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Old 03-05-2012, 10:44   #1
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EPIRB

As long as the 'test' works why change the battery?
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Old 03-05-2012, 10:50   #2
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Re: EPIRB

The standard batteries have a five year half life on the shelf. That is, if the EPIRB will run for 48 hours with a new battery, a five year old battery has only enough power left for it to run 24 hours. It is halfdead.

So, it will pass a test, it will work, the question is, do you want it to work for 48 hours? 24? 2? And the standard is to change them at five years, when they are half dead.
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Old 03-05-2012, 10:50   #3
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Re: EPIRB

How long do you want it to keep working when you trigger it for real?

"Test" doesn't measure the remaining battery capacity, it only checks some (not all) of the device for functionality.
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Old 07-05-2012, 13:03   #4
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Re: EPIRB

Curious, when the EPIRB is triggered. SAR get's an alert, the process then is put in place to come find me. Now, why do you need the EPIRB any longer. SAR is smart enough to know, if they cant get to me in a matter of hours that my position is going to change. Humor me. Don't they calculate the current and wind speeds and setout for my location based on that? Seems to me that that would be the case. And yes, the EPIRB being fully functioning would make it easier for them I guess. I plan on having a handheld radio with me to communicate with
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Old 07-05-2012, 14:01   #5
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Re: EPIRB

The satellites continue to fine-tune your Doppler-shift calculated position with every pass. If you have a GPS-EPIRB (GPIRB) your position will be updated. When SAR assets are homing in on your position they will use the EPIRB's 121.5 MHz emergency beacon. Drift rate and direction are imprecise at best, and it's a big ocean.

Why make it tougher for your rescuers? Your odds aren't all that great to start with.
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Old 07-05-2012, 18:17   #6
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Re: EPIRB

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Originally Posted by gpshephe View Post
Curious, when the EPIRB is triggered. SAR get's an alert, the process then is put in place to come find me. Now, why do you need the EPIRB any longer. SAR is smart enough to know, if they cant get to me in a matter of hours that my position is going to change. Humor me. Don't they calculate the current and wind speeds and setout for my location based on that? Seems to me that that would be the case. And yes, the EPIRB being fully functioning would make it easier for them I guess. I plan on having a handheld radio with me to communicate with
Gary,

I am afraid you must do some more reading before you head out into the blue yonder.

One can only calculate things they know the values of.

Did you hear of the homing signal from an EPIRB ever?

Love,
b.
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Old 07-05-2012, 18:37   #7
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Re: EPIRB

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Originally Posted by gpshephe View Post
Curious, when the EPIRB is triggered. SAR get's an alert, the process then is put in place to come find me. Now, why do you need the EPIRB any longer. SAR is smart enough to know, if they cant get to me in a matter of hours that my position is going to change. Humor me. Don't they calculate the current and wind speeds and setout for my location based on that? Seems to me that that would be the case. And yes, the EPIRB being fully functioning would make it easier for them I guess. I plan on having a handheld radio with me to communicate with
I was a USCG helo pilot for over 20 years...while you do make a point...it's the LAST place I would try to economize.

An EPIRB is the second by far greatest part of your survival system second only to a fully functioning, somewhat trained brain...
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Old 07-05-2012, 19:23   #8
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Re: EPIRB

"Now, why do you need the EPIRB any longer. SAR is smart enough to know,"
Gary, if you accept that SAR is smart enough to know anything, you might also consider that they must have reasons for wanting the continuing signal.

Sure, they calculate drift. What drift? What's your windage? What's your current drift? How much does each afffect you, in opposite directions? And if no one can reach you for twelve hours, because you are out of air range and the nearest ship is that far away, where do you want that ship to start looking for you? A couple of miles this way or that way, while you were drifting at 3 to five knots for twelve hours? Forty or sixty miles away from where the ship now is heading?

Now add temperature, because whatever battery life you have left, if the water or air is cold, that might be cut in half or worse. If it is hot, it might also be cut.

Do you want a SAR operation directed to where you ARE or where you MIGHT BE? Searching a hundred square miles of ocean (that's only a 10x10 box) just could take an extra hour or two--while you are either bleeding out or dying of hypothermia.

But if you're sure that won't be a problem, by all means, fifteen or twenty minutes of battery power just might work.

