EPIRB, PLB, Tracker. What's the difference?

[grantmc 59]

Hoping some of you smart people might know whether money would be better spent, (and safety improved) with a tracker beacon like a De Lorme or Spot on the boat, rather than say an EPIRB. 

 

It strikes me that the tracker beacons do much the same thing and one can also include a message.

 

And would someone please explain what the difference is between an EPIRB and a PLB anyway? Does any difference matter or are the acronyms effectively just synonyms caused by branding?

 

Are all EPIRBs made equal, or are there unique product features and benefits?

[Brendon 0]

The basic difference between a PLB and an EPIRB, is an EPIRB is designed for marine use and will float with it's aerial above the water and transmit a signal for a long period. A PLB wont float, it is designed to be compact so you can carry it with you.

 

So if your boat goes down and you are in the water how long do you think you will be able to hold your PLB above the waves?

[Island Time 1,239]

Plus proper epirbs and PLBs transimitt on frequencies that the rescue services monitor directly. Tracking systems don't and rely on the service provider to pass on distress messaged to the relevant authorities. For me, you want rescue, no substitue for a proper epirb on a boat or raft.

[rigger 47]

One other to consider if you are in an area with lots of vessels with AIS is an AIS SART.

[Island Time 1,239]

True, but only if the boat is ALWAYS in coverage area, Otherwise EPIRB for the Boat, and AIS SARTS for the people - + at least a AIS receiver on the boat so you can find your own crew if they go over the side...

[too_tall 15]

From personal experience, the tracker/messenger units can be fickle in the delivery timing of messages - sometimes many hours pass between sending and receiving. Great for getting messages to people, maybe in getting instructions for assistance, but not at all a substitute for an EPIRB or PLB.  

[erice 732]

think also so that an epirb needs to be able to broadcast for 48hrs (because you drift on water?)

 

than a plb 24hrs (because you don't on land)

 

Personal Location Beacons work in exactly the same way as EPIRBs by sending a coded message on the 406 MHz distress frequency which is relayed via the Cospas-Sarsat global satellite system.

 

However, there are a number of differences between them. PLBs are designed to be carried on the person so they are much smaller, some such as the Fast find are not much larger than the size of a mobile phone. PLBs are designed to be used anywhere in the world, on the sea and also on land. Some don't float but may come with an additional floatational sleeve which they should be carried in.

 

PLBs, once activated, will transmit for a minimum of 24 hours; while the battery life on an EPIRB is at least double (a minimum of 48 hours).

 

An EPIRB is registered to a vessel, whereas a PLB is registered to a person. This means that if you are crewing a yacht and you switch to a new yacht the plb is still correctly registered; however, if you have an EPIRB and buy a new yacht you will need to re-register it when installing in your new boat.

 

http://www.epirb.com/difference_between_EPIRBs_PLBs.php

[erice 732]

An injured English climber trapped in a tight steep gully in the Aoraki Mt Cook National Park alerted the United Kingdom Coastguard to get help.

 

The 64-year-old Leeds man, who was climbing solo on the western slopes of Mt Mabel, 7km south of Mt Cook, activated his UK-registered personal locator beacon after slipping on snow and injuring his leg on rocks about 8pm on Sunday.

 

http://www.stuff.co.nz/timaru-herald/news/75768117/injured-british-man-winched-from-mt-cook-national-park-with-help-from-uk-coastguard

[grantmc 59]

So they do work. Wow!

[Black Panther 1,592]

What exactly can AIS do for a man overboard? (This is a real question)

[Beccara 25]

It broadcast's faster but has a limited range. If someone falls over on a boat and the plotter is setup right it will trigger an alarm and show the location from the AIS beacon on the person in the water. This updates more and is available directly to local ships whereas a PLB/EPIRB device sends updates less frequently and is only accessible to SAR centers and must be relayed to ships in the area through a different means.

 

EPIRB activation's require 2 passes for a track to be established and SAR units to be sent. Once this is done and assets are closer to the area either EPIRB's with 121.5mhz localizers or AIS devices will allow the assest to home in on the person. 121.5mhz requires special kit so this is only useful for SAR unit's however if the asset moved to assist in the operation is something like a fishing vessel then AIS will allow the vessel to locate the person in real time without additional support from SAR centers relaying space based EPIRB gps locations.

