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Sean, thanks appreciate the information. A couple of questions...the 121 EPIRB at the surface would have little range other than to aircraft where the line of sight might have a better angle to reach those aircraft or ships . But wouldn't the 406 EPIRB work well at the surface as it is broadcasting to satellites which are higher in the sky and have a broader range of reception due to there being several in the visual sky? Do you know of EPIRB's that are waterproof at depth and/or of a 406 that is within a reasonable price range for divers? I have a 121/243 aboard my dive charter boat but it is not something that could be taken by a diver to depth without flooding out. Also do you know of a source for a RDF that could pick up both VHF radio and EPIRB signals in a compact unit at a reasonable price? Captain Tom Mercier USCG Licensed Master Diver Medical Technician-ADV Nationally Registered Paramedic All Seasons Diving Company Dryden Michigan ---------- > From: Sean T. Stevenson <ststev@un*.co*> > To: John Chluski <undersea@ga*.ne*>; techdiver@aquanaut.com; William H. Howell <whowell@ic*.ne*> > Subject: Re: Of EPIRBs, bricks and coconuts. > Date: Wednesday, February 04, 1998 3:34 AM > > The Search and Rescue Satellite Aided Tracking System (SARSAT) makes use of several > orbiting satellites that carry equipment capable of detecting signals from certain types of > emergency transmitters such as Emergency Position Indicating Buoys (EPIB), Electronic Locator > Transmitters (ELTs), And Emergency Position Indicating Radio Beacons (EPIRBs). > > When an emergency transmitter sends a signal, it is received by one of the satellites which > in turn relays the signal back to a ground terminal or Local User Terminal (LUT) on Earth. Through > computer analysis of a phenomenon known as the Doppler effect, the location of the transmitter is > calculated and then passed on to the appropriate RCC (rescue coordination center). > > SARSAT has proven successful at detecting signals from these emergency beacons operating at > 121.5 / 243 MHz and ascertaining the location to within less than a 20 kilometer radius. However, > these types of beacons were not designed for use with satellites. To overcome problems with > frequency stability and interference from voice communications, beacons using 406 MHz have been > developed for use specifically with SARSAT. This frequency is exclusively assigned to satellite > aided search and rescue and can provide a position that is accurate to within a 2 kilometer radius. > The 406 MHz can also relay data messages such as the identity of the user. > > The time delay associated with a SAR response has little to do with the type of emergency > signal emitter used (other than the fact that most search and rescue units can not DF 406), but > rather the communications between the rescue coordination center and the search and rescue units > tasked to respond, the individual unit response time and the ability of the unit to DF the signal > where appropriate. The ability to efficiently DF a transmitter carried by a diver obviously is > affected by on scene weather conditions due to the transmitter being effectively at the waters > surface, so it is important to ensure that the batteries are good, and to be able to produce some > sort of visual or audible signal as well. > > -Sean T. Stevenson > > Seaman, Rescue Specialist > Canadian Coast Guard > Coxswain, Unit Prevention Officer, Training Officer > Coast Guard Auxiliary Unit 5 > Coastal Search and Rescue Instructor > Rescue Coordination Center, Victoria, BC > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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