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David Reinhard <reinhard@oc*.co*.au*> wrote: Hi Dave, I guess the first thing would be George's Rule number 1. Don't dive, or in this case, get on the boat with idiots who would leave you. I guess your concern stems from the fact that recently an Australian court found a dive boat operator "not negligent" for leaving two people 25 miles offshore to die on a Friday and not reporting them missing until Monday morning when their bags were found on the dive boat. But anyway some, info on EPIRBS. When you get one register it under the name of Caroline Kennedy, Address: Hyannis, Massachusetts. That way, if you ever use it, the entire United States Navy will drop what it is doing and rush to your aid. > some questions if anyone can help me: > > - roughly what size are they? They come in all sizes, some of the new ones are really small. The major US manufacturer is ACR Electronics. They have a web site at www.acrelectronics.com. They have a new personal 406 MHz EPIRB that weighs a little more than a pound (0.5 Kg) and will transmit for over 24 hours at -40 degrees (C and F). The battery is good for 5 and a half years unused. It is waterproof to 1 meter so a canister would be needed for diving. It transmits a 5 watt signal. > - what sort of depth rating would they have or do they require a housing? Most are designed to float at the surface, so a housing would be needed. > - would batteries be user replacable Sometimes, depends on the model. Many are not because the unit is sealed to make it waterproof. This is not something you use at the drop of a hat. In most countries it is illegal to use one unless a life is in danger or a vessel is sinking. They have seal on them that must be broken to activate them. That way they can prove you triggered yours and put you in jail or fine you big bucks or just make you pay for the costs of answering your distress call (BIG BIG bucks) if they determine that it was a false alarm. > - are these small units "powerful" enough to do the job (ie signal strength > - or does the signal go via satellite)? The ones you wany are 406 MHz EPIRBs and they are picked up by satellite. The older 121.5 MHz EPIRBs are much cheaper but are falling into disuse. Although the 406 MHz units usually also broadcast on 121.5 MHz because that's what search aircraft and boats can home in on with radio direction finders. The problem with 121.5 MHz units, and the reason they are not used much any more is that the satellite tracking of them is spotty at best. They are really only good when someone knows you are missing and they are out searching for you. The more expensive 406's broadcast to a satellite that you are in trouble and the satellite calculates your position within a mile or so. > - when an EPIRB is activated who actually receives the signal? With the 121.5 MHz units, anyone who may be listining and is within range of your transmitter. Since it will be on the surface of the ocean that limits the range severely. A satellite may or may not pick up the signal, but even if it does it just reports a general location of the signal to a Search and Rescue center. A 406 MHz unit anywhere in the world will be picked up by a satellite within 20 minutes or so and a position reported within 2 hours, worst case. They can guarantee this because the satellites are in polar orbit and cover 100% of the earth's surface. The report is routed by satellite ground receiving to a Search and Rescue Center in the USA. Once the position is established the Center notifies the nearest local rescue forces in that country or region. Those rescue forces can then send out by radio the coordinates and ask local shipping to assist as well. When you buy a 406 you register it in your name and your boat's name if applicable. You list several phone numbers for contacts. Before you go out you should let these people know you are going. That way when the Coast Guard calls to see if it is a false alarm your contacts can tell them when you left and maybe where you were going. The satellites that pick up the 406 signal can narrow it's location down to a smaller area than the older 121.5's, about 5 square miles So rather than getting a signal from an unknown source in a 100 square mile area (if you are lucky), the rescue center gets a signal that say "Bill Smith's EPIRB was triggered at Lat ABC.D Lon WXY.Z." The newest gadget is a 406 MHZ EPIRB with a GPS built-in, or that you can plug your separate GPS into. Rather than letting the satellites triangulate your signal, this ones tells the satellites your GPS coordinates. This can pinpoint your position to within 100 meters. The added advantage of this is that your position will be known within 20 minutes of the time you trigger the EPIRB because only one satellite is nedded to read your GPS fix. Without your GPS telling the satellite where you are, several satellites must pass over to triangulate your position. This can take up to two hours, worst case. So the rescue center will know it's you and they'll know you are in trouble within 20 minutes of your distress call, but they won't know where to send help until they get the position fix. That's why it is important to tell your contact people where you are going before you leave. > - are any/many divers using them (if not why not?) Probably not. The 406's cost $800 up. The 121.5s are a few hundred, but people just don't get left behind unless the operators are idiots. > - any particular brands better than others (any web sites)? I'm sure they are but to get certified by COSPASS/SARSAT they all have to be pretty good. ACR's are popular in the US, web site is: www.acrelectronics.com. You can also check boating sales centers like BoatUS, www.boatus.com, and West Marine, www.westmarine.com. Best Regards, Rick Fincher Thunderbird Technologies, Inc. rnf@tb*.co* -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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