Handheld DSC VHF vs. PLB for MOB

[SailFastTri]

I recently watched a YouTube vid about the DSC system and learned that the system uses all DSC-equipped boats as a relay chain to communicate with a shore station. Link is below, start at 8 minutes into the clip if you want to zero in on this info.

http://m.youtube.com/watch?v=M-f4nhnBThg

This makes a hand-held DSC-equipped VHF even more valuable as a rescue tool.... certainly for coastal sailors it's a "no-brainer" (knowing this) if deciding between whether to get a DSC-equipped VHF or a PLB. While PLB would be preferred offshore, the VHF would be my clear choice within about 30 NM of the coast.

I bought a floating hand-held VHF unit with built-in GPS a few years ago, which I clip to my belt if I leave the cockpit underway. It's the most likely to bring local help (local = faster).

[S/V Alchemy]

Originally Posted by SailFastTri

I recently watched a YouTube vid about the DSC system and learned that the system uses all DSC-equipped boats as a relay chain to communicate with a shore station. Link is below, start at 8 minutes into the clip if you want to zero in on this info.

This makes a hand-held DSC-equipped VHF even more valuable as a rescue tool.... certainly for coastal sailors it's a "no-brainer" (knowing this) if deciding between whether to get a DSC-equipped VHF or a PLB. While PLB would be preferred offshore, the VHF would be my clear choice within about 30 NM of the coast.

I bought a floating hand-held VHF unit with built-in GPS a few years ago, which I clip to my belt if I leave the cockpit underway. It's the most likely to bring local help (local = faster).

Not if you're injured or unconscious, but in an auto-inflating PFD. There are AIS-SART devices that work automatically, and even two years ago when I last looked at the options...well, there's a lot of options. But I think you have to look at it in terms of how, and when, you sail. If you are a solo sailor, Rule No. 1 is to stay clipped on and to rig jacklines. The most important part is to stay aboard.

Now, the GPS in the VHF is "nice to have" a) if you are in the water and not uninjured, because you need to be able to hit the red button AND (in some models) need to activate the GPS receiver. I leave mine generally off because it sucks down the battery when I just want a large-display handheld VHF that floats; and b) if you are within range of another boat or shore station within 3-4 NM, which is what five watts at 1 foot height will get you. As I said, it depends on your sailing grounds.

By contrast, a 406 Mhz GPS-equipped PLB needs antenna deploying, but there's just one button to push. Your location is seen and tracked for 24 hours or so. I favour having both, but if I fall in the middle of Lake Ontario at the moment, it's about 5C and I'll die pretty quickly. So get what you want, but make the first purchase a tether.

[ka4wja]

SailFastTri,
Sorry to say, but the info in that video is WRONG...
Please allow me to provide correct information...(from the IMO and USCG, etc.)
(While "local can equal faster", this video is wrong....and understand that I am a big proponent of DSC, but I wish to get the correct information out there!!)

Originally Posted by SailFastTri

I recently watched a YouTube vid about the DSC system and learned that the system uses all DSC-equipped boats as a relay chain to communicate with a shore station.

1) NO recreational vessels' VHF-DSC radios (Class D VHF-DSC radios) have ever had a "DSC-Distress Relay" function...and they cannot "relay" a DSC-Distress signal. (other than you picking up the microphone and transmitting a "mayday relay" on ch. 16...)

2) Some early versions (prior to 2000) of Class A VHF-DSC radios, which were designed to meet the GMDSS requirements of SOLAS ships, did have VHF-DSC Distress Relay functions....but since the frustrations of so many, on-and-on, round-robin, relays (and their interference with legitimate DSC Distress calls), the GMDSS rules were changed, so that DSC-Distress Relays are only allowed on the HF-DSC frequencies NOT on VHF-DSC, nor MF-DSC....(and these functions were removed from future Class A VHF-DSC radios)


3) The details of the DSC system, and of the radios' operations are available to all, on-line, for free....as well as a fair amount of info explained in the VHF-DSC radio's owner's manual....
(Sailfacsttri, I assume you do not have a VHF-DSC radio??)



4) From the 2001 IMO report, titled:
PROCEDURE FOR RESPONDING TO DSC DISTRESS ALERTS BY SHIPS

2.4 In no case is a ship permitted to transmit a DSC distress relay call on receipt of a DSC
distress alert on either VHF or MF channels.

