listening AIS receivers in the area (+/- range issues). Apparently not all AIS receivers will process the direct call of the PLB, even if in range???

Yes! I have the same confusion on the subject.

I want to provide safety aboard, but I also want to spent the money wisely on a system we can practice using.

[Dockhead]

Originally Posted by Singularity

. . .My confusion remains, which I think is the original question...is about what occurs locally around the activated MOB device. My assumption was that the MOB PLB (in particularly the referenced MOB1 PLB) will, effectively:
1) scream a signal on VHF channels 16 and 70 up to ~5 miles

2) show up on all local AIS receivers within ~5 miles

So what we want to know is if an activated MOB1 device will show up on all the listening AIS receivers in the area (+/- range issues). Apparently not all AIS receivers will process the direct call of the PLB, even if in range???

Yes, this is right -- just, no Channel 16. Only digital DSC messages (repeated every 30 seconds) on Channel 70 only. But DSC equipped VHF sets (all made since 15 or so years ago) will sound a loud alarm.



I can't answer the question about WHICH devices it works on. I would think all of them. In any case, my own pretty old AIS transceiver certainly picks up AIS MOB signals, and these are shown as MOB! on my pretty old Zeus chart plotters.

[Dockhead]

Originally Posted by Kenomac

Yes! I have the same confusion on the subject.

I want to provide safety aboard, but I also want to spent the money wisely on a system we can practice using.

It might be worthwhile to buy THREE of them -- one each for you and your wife, and one purely for practice (could be used later in case you have a guest). Since these don't talk to SAR, you can just set them off. You could just jump overboard and let the life jacket inflate automatically, and see if it sets off the beacon as designed.



Have someone standing by in the RIB as a safety boat, and put out a Securite message on VHF, warning that you are testing a MOB beacon, and that the signals are not a real MOB.


I am a great believer in live practice. I think you have a very good idea there.


I also believe that these devices are total game-changers for MOB situations, almost eliminating what was the scariest segment of MOB rescue -- finding the victim.



I've had MOB beacons on board for 15 years, so I guess you could say I'm an early adopter. I used to have an old an hyperexpensive system designed for oil platform workers, which consisted of 121.5mhz homing beacons you wore around your neck, and a directional receiver. Then the first AIS beacons appeared, and I bought the first one sold in the UK, this one:





The exact size and shape of a vibrator. I keep it hidden so that visitors don't get the idea that I keep sex toys on board. At the time I thought it was the dog's danglies, but it is light years behind the latest ones. It is totally manual, and requires you to pull a pin, and then twist the handle, then hold it up. Good luck with all of that in a storm, in cold water! The MOB1 is vastly better.

[Kenomac]

If we were to practice a MOB using the Ocean Signal MOB1 device, would a signal go out to all vessels, or can it be more localized? I wouldn't want to alert the masses by accident.

The plan will be to test everything in real life around May 20 when we leave Italy. I'm thinking it might be a good idea to chuck a life ring overboard with something bright green along with the locator beacon, then after we find it, make the human wearing a drysuit substitution. Of course the dinghy will be in attendance.

We're good at rescuing life rings, but I want to add humans to the mix if, and only if it can be done safely.

[Paul L]

Originally Posted by Kenomac

If were were to practice a MOB using the Ocean Signal MOB1 device, would a signal go out to all vessels, or can it be more localized? I wouldn't want to alert the masses by accident.

Check the Ocean Rescu mob1 manual for the test directions. They detail how to set off a DSC test and an AIS test. They also list how many times you can do the test before running down the battery.
Manual is downloadable.

[Kenomac]

Originally Posted by Paul L

Check the Ocean Rescu mob1 manual for the test directions. They detail how to set off a DSC test and an AIS test. They also list how many times you can do the test before running down the battery.
Manual is downloadable.

Thanks, I'm also looking for a product video online.

[Dockhead]

Originally Posted by Paul L

Check the Ocean Rescu mob1 manual for the test directions. They detail how to set off a DSC test and an AIS test. They also list how many times you can do the test before running down the battery.
Manual is downloadable.

Yes, that's right. You can set it off in test mode, so that it only sends a DSC to your MMSI, not an all ships. But the AIS transmission goes to everyone. But this is not a big deal if you put out the Securite call first to warn that you are testing.

[Paul L]

Originally Posted by Kenomac

This time, I’m looking to find what will work best in our situations, where we sail primarily in the warm waters of the Mediterranean and Caribbean with SAR not far away. ......

Not sure where in the Carib you are planning, but you won't get first world SAR in much of the eastern or western Carib. Far better to rely on DSC/AIS self rescue for any MOB situation. Long distance, slow vessel rescue is where the EPRIB will come into play.

[Kenomac]

Originally Posted by Paul L

Not sure where in the Carib you are planning, but you won't get first world SAR in much of the eastern or western Carib. Far better to rely on DSC/AIS self rescue for any MOB situation. Long distance, slow vessel rescue is where the EPRIB will come into play.

Understood. Do you know if an extra battery for the MOB1 is available and can be easily changed by the user? Is it possible to have a "practice battery," so the full charge in the beacons can be maintained?

[Dockhead]

Originally Posted by Paul L

Not sure where in the Carib you are planning, but you won't get first world SAR in much of the eastern or western Carib. Far better to rely on DSC/AIS self rescue for any MOB situation. Long distance, slow vessel rescue is where the EPRIB will come into play.

That's right. Very spotty SAR coverage in the Carib. But even with first world SAR service -- note carefully that due to the procedure, it takes at least several hours, to get a response.