 

Hopefully that makes some sense lol, It's tricky because some people view all these devices as one group serving one function when in reality it's multiple tools for multiple jobs

[Beccara 25]

There are more things to consider than just the claimed accuracy of the gps chip set and the update time of the unit.

 

First off, GPS does have bad days - Over the following month in Whangarei NZ the GPS accuracy will shift around quite a few meters and sats in view used for a lock will change from 3 to 5. Whilst more may be in view at the fringe they will detract from accuracy so the chip will reject their use.

 

Next up, The COSPAS-SATSAR spec shows that without Doppler from LEO all positions from from the EPIRB/PLB will still be treated as position not confirmed. Once a doppler fix can be done which requires 2 tracks from LEO birds the an updated incident message will be sent but only if the doppler fix and encoded position from the EPIRB/PLB match

 

This is all outlined in the COSPAS-SATSR system document A001.

 

If this a a MOB event and the person is shifting then the encoded GPS location from the beacon will not match the doppler tracked position often so your incident will be sent out as position not confirmed or worse you will go from position confirmed to position conflicted. This means that SAR teams will treat the incident differently and may not just go straight to you and/or may just operate from a general search grid around the area.

 

EPIRB/PLB alerts people your in danger and gives you a rough area to send people to, 121.5mhz beacons and AIS get help in your area to you as quickly as possible. Whilst SAR teams are trained for and do work where people have no GPS EPIRB's or have an alarm raised via other means you drastically increase your survival chances by have both a GPS EPIRB with 121.5mhz beacon AND an AIS SART

[Black Panther 1,592]

Ok, so in among all the techno speak. If you have AIS, and if the crew is wearing something, that something will tell you if the crew fell overboard and where the crew is relative to the boat. Sounds a huge improvement on a PLB (which I always considered useful for finding a body at best).

[Beccara 25]

Sorry, Got techie heavy there

 

Yes, an EPIRB and PLB will not allow your boat directly to see a MOB, Only a dedicated MOB solution like Raymarine lifetag's which is not available anymore or an AIS SART beacon will allow your boat to directly be informed of the MOB event and where that MOB is at this moment

[Beccara 25]

I think i've got the main points but pardon me if i miss the mark.

 

First off when you talk about DSC you have to remember there are 2 systems. VHF and HF - VHF being what most of you know and use. I expect a few here know of HF. HF DSC is a complex topic for boats to use/have wherein i know alot of ICOM M80x HF sets aren't installed with the secondary antenna needed for DSC monitoring

 

NZ Coastguard do not monitor VHF DSC, Taupo Radio DO monitor HF DSC on 4/6/8/12/16mhz.

 

With AIS SART/PLB/EPRIB these devices serve one fuction and one function only. The unit's dont require any real external holes or recharging etc and as such they will always be more robust than a VHF handheld with GPS and DSC which is what you would need to have on the person falling overboard in order for the helm to receive their position rather than just simply marking on the plotter where the boat was at the time.

 

There is a quote here that i thinks fit's this topic well

 

"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away."

 

I know personally if i fell over i would want a EPIRB and AIS SART over an EPIRB and VHF DSC. The AIS SART is going to last longer and punch further since it's designed from the ground up to do 1 job and do it well.

 

I think you'll find aswell if you look at the coverage of VHF DSC overseas it's fairly limited. Most stations have a 30-40nm range or less. You will have black spots and alot of the coverage maps are done from a 1w radio 2meters above sea level. If you take into consideration you may be overboard in swell the range will become even more limited. VHF DSC is not really suitable for reliable announcement to land based assets that your in trouble

 

 

As for just relying on the 121.5mhz beacon, For non-SAR units even having an RDF would be rare and if they are you have to rely the crew to operate it correctly, In an emergency situation the stresses involved on people create well know issues with decision making. An AIS SART putting a big red X marks the spot on a screen if far far easier than using RDF to find someone and if the person left on board is not as well trained to well experienced it would be fairly hopeless.

 

​I hope that's someone clear and covered your points?