2.5 Distress relay calls on HF channels should be initiated manually.

1 Introduction

The Sub-Committee on Radiocommunications and Search and Rescue (COMSAR), at its
fourth session (12 to 16 July 1999), decided that digital selective calling (DSC) relays of distress
alerts on all shipborne DSC equipment should be reduced and prepared a procedure for
responding to VHF/MF and HF distress alerts, given in flow diagrams 1 and 2, recommending
that it be displayed on the ship's bridge as A4 size posters. It also prepared the following
guidance.

2 Distress relays

2.1 Radio personnel serving on ships should be made aware of the consequences of
transmitting a distress relay call and of routeing a DSC distress relay alert to other than coast
stations (CS).
2.2 The number of unintended activations of DSC distress alerts and DSC distress relay alerts
creates extra work load and confusion to (M)RCCs and also causing delay in the response-time.
The original distress alert from a ship in distress should not be disrupted by other ships, by
transmitting a DSC distress relay alert.
2.3 Recommendation ITU-R M.541-8 on Operational procedures for the use of DSC
equipment in the Maritime Mobile Service identifies only two situations in which a ship would
transmit a distress relay call (distress relay alert):
.1 on receiving a distress alert on a HF channel, which is not acknowledged by a
coast station within 3 minutes. The distress relay call should be addressed to the
appropriate coast station (Annex 1, paragraph 3.4.2 and Annex 3, paragraph
6.1.4); and
.2 on knowing that another ship in distress is not itself able to transmit the distress
alert and the Master of the ship considers that further help is necessary. The
distress relay call should be addressed to "all ships" or to the appropriate coast
station (Annex 3, paragraph 1.4).
2.4 In no case is a ship permitted to transmit a DSC distress relay call on receipt of a DSC
distress alert on either VHF or MF channels.
2.5 Distress relay calls on HF channels should be initiated manually.
2.6 Compliance with operational and technical provisions above would prevent transmissions

of inappropriate distress relay calls.

DIGITAL SELECTIVE CALLING CLASSES

Class D:

Minimum DSC capability for VHF marine radios carried by recreational boaters, commercial fishing vessels, and other non-SOLAS regulated vessels. Class D required capabilities include:

• Distress call
• All-ships call
• Individual station call
• Use of distress, urgency, safety and routine priorities
• Nature of distress
• Distress coordinates
• Time for last (distress) position update
• Type of subsequent communications
• Radio VHF channel
• Display
• Receive distress relay and distress acknowledgment calls
• Alarm
• Distress acknowledgement (receive)
• Geographical area call (receive)
• Test call
• Test acknowledgement

5) Have a look here for more official details and info...

http://www.gmdss.com.au/images/pdf/25.pdf
(including flow charts)

Digital Selective Calling Classes

http://www.gmdss.com.au/ITU%20DSC%20tech%20spec.pdf




6) FYI, for procedures on HF-DSC....have a look here...
Special conditions and procedures for DSC communication on HF




7) As for a handheld VHF-DSC radio, being a good thing to have on-board....
Yes, we all agree that they are....
But, not for the erroneous reasons you saw mistakenly presented in the video you referenced...
{and, it is a certainty that every cruising sailboat should have a fixed-mount Class D VHF-DSC radio, connected with low-loss cable to a hi-quality VHF antenna mounted as high and in the clear as can be accomplished....}

If you need to signal a distress, it is not only common sense, but also part of the GMDSS plan, to use any/all means available!!


For recreational vessels (such as our cruising boats):
1-An EPIRB is considered your #1 Distress signaling device...

2 and 3-Followed by DSC Radio, MF/HF-DSC and VHF-DSC radio....and/or INMARSAT-C

Depending on who is making the list, the next two items "tie" for 4th place...or they may end up #4 and #5...
4-Voice radio (HF and VHF), marine and ham...
5-PLB's...




8) And Rule #1 (even when not sailing solo) is always "Don't Fall Off the Boat!"

Originally Posted by S/V Alchemy

If you are a solo sailor, Rule No. 1 is to stay clipped on and to rig jacklines. The most important part is to stay aboard.

