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Old 12-12-2013, 04:10   #1
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Handheld VHF with GPS/DSC or Personal AIS?

Hello all,

Trying to get some ideas regarding safety MOB equipment and what's currently out there.

I've ran across some very small personal AIS devices which are very good.
But also some newer handheld VHF radios with GPS built in and DSC.

Would I be right in thinking that these could in effect work in the same way? I.e. if you hit the DSC distress button if you fell overboard your boat (and others in range) would pick this distress call up, and with it your location? Would modern chart plotters then display this position aiding MOB recovery?

The VHF radio obviously has a lot of other benefits in so much that you'd then be able to use it to create an audio link with whoever's trying to pick you up, etc.

Any thoughts on this would be most welcomed.

Regards,
Simon
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Old 12-12-2013, 05:11   #2
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Re: Handheld VHF with GPS/DSC or Personal AIS?

It will work as you imagine, but can you be sure of always having it on you in case you go over? DSC handhelds are pretty bulky.

I very much wish that a really tiny one with a folding antenna and long-life lithium AA cell power would be made, exactly for our life jackets.

I do keep a PLB lanyarded into my life jacket -- an ARC ResQLink which is pretty tiny. But it would be nice to have a DSC VHF or an AIS beacon as well, since the mother ship cannot directly receive the PLB signal.
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Old 12-12-2013, 05:16   #3
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Re: Handheld VHF with GPS/DSC or Personal AIS?

Waiting for some company to combine the three.

AIS would be great to have as its small enough to have in the pocket all the time.
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Old 12-12-2013, 07:15   #4
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Re: Handheld VHF with GPS/DSC or Personal AIS?

Also, you must be conscious and able to turn on the vhf and activate a dsc call.

Mark
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Old 12-12-2013, 15:48   #5
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Re: Handheld VHF with GPS/DSC or Personal AIS?

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Originally Posted by colemj View Post
Also, you must be conscious and able to turn on the vhf and activate a dsc call.

Mark
This is very true. I know some of the AIS devices can be hooked up to auto inflation life-vests for this very reason.

Just seems like a lot of kit to be strapped to a life-vest...

AIS
VHF
PLB

Is that what people do though? Carry all three?

I totally agree with an earlier poster... first company to combine all three will make a killing!
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Old 12-12-2013, 17:07   #6
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Quote:
Originally Posted by simonpickard View Post

This is very true. I know some of the AIS devices can be hooked up to auto inflation life-vests for this very reason.

Just seems like a lot of kit to be strapped to a life-vest...

AIS
VHF
PLB

Is that what people do though? Carry all three?

I totally agree with an earlier poster... first company to combine all three will make a killing!
Won't happen , battery requirements are too different. And anyway , why carry a personal VHF. AIS SARTS can be made very compact , PLBs not so easy with the COSPAS SARSAT requirements. VHF s will always be a certain size just to accommodate speakers and rechargeable batteries.

In my opinion an AIS SART is the best unit PLBS are not really a good substitute. In the ocean GMDSS tries to limit max rescue time to 4 days. I don't think you'd survive that long , so a PLB really isn't a whole lot of use. Also since the PLB is not registered to a ship /boat there may be no way for an MRCC to contact the yacht to tell them where the Mob is.

I have a PLB myself , but I doubt there are really much use
Dave
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Old 12-12-2013, 19:28   #7
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Re: Handheld VHF with GPS/DSC or Personal AIS?

"In my opinion an AIS SART is the best unit PLBS are not really a good substitute."

I guess that depends if anyone's within AIS range. If they aren't, or your own boat misses the alert, bad luck.

I agree it's an oversight that PLB's can't somehow "phone home" to their local boat- as this in most cases will be the closest ship. Why that wasn't integrated into the original spec somehow is a shame.
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Old 12-12-2013, 19:45   #8
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Quote:
Originally Posted by simonpickard View Post
"In my opinion an AIS SART is the best unit PLBS are not really a good substitute."

I guess that depends if anyone's within AIS range. If they aren't, or your own boat misses the alert, bad luck.

I agree it's an oversight that PLB's can't somehow "phone home" to their local boat- as this in most cases will be the closest ship. Why that wasn't integrated into the original spec somehow is a shame.
Well in reality PLB position determination can take over an hour. Current protocols mean that the ground stations wait for a Doppler pass before declaring a distress. Furthermore typically the MRCC attempts to contact the land based reference , to determine what's what. All this means that several hours can go by before any rescue asset attempts to locate you. Offshore that asset could take days.

Given round here , you'll be dead from hypothermia in about 40 mins. PLBs make very dubious MOB devices. Most likely they'll direct rescuers to your body.

Hence AIS SARTS make much better MOB alerting devices. Because your best chance of rescue comes from the boat you just fell off of.

PLBs are just a version of an EPIRB , not a MOB device. ( which is why there was no local broadcast alarm idea )

Dave
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Old 12-12-2013, 19:57   #9
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Re: Handheld VHF with GPS/DSC or Personal AIS?

Makes sense Dave, so I guess I'm back at my original question. Why would you pick an AIS over a DSC VHF radio with GPS if both can alert the local boat?

Does it mainly come down to size?
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Old 12-12-2013, 20:10   #10
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Quote:
Originally Posted by simonpickard View Post
Makes sense Dave, so I guess I'm back at my original question. Why would you pick an AIS over a DSC VHF radio with GPS if both can alert the local boat?

