EPIRB PLB vs MOB Beacon

[atnan]

I agree this is a bit vague, but I read it to say that the device is sending out an MOB AIS signal.

Yeah, specifically the PLB3 is an AIS-SART/MOB device (MMSI starts with 972), and it broadcasts “MOB ACTIVE” messages and position reports when activated. Here’s the gory details:

M.1371 : Technical characteristics for an automatic identification system using time division multiple access in the VHF maritime mobile frequency band

AIS-enabled chart plotters can treat MOB targets differently; one might show a ship icon with the text “MOB”, another might show the official icon for a SART, and another might show the symbol and play an alarm. You can figure out what your chart plotter will do by performing a test, which will broadcast “MOB TEST” messages instead of an active alert.

Unlike the MOB1 the PLB3 doesn’t have DSC, so the above mechanism is how it’s broadcasting a distress signal to AIS-capable nearby boats in addition to the 406 MHz broadcasts to SAR.

 

[JC522]

Unlike the MOB1 the PLB3 doesn’t have DSC, so the above mechanism is how it’s broadcasting a distress signal to AIS-capable nearby boats in addition to the 406 MHz broadcasts to SAR.

Given all that and assuming that there is an EPIRB onboard, which one would you prefer for your PFDs when you are sailng on Lake Michigan, MOB1 or PLB3?

 

[CFS Klopas]

Given all that and assuming that there is an EPIRB onboard, which one would you prefer for your PFDs when you are sailng on Lake Michigan, MOB1 or PLB3?

AIS is worthless on Lake Michigan, no one uses it.

 

[JC522]

AIS is worthless on Lake Michigan, no one uses it.

I don't agree. I'd say about 20% of the boats I see on the lake are transmitting AIS. I don't know how many are receiving, but most of my friends, mostly in 35 to 45 foot boats, have AIS receivers or transcievers. Compare that to DSC where every VHF radio sold since 1999 has it. That's why I prefer the MOB1.

 

[atnan]

Given all that and assuming that there is an EPIRB onboard, which one would you prefer for your PFDs when you are sailng on Lake Michigan, MOB1 or PLB3?

I prefer the MOB1 + a Garmin InReach Mini. Advantage of the InReach is I can legally use it on land or sea, it can send text messages, and friends/family can check in on me on a map.

 

[Howler]

Distress signaling is the sole purpose of DSC.

That's not correct. DSC is also used for routine communication between ships.
There are four priorities of DSC messages: Distress, Urgency, Safety and Routine
DSC messages can be sent to All Ships, Geographic Area, Group, and Individual.

Making a Routine, Individual call is somewhat like placing a phone call: you enter the MMSI number of the ship you want to contact and the channel you want to talk on; the receiving ship's radio beeps to indicate an incoming DSC call; upon acknowledgement by the receiving ship, both radios switch to the requested channel, and you talk.

[edit: The Wikipedia article isn't bad: https://en.wikipedia.org/wiki/Digital_selective_calling]

 

[Howler]

I don't agree. I'd say about 20% of the boats I see on the lake are transmitting AIS. I don't know how many are receiving, but most of my friends, mostly in 35 to 45 foot boats, have AIS receivers or transcievers. Compare that to DSC where every VHF radio sold since 1999 has it. That's why I prefer the MOB1.

That there are lots of DSC equipped radios out there on the water really doesn't do you much good with a MOB1. When configured for the Canada, the MOB1 will not transmit any DSC message at all. When configured for the USA, the MOB1 will transmit a DSC message only to the radio whose MMSI number has been programmed into the MOB1, until 30 minutes after activation, at which point it will also alert VHF radios belonging to the group whose MMSI number has been programmed into the MOB1.

 

[JC522]

That there are lots of DSC equipped radios out there on the water really doesn't do you much good with a MOB1...

OK, DSC has some other capabilities...thanks for that info.

MOB1 will also do an All Ships Distress Alert if you press and hold the ON button for 5 seconds.