Now, the GPS in the VHF is "nice to have" a) if you are in the water and not uninjured, because you need to be able to hit the red button AND (in some models) need to activate the GPS receiver. I leave mine generally off because it sucks down the battery when I just want a large-display handheld VHF that floats; and b) if you are within range of another boat or shore station within 3-4 NM, which is what five watts at 1 foot height will get you. As I said, it depends on your sailing grounds.

By contrast, a 406 Mhz GPS-equipped PLB needs antenna deploying, but there's just one button to push. Your location is seen and tracked for 24 hours or so. I favour having both, but if I fall in the middle of Lake Ontario at the moment, it's about 5C and I'll die pretty quickly. So get what you want, but make the first purchase a tether.

And, I agree with Alchemy....spend the first few hundred dollars on jacklines, tethers, harnesses, etc...and USE them....before worrying about what / how to signal a MOB distress...







I hope this helps clear up the confusion / erroneous info...

Fair winds..

John
s/v Annie Laurie

[gamayun]

Originally Posted by ka4wja

SailFastTri,
Sorry to say, but the info in that video is WRONG...
Please allow me to provide correct information...(from the IMO and USCG, etc.)
(While "local can equal faster", this video is wrong....and understand that I am a big proponent of DSC, but I wish to get the correct information out there!!)
1) NO recreational vessels' VHF-DSC radios (Class D VHF-DSC radios) have ever had a "DSC-Distress Relay" function...and they cannot "relay" a DSC-Distress signal. (other than you picking up the microphone and transmitting a "mayday relay" on ch. 16...)

I'm wondering if this isn't about semantics? The video talks about a "relay" happening without the captain of the vessel knowing, and you're saying that can't happen, but a group of us did a test recently in which a DSC test call was made and everyone's radio started to sound an alarm. You then have an option to get more info such as coordinates and to turn off the alarm. The way I understand how DSC-capable VHFs work is that it sends this signal to anyone within range and not only do the other boaters' DSC VHF radio continue to send along the signal, they could also become potential rescuers particularly if they are close enough. There is a lot of confusion about how it works, but it seemed pretty clear to me that it does act as a relay. Are you saying that once the signal goes through one of these boats, it does not act like a repeater to a land-based GMDSS? I attach a hand-held VHF on my PFD that can boost to 5 watts, for this very purpose, but of course staying on the boat is rule #1.

[transmitterdan]

It is not semantics. John is right. Distress relaying is not done by recreational DSC VHF radios.

If you are a single hander MOB then EPIRB is your best hope (but your odds are not very good IMHO). PLB is a distant second. AIS-SART could be useful in coastal locations with lots of other craft in the area. DSC VHF is not much use to a single hander MOB in open water far from other vessels.

However, if you are a MOB from a crewed boat then VHF DSC is worth considering IMO. This has been debated in other threads with dissenting views. A VHF DSC handheld attached to the MOB can be queried by the remaining crew and they can navigate right to the MOB location even if the MOB is unconscious. The handheld will report its GPS position in response to a position query from the ship's VHF without the MOB doing anything. A water activated AIS-SART can do this as well but they are very expensive and only transmit. With the DSC transceiver a conscious MOB can also tell the crew about his condition and they can reassure MOB they are coming back. A conscious MOB can also issue an all ships DSC alert or a MMSI specific call for help.

[IslandHopper]

My God is that Video still doing the rounds, someone forward the link to the USCG so they can pull it please....

The Australian Maritime Collage down in Tasmania used to play this to students doing there GMDSS course as a demonstration of the misinformation out there regarding DSC, as ka4wja states, no Class A VHF DSC equipment has had the relay function for years and Class D never had it....

[ka4wja]

Gamayum,
1) Although the title of this thread implies this is supposed to be a discussion about handheld vhf vs. a plb, for MOB...the premise of the original poster's thoughts / ideas on this subject are being based on FALSE / INCORRECT information...
So, I don't think this is really too much thread drift....

Let me preface this with the fact that DSC is not only part of the GMDSS, but the factual results show it DOES work very well...
And, in my opinion, NO cruising boat should be without a fixed-mount, VHF-DSC radio, connected with low-loss cable to a hi-quality VHF antenna mounted as high and in-the-clear as possible....(and I agree that VHF-DSC handhelds are also nice pieces of kit as well...)
But, this does NOT affect the facts that the above referenced video (and the understandings of SailFastTri and Gamayum) are incorrect!



