As an emergency communications specialist, you need to know all about our present EPIRB systems, as well as the new proposal for a personal emergency locating band on 220 MHz. This article will bring you up to date on EPIRBs, plus review the new 406 MHz EPIRBs, and then tell you all about PELTS.
An EPIRB sends out a distinctive warbling tone on 121.5 MHz and 243 MHz. Mariners will manually activate a Class B EPIRB in times of emergency. Mariners may also operate float-free, automatic, Class A EPIRBs that self-activate in case of an immediate sinking. Most commercial vessels that carry passengers for hire are required to carry Class A and Class B EPIRBs on-board.
Aircraft pilots call the EPIRBs simply ELT, emergency locator transmitter. The aircraft ELT operates similar to a marine EPIRB, but it self-activates on sudden impact. It may also be manually activated, too. The big problem with marine and aviation EPIRBs is accidental activation. Over 98 percent of all EPIRB activations are simply false alarms..
This is a major problem to the COSPAS-SARSAT system that employs overhead satellites to relay EPIRB calls. The satellites don't know the real thing from a false activation, and rescue agencies must track down the EPIRB to find out whether it's a crash, or simply an accidental activation from a hard landing, or wet duffel bag.
Class A and Class B EPIRBs depend on a line-of-sight transmission to polar-orbiting satelltes, or to aircraft or search parties. And for the satellites to be effective, an EPIRB emergency coordination center must also be line-of-sight to that same satellite because satellites on Class A and B EPIRBs do not store and forward data. They will on the new 406 MHz system, but not Class A and Class B EPIRBs.
Class C EPIRBs were a giant flop in the marine community. They were designed to emit a warbling signal on Channel 16, 156.80 MHz. Channel 16 is such a mess these days that all of the interference actually sounds like an activated Class C EPIRB! Class C is a flop, and I can't remember a single rescue from a Class C signal on 156.80 MHz.
The new 406 MHz EPIRB is being adopted as a global standard, and provides much more accurate locations and coded search and rescue information. Category I 406 MHz EPIRBs float free and automatically activate, and Category II must be manually set on.
The big Improvement on 406 MHz EPIRBs is the ability to send up to a satellite encoded information about the type of vessel it was on, and possibly what the nature of the distress is in case of maual activation. The satellite will then store this information, and will downlink itself when commanded by a ground station in another part of the world. This means that the ground station does not need to be in simultaneous line-of-sight with the satellite when the EPIRB goes off. The encoded information will also allow ground stations to better track down false activations, and pinpoint the culprit.
406 MHz EPIRBs are just arriving on the scene, type-accepted by the FCC. It will still be several more years before the entire marine community fully adopts the 406 MHz EPIRB system. When it does, chances are traditional Class A and B EPIRBs at 121.50 MHz may be relegated for extinction -- or possibly only used as an ELT aboard small aircraft. Presently, there are 80,000 121.50 MHz EPIRBs in service aboard boats. There have been a few hundred good saves with the older EPIRB system, but literally thousands of false activations costing over millions of dollars to track down through search and rescue efforts. Hopefully, 406 MHz will cure this!
A brand new system called PELTS is under consideration by the Federal Communications Commission. It is designed for local tracking and search and rescue activities for hikers, skiers, and local mountain and river rescue squads. These tiny units, resembling a handheld walkie-talkie, would have capabilities of 2-way FM voice, emergency activation for homing capabilities, and a host of options to further its line-of-sight range to incoming rescuers.
Five frequency pairs in the new 220-222 MHz band are proposed for the PELTS system. Amateur radio operators are presently vacating these frequencies that have been reassigned to the land mobile radio service.
The personal ELT system would have 50 KHz of proposed spectrum, and this would allow hikers, as well as search and rescue agencies, plenty of "elbow room" to establish communications with lost parties with the PLT transmitter, and then home in on them using handheld radio direction finding equipment.
The new PELTS system would have nothing to do with satellites -- it would only be ground-based, so as emergency communicators, start thinking about homing capabilities on the new 220 MHz band for PELTS.