[rigger 47]

As stated earlier:

Some AIS PLB/MOB devices have VHF DSC capability as well - this is the alerting function that is req under GMDSS

Also not all AIS units (fitted on vessels) will recognize AIS PLBs as an emergency device or at all - so your onboard AIS unit may not alarm when it receives data from a PLB / MOB device or even display a target.

 

Also some onboard units will not display virtual AIS AtoNs. One brand of transmitter that many Garmin devices will not pick up is Vesper. Garmin hope to have a fix in about 12months last I heard.

 

So if buying AIS PLB's make sure your onboard AIS unit will pick them up.

[erice 732]

in theory

 

when the red distress button is pressed 

 

a VHF DSC will periodically send out digital bursts of data containing the vessel's pre-registered, MMSI, time and lat/long position (if connected to gps etc)

 

if nz coastguard does not monitor the freq and does not send the acknowledgement that cancels the transmission how long will it continue to broadcast?

 

other DSC VHF receivers turned on and within range

 

SHOULD record that data and alert the owner that a distress signal has been received and the data is recorded

 

they are then supposed to relay that information to CG

 

i wonder what'll happen when someone eventually presses the button in the hauraki gulf on a sunday afternoon?

 

will lots of owners be confused by squawking vhf?

 

will their radio displays show the information to be relayed?

 

presumably someone will call chan 16 and let CG know

 

will everyone then have to dig out their manuals to clear the distress message...

 

 

https://en.wikipedia.org/wiki/Digital_Selective_Calling

[Beccara 25]

Look, The one thing your forgetting Rehab is that safety, True safety - Not the warm fuzzy feeling safety, But true honest to god proven safety systems and processes are all about layers.

 

What happens when your crew isn't aware you've gone over and your not alert of in a state of mind to activate your handheld VHF DSC? What happens when the crew is in the water with you? Or any one of the other different situations you may find your self in which the crew arent in a position to fetch you?

 

Counting on and preparing for a crew rescue and as such neglecting the other layers of your safety systems is just plain sily. Sure the crew may get you back in most of the time but most of the time is not something that's really suitable when lives are at stake. You need a backup and your backup needs a backup system.

 

In the event that someone is knocked overboard and for whatever reason isn't picked up a combo of EPIRB and AIS Sart will allow for rescue with no input from the person overboard. This is the only thing at the moment that will, I'm yet to see a DSC handheld send out a DSC alert without input from the operator.

 

 

For the record, I count on my crew and then i count on the coastguard along with commercial mariners. Because of the lack of GMDSS for recreational boats ( a blessing and a curse) you can't event count on alot of people to even monitor 16 let alone DSC. I think if you triggered DSC in a big harbour the only people that would help/call you would be the CG and commercial ships.

 

As such I prefer to plan around what my crew will look for and for what CG and big ships.

[Island Time 1,239]

I agree rehab that NZ should have DSC.

 

I have read the DSC specs and I have not seen anything about automated emails for class D and E units (what most recreational boaters have)  Have I missed something?

 

There are multiple communications systems out there however,  that will allow Lat/long and even course and speed info to be appended to each outgoing email - Sailmail is one. If it is properly set up. Most are not.

 

The USCG says about DSC that about 60% of class D/E units have no mmsi programmed, and/or are not connected to a GPS unit, so they won't issue any call or distress signal. Later models often will not issue anything unless they have up to date GPS data, AND MMSI info programmed. This is to help avoid the myriad of "distress" calls via DSC without position or vessel details - completely useless.

 

The theory of DSC is great, but in practice, people being people, it is often not installed correctly, and or the operators do not understand it.

 

All that being said, my VHF has class D DSC, and it is connected to the GPS and programmed with my MMSI, which is being transmitted by my AIS transponder (class . I have never heard a DSC distress call in NZ.

 

But IMO if you have a newish VHF, and it has DSC, it should be connected, and tested.

[Beccara 25]

I'm done arguing Rehab, Clearly you fetish for DSC as the USCG has stated DSC is pretty bad,Most dont have GPS plugged in and even more dont have MMSI put in and thats in an area where DSC is monitored from land.

 

Fundamentally your method of safety is the polar opposite of what i think, Your placing a lot of reliance on your crew to get you back and your crew to communicate outwards. You put a lot of faith in recreational vessels around you over and above the CG and boats held to GMDSS spec's which is at a basic level where this conversation is falling apart.