So which is the best device for the stated venue, PLB3 ot MOB1?

 

[us7070]

This thread should be deleted.., as a public service

 

[Howler]

MOB1 will also do an All Ships Distress Alert if you press and hold the ON button for 5 seconds.

Not in the USA or Canada if properly and legally configured.

So which is the best device for the stated venue, PLB3 ot MOB1?

For my 'druthers, I'd take the MOBI with AIS+DSC. The DSC will make an annoyingly loud alert tone on your own boat's VHF, which will alert your crewmember who was maybe below decks when you fell over the side; that's probably your best first-line rescue opportunity. The DSC also might or might not, depending on what kind of electronic integration you have on board, show your location on your own boat's chartplotter. At the same time, the AIS will light up a target on the chartplotter display of those boats nearby who have AIS integrated with their chartplotters. Which isn't everyone, but one or two boats trying to rescue you is better than none. Again, depending upon the age and configuration of those boats' electronics, it might even sound an alert tone and show a red or flashing target labeled "MOB".

The PLB3 won't do the DSC thing listed above, it will do the AIS thing, and, additionally, it'll transmit a 406 MHz message to a satellite, which will in turn light up a message at some control center somewhere, where the staff will probably first call the phone number registered to the device to ensure it's not a false alarm, and then dispatch a message to the nearest USCG facility, who will probably try to raise you on the radio and then, maybe if that doesn't work, dispatch SAR assets. I'm guessing in the lakes, unless you're wearing exposure gear, you're probably dead from hypothermia before anything useful happens via satellite.

 

[JC522]

Not in the USA or Canada if properly and legally configured.

I'm attempting to verify that with ACR tech support.

 

[Howler]

I'm attempting to verify that with ACR tech support.

For the MOB1, it's in the manual, page 12 http://oceansignal.com/wordpress/wp-content/uploads/MOB1-user-manual2.pdf

 

[JC522]

For the MOB1, it's in the manual, page 12 http://oceansignal.com/wordpress/wp-content/uploads/MOB1-user-manual2.pdf

You are probably right, but...

Regarding long press All Ships alert per MOB1 manual: "Applies only in countries where DSC All Ships Alerts are allowed." Are they allowed in the US?

From wikipedia: "Class D VHFs, used for most leisure vessels, can send distress, all ships urgency, all ships safety and individual alerts/announcements...."

From Panbo.com: "...note that in U.S. waters, the beacon can also send out a DSC group call after 30 minutes and in many areas the person overboard can manually initiate an all ships distress alert...." https://panbo.com/testing-ais-mob-beacons-acr-dsc/
Still not totally clear because he adds "in many areas". Is the US one of those areas?

From International Telecommunications Union, Radiocommunications Study Group Recommendation M.541, Operational Procedures for the use of Digital Selective-Calling (DSC) Equipment in the Maritime Mobile Service https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.541-10-201510-I!!MSW-E.docx :
Section 2.1 "The transmission of an urgency message is thus carried out as follows:
– select the appropriate calling format on the DSC equipment (all ships (VHF only), geographical area or individual)..."
Section 3.1 "The DSC safety call may be addressed to all ships (VHF only), ships in a specific geographical area or to a specific station."

Still waiting for ACR to respond with a definitive answer.

 

[Howler]

"Applies only in countries where DSC All Ships Alerts are allowed." Are they allowed in the US?

From Panbo.com: "...note that in U.S. waters, the beacon can also send out a DSC group call after 30 minutes and in many areas the person overboard can manually initiate an all ships distress alert...." https://panbo.com/testing-ais-mob-beacons-acr-dsc/

Still not totally clear because he adds "in many areas". Is the US one of those areas?

I don't understand where the confusion is coming from. The list of what countries allow what DCS calls is right in the panbo article you're quoting from, about one paragraph above the line you're quoting, and it answers your question.