2) Unfortunately this misunderstanding is quite common...
Please see specifics in red...

Originally Posted by gamayun

I'm wondering if this isn't about semantics? The video talks about a "relay" happening without the captain of the vessel knowing, and you're saying that can't happen, but a group of us did a test recently in which a DSC test call was made and everyone's radio started to sound an alarm. You then have an option to get more info such as coordinates and to turn off the alarm. The way I understand how DSC-capable VHFs work is that it sends this signal to anyone within range
This is not a semantics issue....the video clearly shows the presenter describing a DSC-relay, which does NOT happen...

Yes, a DSC All-Ships call (such as a DSC-Distress Call) DOES go to ALL other DSC radios within range....BUT...
But, these radios do NOT "relay" this call onto other radios/vessels...
Yes, some radios display information directly and some you need to select certain buttons to "pull-up" other info....but, this has nothing to do with the erroneous info about DSC-relaying...


As I wrote above, very early versions (prior to 2000) of Class A DSC-VHF radios ($2500+ VHF-DSC radios used for GMDSS compliance on SOLAS ships) did have this feature, but the GMDSS rules and IMO regs were changed (14 years ago!), and this featured was removed from all further Class A DSC-VHF radios, and was never available on any Class D VHF-DSC radios (radios costing a few hundred dollars, used by recreational boats)...

Understand that what I wrote above, and is clearly shown in the official IMO and USCG quotes/links, is actual fact....and the video presentation is WRONG...
Please read those quotes/links....


Yes, anyone can say/post anything on the internet, but when the page is from the USCG, and/or shows a pdf from the IMO, I think prudence would point you to conclude that the information is factual, and that a Youtube video is not a very legitimate source of factual info....(and yes, I have made/promoted my own Youtube videos about marine HF radio, and tried very hard to make them as factual as possible, with only a little "opinion", but I also mentioned that they are NOT a substitute for the owner's manual nor a complete understanding of HF communications...)




and not only do the other boaters' DSC VHF radio continue to send along the signal,
This is incorrect....
They do NOT "send along"/relay the signal...


they could also become potential rescuers particularly if they are close enough.
Yes, all vessels receiving a DSC-Distress message can be "potential" rescuers, but if you read the quotes/links above, you'll see that there are specific procedures to follow....mainly standing-by on the Voice communications channel (such as ch. 16 on VHF) and making ready to provide assistance/rescue for a few minutes, and logging/plotting vessel positions, while waiting for a shore station or RCC to respond to the DSC-Distress....and only then, if no shore station/RCC has responded, would you actually respond to the DSC-Distress call...(I have actually done this exact procedure myself a few times on HF-DSC, even while sitting at the dock...it WORKS!!!)




There is a lot of confusion about how it works, but it seemed pretty clear to me that it does act as a relay.
Sorry, but this is incorrect!!

Are you saying that once the signal goes through one of these boats, it does not act like a repeater to a land-based GMDSS?
Neither VHF-DSC, nor MF-DSC (2187.5khz), gets relayed to a shore station / RCC....
But, vessels within range of you, that are GMDSS equipped, CAN manually relay your distress to a shore station / RCC via INMARSAT and/or HF radio....but the DSC-VHF call is NOT relayed on...


If you are venturing outside of Sea Area A1 (coastal areas within range of VHF-DSC SHORE STATIONS), you should NOT rely on VHF radio (DSC nor voice) for signaling beyond your VHF range....
This is the reason that MF-DSC and more specifically HF-DSC radios are fitted (and required under the GMDSS / SOLAS rules)....
After an EPIRB, HF-DSC radios are one of the cost effective ways of being able to signal a Distress, when beyond VHF-DSC range....



I attach a hand-held VHF on my PFD that can boost to 5 watts, for this very purpose, but of course staying on the boat is rule #1.
Nothing wrong with a handheld DSC-VHF (except for the weight and bulk!), but understand that your range form that radio, when floating in the water is limited, especially when the sea state places you behind the waves....

I hope this further clarifies things???


Fair winds..