While equipment manufacturers may have only profit in mind, the guys who make the rules and operate the SAR system have usually put extensive thought into what they do and how they do it. Yeah, they've got budget constraints, but all in all they've put a lot of effort into a pretty incredible system.
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Old 07-05-2012, 19:42   #9
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Re: EPIRB

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Originally Posted by Chris Wren View Post
As long as the 'test' works why change the battery?
What is your boat worth?

What is your life worth?

What is worth of your crew's lives?

What does it cost to change a battery?
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Old 07-05-2012, 21:33   #10
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Re: EPIRB

Thank you all. didn't know the beacon broadcast on 121 as well. It also has GPS. Interesting. My initial post was really a devils advocate thing. I would not go out without one. Someone on the thread mentioned the battery thing and it got me to thinking about how the SAR actually used the signal. If the battery dies right after the initial signal, is it all in vain? I am very curious about the SAR process. If I can step up to the life raft what can I carry on board to help them. (EPIRB, Handheld VHF, Flares, Dye, Strobe light, whistle). My ditch bag's going to be full.
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Old 08-05-2012, 03:56   #11
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Re: EPIRB

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Originally Posted by gpshephe View Post
Thank you all. didn't know the beacon broadcast on 121 as well. It also has GPS. Interesting. My initial post was really a devils advocate thing. I would not go out without one. Someone on the thread mentioned the battery thing and it got me to thinking about how the SAR actually used the signal. If the battery dies right after the initial signal, is it all in vain? I am very curious about the SAR process. If I can step up to the life raft what can I carry on board to help them. (EPIRB, Handheld VHF, Flares, Dye, Strobe light, whistle). My ditch bag's going to be full.
No not in vain...as long as you got out one signal to suggest MAYDAY and a location...not sure about the rest of the world but the USCG will try every attempt to go to that location (factoring in drift) and see if someone is in trouble.

Set and drift is really only a guess without some onscene data...it's preferable to get it before the searchers arrive...so if your EPIRB sends out 3 or more positions before it dies..that should give a reasonable drift. If it dies...the every 5 hours or so of waiting really delays you being found quickly if at all (assuming yur drift is a knot or two...if less ...read good sea anchor on boat/raft...ten less search)

The whole point of an EPIRB/PLB is to take the "search" out of search and rescue....
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Old 08-05-2012, 05:27   #12
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Re: EPIRB

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Originally Posted by psneeld View Post
..........The whole point of an EPIRB/PLB is to take the "search" out of search and rescue....
Exactly plus of course, raising the alarm in the first place with not much more than a untrained flick of a switch!

Looking at some more numbers an EPRIB without an embedded GPS may take a couple of hours for a position to be determined and may have an error of 20 Km (12 miles). That gives a search area of say 1,200 sq Km (450 sq miles).

However an EPRIB with an embedded GPS will give a position fix within 2 minutes with an worst case accuracy of 100 m giving a search area of 0.03 sq Km and more likely will be accurate to 15 m giving virtually no search area at all.

I personally would much prefer to see an SAR helicopter fly in a nice straight line towards me and hover directly above rather than see one in the far distance conducting a grid (homing) search across an area of 1,200 sq Kms.

YMMV
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Old 08-05-2012, 06:54   #13
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Re: EPIRB

Here is a good read involving a real SAR case. Notice the time when the EPIRB signal was transmit and a position was determined by SAR. Are all your EPIRB registered with good contact information. Mine is.

Transportation Safety Board of Canada - MARINE Reports - 2005 - M05N0072
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Old 08-05-2012, 07:06   #14
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Re: EPIRB

It only costs about $275 to replace battery and test unit (approved installer listed on Ebay). It is totally irresponsible for an individual to put family/crew at risk and subject SAR services to substantial additional risk and cost by not taking basic safety precautions. Macho does not work on the water and can easily end up costing more than it saves.
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Old 08-05-2012, 08:40   #15
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Re: EPIRB

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Here is a good read involving a real SAR case. Notice the time when the EPIRB signal was transmit and a position was determined by SAR. Are all your EPIRB registered with good contact information. Mine is.

Transportation Safety Board of Canada - MARINE Reports - 2005 - M05N0072
Interesting read, so it took (in this instance) 1 hr 12 minutes to determine a position. A EPRIB with an embedded GPS would have decreased that to 2 minutes.

Point taken as to the need for good contact information on register.
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