 

[sculpin]

I think the distinction between the different units isn't that confusing.
1) EPIRB - this is the yacht's distress beacon, an EPIRB is longer life (battery) than the others. Available in manual activation as well as automatic deployment - suited for a vessel.
2) personally worn devices, of which there are two flavors - the PLB, and the MOB device. Which you wear will depend on how you think you might be rescued. I sail by myself fairly often, so a MOB device would not be preferred as it assumed your host boat is coming back for you. A PLB would be a better choice as it sends a more widely received call for help.
If I'm sailing with crew then a MOB device would be preferred as the best potential rescue is the boat I fell off of. This assumes that if the host boat sinks we can activate the EPIRB...

The MOB device transmitting AIS or DSC is a matter of different ways to skin the same cat. AIS assumes boats in the area have AIS receivers, and DSC assumes we all have modern VHF radios that are turned on - both assumptions have limits as not everyone has AIS and not everyone turns on their radios. I prefer the AIS as it shows up clearly on a chartplotter.

 

[JC522]

I don't understand where the confusion is coming from. The list of what countries allow what DCS calls is right in the panbo article you're quoting from, about one paragraph above the line you're quoting, and it answers your question.

It seems curious that the DSC on my VHF can send an All Ships alert and the MOB1 can't. Panbo quotes ACR's FAQ and then says something that possibly conflicts with it. Given that and the other sources that I quoted, I'd like to see confirmation one way or the other from a source other than the ACR FAQ.

 

[Howler]

It seems curious that the DSC on my VHF can send an All Ships alert and the MOB1 can't.

It doesn't seem all that curious to me that the regulations governing a VHF radiotelephone device versus a crew-overboard device would be different. One place to start would be the ITU recommendations, which do not in and of themselves have the force of law, but may be useful. I don't see the conflict between ACR's FAQ and anything in the Panbo article.

I think I've contributed everything that I reasonably can to this thread; I'll quit posting to it.

 

[JC522]

It doesn't seem all that curious to me that the regulations governing a VHF radiotelephone device versus a crew-overboard device would be different. One place to start would be the ITU recommendations, which do not in and of themselves have the force of law, but may be useful. I don't see the conflict between ACR's FAQ and anything in the Panbo article.

I think I've contributed everything that I reasonably can to this thread; I'll quit posting to it.

Thanks Howler. I'll continue to pursue a response from ACR. If I get anything definitive I'll post.
Thanks to all who bit, and apologies to everyone else. In my next post I'll ask which is the best anchor....

 

[Howler]

Thanks Howler. I'll continue to pursue a response from ACR. If I get anything definitive I'll post.
Thanks to all who bit, and apologies to everyone else. In my next post I'll ask which is the best anchor....

Yeah, I had drafted a somewhat colorfully abrasive "fuck off, troll" type of response several messages back in this thread, but, as lately I've been trying out the practice of assuming people are sincere, I chose not to post it.

 

[George Dewey]

You program the MMSI of the boat you are on into the MOB1, so it can send an alert specifically to that device just like one boat can call another boat directly if it knows the other boat’s MMSI.

Very good that you posted this. I have known excellent sailors who have been doing offshore for years but didn't realize it's necessary to program their MOB beacons.

So which is the best device for the stated venue, PLB3 ot MOB1?

I think the OP was asking about the Great Lakes, but the answer to this question is probably, it depends. If someone is an offshore or ocean racer who does races subject to US Sailing SERs and such, then the boats are likely (but absolutely not guaranteed) to have reasonably current plotters with AIS SART capability so the PLB3 is the winner. If you're just out sailing around, you might be better off with the DSC so the MOB1 is the winner.

Sadly, when you're just out sailing around, a lot of people have older equipment and turn their radios off.

As for alarms, my B&G Zeus 3 has the ability to turn SART alarms off, which I find odd especially since off is the default. It also has the ability to connect to an external siren, which I'll install before Spring.

But as many have alluded to, this is all great technology which most people, even skilled ones, have no idea how to use. If people remember one thing from this thread, I would suggest it be that they need to program the MMSI of the boat they are on into the MOB transmitter.