Chuck Husick: Techno-Talk, May 2003 BoatUS Magazine -
Personal Locator Beacons (PLB's)
In the 20 years since SARSAT, the satellite-based 406 MHz EPIRB search and rescue system was launched in 1982, 14,471 people worldwide, including 4,440 in the U.S. have been rescued. As good as the system has been, it is about to become even more valuable.
Until now, the only 406 EPIRBs available for sale in the U.S. have been for use on a vessel or in a life raft. These devices weigh three to six pounds and are far too big to fit in a pocket. But smaller, lighter versions of the 406 EPIRB known as Personal Locator Beacons (PLB) have been available in some other countries for some time. The FCC has now acknowledged the worth of taking the search out of SAR for all individuals in urgent need of assistance, whether in the water or on land. About the time you read this issue of BoatUS Magazine, 406 MHz PLBs should be on store shelves.
The typical PLB is small enough to fit in a pocket (about two-by-three-by-six inches) and light enough (just over a pound) to be carried or worn without difficulty. All are waterproof, some will float. Like the 406 EPIRB, a PLB transmits simultaneously on both 406 MHz (to alert the listening satellites) and on 121.5 MHz to provide a homing signal for searching aircraft and ground parties. While the transmit power on 406 MHz PLBs is the same as the larger marine EPIRBs (five watts), the specified transmit time is 24 hours, half that of the EPIRB. Battery life is typically the same as that specified for the EPIRB, five years.
Each PLB’s transmission includes a unique identification number, therefore the buyer is required to register the unit with the SAR authorities. The simple one-page form can be downloaded from www.sarsat.noaa.gov. As with EPIRBs, PLB re-registration will be required every two years. Some PLBs provide an interface connection to an external GPS receiver, others have internal GPS receivers (position information is not displayed, it is only available for transmission as part of the mayday call).
The signals sent by EPIRBs and PLBs are monitored by both the COSPASS–SARSAT polar orbiting satellites and geostationary satellites. After a beacon is activated, about 20 minutes is needed for the data collection and processing required to determine the beacon’s location with an accuracy of about three miles. The appropriate rescue center is then alerted. A satellite that receives a beacon signal containing position information will immediately relay the information to the ground data processing system, alerting a rescue center in as little as three to five minutes, with position information accurate to about 100 feet.
Rescue center responsibility for an EPIRB or PLB call is assigned based on the location of the mayday. PLBs are likely to be carried by people hiking, boating or canoeing in remote areas. While the Coast Guard will continue to deal with all marine locations, signals originating inland will be handled by the SAR component of the National Park Service of the Department of the Interior.
Should you purchase a new PLB it’s important to learn the proper way to test your beacon. While the “old” style 121.5/243.0 MHz beacons could be tested by turning them on for one second during the first 5 minutes of every hour, this type of live transmission test is prohibited with the 406 MHz beacons. Although the precise test method varies among manufacturers, most 406 units contain a microprocessor that will check for normal function and announce the result by emitting a confirming beep and or flash of its LED or strobe light. Check the instructions that came with your beacon and be sure you follow them precisely. The SAR folks have enough to do without responding to an inadvertent mayday call.
Also, know the battery replacement date. While replacement batteries are not cheap, your life should be worth the cost of a proper replacement battery. Many manufacturers require that the beacon be returned to the factory for battery replacement. The retest of the unit and proper resealing to make the unit totally waterproof are well worth the price. Be sure the activating switch is in the “off and locked” position before you send it off for battery replacement. The SAR folks don’t want to have to come to the aid of a postal delivery truck on the Interstate.