John
s/v Annie Laurie



P.S.
A bit "off-topic", but informative...
Regarding HF-DSC...NOT VHF-DSC...
Despite some "pooh-poohing" HF-DSC for direct signaling of other vessels, it IS not only acceptable but in some circumstances recommended by the USCG...
Here is the USCG page describing the HF-DSC procedures/recommendations...
http://www.navcen.uscg.gov/?pageName=DSCConditions

Just one quote from this page...

DSC distress alert should be sent to coast stations - e.g. in A3 and A4 sea areas on HF - and on MF and/or VHF to other ships in the vicinity.
[Note that the US, Australia, etc. have no Sea Area A2, and do not used MF at all...]
Ship-to-ship distress alert should normally be made on MF and/or VHF, using the procedures for transmission of DSC distress alert on MF/HF described earlier.

In special cases, for example in tropical zones, transmission of DSC distress alert on HF may, in addition to ship-to-shore alerting, also be useful for ship-to-ship alerting.

[S/V Alchemy]

Originally Posted by transmitterdan

It is not semantics. John is right. Distress relaying is not done by recreational DSC VHF radios.

If you are a single hander MOB then EPIRB is your best hope (but your odds are not very good IMHO). PLB is a distant second. AIS-SART could be useful in coastal locations with lots of other craft in the area. DSC VHF is not much use to a single hander MOB in open water far from other vessels.

However, if you are a MOB from a crewed boat then VHF DSC is worth considering IMO. This has been debated in other threads with dissenting views. A VHF DSC handheld attached to the MOB can be queried by the remaining crew and they can navigate right to the MOB location even if the MOB is unconscious. The handheld will report its GPS position in response to a position query from the ship's VHF without the MOB doing anything. A water activated AIS-SART can do this as well but they are very expensive and only transmit. With the DSC transceiver a conscious MOB can also tell the crew about his condition and they can reassure MOB they are coming back. A conscious MOB can also issue an all ships DSC alert or a MMSI specific call for help.

All true. I would add that there are directional systems for locating PLBs/EPIRBs: Automatic Radio Direction Finder for PLBs EPIRB Man Overboard Note this is for at the least a double-handed boat, and I don't endorse this brand or technique...it's just another way to get back to the MOB. It does make sense if you are high-latitude, where minutes in the water, even with a decent PFD, count.

[S/V Alchemy]

Originally Posted by ka4wja

A bit "off-topic", but informative...
Regarding HF-DSC...NOT VHF-DSC...
Despite some "pooh-poohing" HF-DSC for direct signaling of other vessels, it IS not only acceptable but in some circumstances recommended by the USCG...

John, when I got my VHF/SSB DSC certification a few years ago, we did indeed learn the difference between HF DSC relay (the red button on an ICOM M-802, for instance) and the VHF DSC all-ships on current Class D VHFs. Consequently, the MAYDAY RELAY of a vessel that might be, say, three NM from a handheld would be accomplished on Ch. 16 with plain old voice...but that alone could give the repeated positional information more bang for the rescue buck.

I've found since getting my new GX2200 that the power of the DSC setup is not really being fully exploited yet at the recreational sailor level. I expect to see more of it once out of the Great Lakes. I've also found that Ch. 16 in French waters is very quiet and very "professional", as you get fined for the sort of malarkey people pull on holiday weekends around here.

[goboatingnow]

Just to reiterate

(a) That USCG video is wrong and has been acknowledged so

(b) there never was repeat NEVER was any sort of automatic relaying of DSC alerts. even in HF it was a semi-automatic system and that has been discontinued and removed from most later software systems

(c) the purpose under GMDSS of a relay is to get the message to the shore station. Alerting in GMDSS means primarily telling a shot based MRCC NOT other vessels

The MRCC will then announce the distress to other vessels and will co-ordinate their response. This facet of GMDSS seems to be very mis-understood especially by US GMDSS users. In the old SOLAS conventions, there was no effective shore co-ordination and the primarily purpose of broadcasting maydays was to seek help from other vessels. Under GMDSS, the primary purpose of alerts is to inform a shore station

dave

[Oliver L.]