Does it mainly come down to size?
There are several issues with dsc mob altering. Firstly GMDSS protocols are designed that in the first instance DSC alerts are handled by a land based station , hence a dsc alert will in effect cause everyone to wait for the coast guard station to cancel the alert and assume control of the rescue.

Secondly most leisure vessels do not have class A or B DSC sets there cannot respond correctly to a DSC alert.

Thirdly GMDSS protocols require that voice backup be used

Hence a DSC mob , in reality is a complete VHF and really requires a button interface , display and user input to use.


Contrast that with AIS SARTs, where the system can be much smaller ( McMurdos is really tiny) can work completely automatically without any user input and there much more chance that your boats AIS receiver is always on , whereas off shore your radio isn't.

Hence in my view AIS SARTs are excellent MOB alert systems, whereas I believe no one is going to bother with DSC MOB alerting systems.

Dave
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Old 13-12-2013, 07:27   #11
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Re: Handheld VHF with GPS/DSC or Personal AIS?

WRT the OP, I would not bother with the combination units. I bought the Standard Horizon HX-851 about a year ago and would not buy it again.

My thinking was that it would be good for the ditch bag, and having another backup GPS seemed like a good idea. In practice, the battery life is just too short, and the radio is a bit cumbersome.

I just turned it on (or tried to) to check the GPS fix time since I am n the Bahamas and had not turned it on since I went out the inlet in Beaufort NC... So I thought it would be a good test. Well, despite having a full charge it is dead now. Not something I plan to put back into my ditch bag.
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Old 13-12-2013, 07:38   #12
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Re: Handheld VHF with GPS/DSC or Personal AIS?

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Originally Posted by goboatingnow View Post
In my opinion an AIS SART is the best unit PLBS are not really a good substitute. In the ocean GMDSS tries to limit max rescue time to 4 days. I don't think you'd survive that long , so a PLB really isn't a whole lot of use. Also since the PLB is not registered to a ship /boat there may be no way for an MRCC to contact the yacht to tell them where the Mob is.

I have a PLB myself , but I doubt there are really much use
Dave
I agree that PLB is not really a substitute for a device which will directly signal the mother ship.

However, I think PLB is probably better than you think. For one thing, anywhere in range of UK or French rescue helicopters, I think you may get rescued directly and rapidly and more efficiently than the crew on the mother ship can do it.

For another, I think that if you can call the Coast Guard somehow from the mother ship (sat phone? SSB?), they will be getting the signal and can read you the coordinates. Vastly better than nothing, I think.
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Old 13-12-2013, 07:40   #13
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Re: Handheld VHF with GPS/DSC or Personal AIS?

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Originally Posted by s/v 'Faith' View Post
WRT the OP, I would not bother with the combination units. I bought the Standard Horizon HX-851 about a year ago and would not buy it again.

My thinking was that it would be good for the ditch bag, and having another backup GPS seemed like a good idea. In practice, the battery life is just too short, and the radio is a bit cumbersome.

I just turned it on (or tried to) to check the GPS fix time since I am n the Bahamas and had not turned it on since I went out the inlet in Beaufort NC... So I thought it would be a good test. Well, despite having a full charge it is dead now. Not something I plan to put back into my ditch bag.
A good solution to that is an AA battery tray and a bag of long-life Lithium AA batteries. That's what I do, and I consider the HX-851 an important part of the grab bag kit, despite the drawbacks you mention.
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Old 13-12-2013, 07:48   #14
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Re: Handheld VHF with GPS/DSC or Personal AIS?

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I agree that PLB is not really a substitute for a device which will directly signal the mother ship.

However, I think PLB is probably better than you think. For one thing, anywhere in range of UK or French rescue helicopters, I think you may get rescued directly and rapidly and more efficiently than the crew on the mother ship can do it.

For another, I think that if you can call the Coast Guard somehow from the mother ship (sat phone? SSB?), they will be getting the signal and can read you the coordinates. Vastly better than nothing, I think.
There is actually quite a long delay in validating EPIRB/PLB signals, because the assumption is that response in hours is good going. for an MOB in cold waters around the UK , response in minutes can be needed. With a PLB, the boat might not ever know , or be hours away when it finally discovers the EPIRB/PLB alert.

Futhermore , and I've seen it happen, is if there is intermittent satellite communications with the PLB, which can happen if the user is in the water, then often the coastguard will send out a PAN PAN rather then immediately activate a rescue. GMDSS protocols actually specific that you must have TWO independent means of activating distress alert in each sea area. SO often there is an expectation that another GMDSS alert will be triggered.

COSPAR SARSAT was never really designed to respond in minutes , for MOBs by far the best method is clearly AIS SARTS. IN my view purely for MOB location, PLbs are a way of guiding rescuers to your body.

dave
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Old 13-12-2013, 11:48   #15
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If I am mainly concerned with own boat rescue in cold waters it is reasonable to assume the boat will be equipped with proper DSC reception equipment. And it is reasonable to assume the DCS radio is interfaced to chart plotter to show location of DSC equipped MOB. If these assumptions are not true that could be corrected by the owner before leaving port.

I think it would be possible for a clever software person to rig a DSC alert to automatically drive the auto pilot back to ansingle handed MoB. I suspect someone has done this or it will eventually be possible to do it.

A really clever software person could rig an onboard EPIRB and/or AIS to send an alert and give location of DSC equipped MoB. The mothership merely has to be within VHF range.
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