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EPIRB and external GPS interface questions

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EPIRB and external GPS interface questions

Old 08-24-2011, 07:37 AM
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Default EPIRB and external GPS interface questions

I am planning to purchase an EPIRB, and am looking at the ACR GlobalFix iPro (Category II - Model 2848) with the dual GPS capability, for use on a 24' center console. I would be trying to interface the EPIRB with a Garmin 4208.

My question is: How realistic is it to use the optical interface to an external GPS receiver in a center console? To succesfully interface with the 4208, is the EPIRB going to have to be wired down inside the center console? How can that be accomplished without negating the need to have the EPIRB available in a quickly-accessible location for deployment in an emergency?

I'm just trying to figure out if the dual GPS capabilities are really of value in this scenario. Any guidance will be much appreciated.
Old 08-24-2011, 04:26 PM
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ACR are very good units. You have to have an electrical connection to the optical output/interface to the EPRIB--so it needs to be fairly close and handy. It has to be hooked up each time you take the boat out (unless you leave the EPRIB in the boat) So, yes, you can interface it--and inside the console would work....BUT... Do you really want the EPRIB inside the center console if the boat goes down or catches on fire?

There were two rescue cases in the last several weeks where an auto EPRiB did not go off for some time when boats capsized. In both cases, the crew was found rapidly because of PLB, which were either on the life vest, or was grabbed by the navigator when they left the boat.

I can think of a number of other cases where the manual EPRiB went down with the boat. For that reason I use a PLB--in fact two of them (along with hand held VHF radio and a strobe) on my person. That way the distress beacon is with the crew member. When we were crossing oceans, we also carried two EPRIBS--one on the boat, the other in a ditch bag in the life raft.

Next issue, is the optical interface vs a cold start. The important issue here is that with the optical interface, and a "hot" GPS position, the first pass will have a good location. If you don't have this there will be a lag time of about an hour to get a rough doppler position from the satellite--but any satellite within 15 minutes should pick up the internal GPS of the EPIRP or PLB from its own GPS. There are multiple 406 mhz receivers on stationary satellites near the US Coast--and as soon as your unit transmits a GPS fix, it will go to Sat Sar. These stationary satellites cannot do a doppler fix of your position. There is always a latency time getting SAR mobilized. The Sat Sar satellite has to pick up the signal. (95% are false)--and then the national agency has to be notified. Next the phone calls are made, as the nearest (and that will be a very rough position from the first transmission reception) to be sure that you are out in the boat in the general vicinity of the distress call. Then finally a SAR unit is scrambled--either a chopper or boat--and a VHF radio call is made for mariners to be on the look out. This process usually takes half an hour or more. The fastest would be 15 minutes. By this time your internal GPS will have locked on--and subsequent transmissions will give the exact lat and long--and the SAR unit will then find you. Yes, you will get a more precise location on the first transmission if the IR interface is hooked up. But I doubt that it will make much difference in the time it takes to get a unit to your position. My personal thinking is that it is more important to have a PLB on my person, where it can always be utalized, rather than a hot fix EPRIB hidden away, where you might not be able to get it. In either case, it is important to have an internal GPS--and best if you can use the optical interface. Best would be both...
Old 08-24-2011, 05:59 PM
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The EPIRB GPS /Optical interface cord is about 6 feet long. I have the same ACR EPIRB on my boat. I mount it on the side of the console (outside), within easy reach of everyone. The cord runs through a small hole to the inside of the console and connects with the 3' long chartplotter connection. So, if you can get the EPIRB to within 9' of the chartplotter, it is easy to hook up and I do that. Now, to the point above, the EPIRB will probably get its own fix within 15 minutes and probably a lot sooner and no one can get to you that fast anyway. So, 99% of the time, it really wont matter. The only time it will matter is if your EPIRB battery is low, malfunctions, etc and you only get out the one transmission, at least it will send a hot GPS coordinate. So, it is a small safety feature that will probably never be used, but it is 2 simple wires, so why not hook it up anyway.
Old 08-25-2011, 06:32 AM
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Bob and Salty G -

Thank you for your replies. As always with fellow THT members, both were very helpful in helping me assess this situation.

Salty G - any chance you have a photo of your EPIRB/external GPS connection that you'd be willling to share? I'm just trying to envision if/how I could set up a similar arrangement on my boat.
Old 08-25-2011, 03:57 PM
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Hi Bongo
Sorry, no picture. I have the Epirb mounted in the white bracket that comes with it, on the front of my center console, under the top of the helm, so it is open and accessible, but out of the way. then just the small optical cable sits on top of the epirb and I just have a small hole that the wires runs into my dash and just connects to the chartplotter. 2 wires, a positive and negative of the chartplotter NMEA 0183 output lines. Hope that helps.

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