Everybody,

a slight thread drift - we are two on board, and whenever going offshore or overnight we strap a handheld VHF to the horseshoe ring. The rationale is as follows: Regardless as to who is left on board, he or she has to a) throw out the horseshoe, b) drop sails, c) start the engines, d) put the chart plotter on max so you can see the track and e) reverse on it. This will take time.

I know from losing hats etc that from the boat you have a very slim chance to see something in the water even if it's just 100 m away. On the other hand, the person in the water can see the mast for miles! And therefore the idea is that the person in the water will be able to direct you back to him/herself much easier.

If the person in the water is unconscious, we're out of luck - but then, you can't have it all...

Oliver

[Dockhead]

Originally Posted by SailFastTri

I recently watched a YouTube vid about the DSC system and learned that the system uses all DSC-equipped boats as a relay chain to communicate with a shore station. Link is below, start at 8 minutes into the clip if you want to zero in on this info.

This makes a hand-held DSC-equipped VHF even more valuable as a rescue tool.... certainly for coastal sailors it's a "no-brainer" (knowing this) if deciding between whether to get a DSC-equipped VHF or a PLB. While PLB would be preferred offshore, the VHF would be my clear choice within about 30 NM of the coast.

I bought a floating hand-held VHF unit with built-in GPS a few years ago, which I clip to my belt if I leave the cockpit underway. It's the most likely to bring local help (local = faster).

That video is infamous for being totally wrong! Ignore it!

[Dockhead]

Originally Posted by Oliver L.

Everybody,

a slight thread drift - we are two on board, and whenever going offshore or overnight we strap a handheld VHF to the horseshoe ring. The rationale is as follows: Regardless as to who is left on board, he or she has to a) throw out the horseshoe, b) drop sails, c) start the engines, d) put the chart plotter on max so you can see the track and e) reverse on it. This will take time.

I know from losing hats etc that from the boat you have a very slim chance to see something in the water even if it's just 100 m away. On the other hand, the person in the water can see the mast for miles! And therefore the idea is that the person in the water will be able to direct you back to him/herself much easier.

If the person in the water is unconscious, we're out of luck - but then, you can't have it all...

Oliver

I think that's actually a very good idea!!

I have always thought that a VHF with DSC would be the first thing I would want to have on my person if God forbid I went overboard. Your mayday will sound the alarm on your own vessel and all vessels around, who get your coordinates and thus can find you. As you correctly point out, that's the biggest challenge in a MOB situation.

The only problem is that my handheld is too bulky to keep on my person all the time . I really, really wish someone would make a really compact DSC VHF handheld which would fit in my lifejacket pocket.

AIS SART would also be a good thing to have, but for myself, I would really, really like to be able to talk to my crew or other potential rescuers.

Attaching it to the life ring is a clever idea. It requires, however, that someone sees the incident and gets the lifering over rather instantly. Much better to have the radio in your lifejacket pocket.

[goboatingnow]

the life ring idea has merits, but it relies on too many things going right, (a) the life ring has to be thrown over quickly and (b) the person in the water has to see it and be actually able to get to it.

Too many things to go wrong here i believe.


dave

[monte]

We just bought a couple of kannad R10 AIS MOB units. We fitted them to the lifejackets for auto activation, but theres not a chance in hell thay will work like that. The activation tag is too hard to pull off manually, let alone by a dodgy string arounf the inflatable jacket system. Anyway, auto activation would have been a bonus but I think it was more an after production brainwave.
Before buying them I contacted Raymarine and Kannad to make sure they would work with our e125 plotter. Raymarine said they thought it would just put a message on the screen saying AIS SART , with no Alarm or MOB features. They also told me the new e series plotters dont have an external alarm facility, but I was welcome to buy another plotter for inside the cabin so I can hear the alarm...
Kannad said they had no idea how it would work...
I tested it today in actual transmit mode, not test mode, and it does work as it should. Alarms go off on the plotter and the ST70 instruments. Also a position report and steer to position query box is activated. So far so good.
I think Raymarine are obtuse about it because they want to market their own version or sell their lifetag system. Maybe they are both afraid to admit they work in case they have a legal case of one not working one day. Either way, they do seem to work OK so far. I would like to modify the ease which the R10 activates so the lifejacket can activate it, but unfortunately its designed that it has to manually press the button as its released, which requires a bit of force. It would be better if it allowed the button to spring open when released.