All You Ever Wanted To Know About Emergency Position Indicating Radiobeacons (Epirbs)
Types of EPIRBs
Emergency position indicating radiobeacons (EPIRBs), devices which cost from $200 to about $1500, are designed to save your life if you get into trouble by alerting rescue authorities and indicating your location. EPIRB types are described below:
121.5/243 MHZ. Float-free, automatically-activating, detectable by aircraft and satellite. Coverage is limited. An alert from this device to a rescue coordination center may be delayed 4 - 6 or more hours.
121.5/243 MHZ. Manually activated version of Class A.
VHF ch 15/16. Manually activated, operates on maritime channels only. Not detectable by satellite. These devices are being phased out by the FCC and are no longer recommended.
121.5/243 MHZ. Similar to Class B, except it floats, or is an integral part of a survival craft.
406/121.5 MHZ. Float-free, automatically activated EPIRB. Detectable by satellite anywhere in the world. Recognized by GMDSS.
406/121.5 MHZ. Similar to Category I, except is manually activated. Some models are also water activated.
1646 MHZ. Float-free, automatically activated EPIRB. Detectable by Inmarsat geostationary satellite. Recognized by GMDSS. Not sold in the U.S.
121.5/243 MHz EPIRBs
These are the most common and least expensive type of EPIRB, designed to be detected by overflying commercial or military aircraft. Satellites were designed to detect these EPIRBs, but are limited for the following reasons:
1.Satellite detection range is limited for these EPIRBs (satellites must be within line of sight of both the EPIRB and a ground terminal for detection to occur),
2.Frequency congestion in the band used by these devices cause a high satellite false alert rate (99.8%); consequently, confirmation is required before search and rescue forces can be deployed, 3.EPIRBs manufactured before October 1989 may have design or construction problems (e.g. some models will leak and cease operating when immersed in water), or may not be detectable by satellite. Such EPIRBs may no longer be sold,
4.Because of location ambiguities and frequency congestion in this band, two or more satellite passes are necessary to determine if the signal is from an EPIRB and to determine the location of the EPIRB, delaying rescue by an average of 4 to 6 hours. In some cases, a rescue can be delayed as long as 12 hours.
Class A and B EPIRBs will be phased out in due course. The U.S. Coast Guard no longer recommends these EPIRBs be purchased.
Class C EPIRBs
These are manually activated devices intended for pleasure craft which do not venture far offshore and for vessels on the Great Lakes. They transmit a short burst on VHF-FM channel 16 (156.8 MHz) and a longer homing signal on channel 15 (156.75MHz). Their usefulness depends upon a coast station or another vessel guarding channel 16 and recognizing the brief, recurring tone as an EPIRB. Class C EPIRBs are not recognized outside of the United States. These EPIRBs will no longer be recognized after 1999, and are no longer recommended by the Coast Guard.
406 MHz EPIRBs
The 406 MHz EPIRB was designed to operate with satellites. The signal frequency (406 MHz) has been designated internationally for use only for distress. Other communications and interference, such as on 121.5 MHz, is not allowed on this frequency. Its signal allows a satellite local user terminal to accurately locate the EPIRB (much more accurately -- 2 to 5 km vice 25 km -- than 121.5/243 MHz devices), and identify the vessel (the signal is encoded with the vessel's identity) anywhere in the world (there is no range limitation). These devices are detectable not only by CUSPS-SARSAT satellites which are polar orbiting, but also by geostationary GOES weather satellites. EPIRBs detected by the GEOSTAR system, consisting of GOES and other geostationary satellites, send rescue authorities an instant alert, but without location information unless the EPIRB is equipped with an integral GPS receiver. EPIRBs detected by CUSPS-SARSAT (e.g. TIROS N) satellites provide rescue authorities location of distress, but location and sometimes alerting may be delayed as much as an hour or two. These EPIRBs also include a 121.5 MHZ homing signal, allowing aircraft and rescue craft to quickly find the vessel in distress. These are the only type of EPIRB which must be certified by Coast Guard approved independent laboratories before they can be sold in the United States.
A new type of 406 MHz EPIRB, having an integral GPS navigation receiver, became available in 1998. This EPIRB will send accurate location as well as identification information to rescue authorities immediately upon activation through both geostationary (GEOSTAR) and polar orbiting satellites. These types of EPIRB are the best you can buy.
GEOSTAR is scheduled to be "switched on" internationally in October 98. Although the world will not be fully covered by geostationary satellites on that date, every CUSPS-SARSAT mission control center will be able to accept and distribute GEOSTAR EPIRB alert data. The U.S. plans to maintain two EPIRB-capable GOES satellites at 75 and 135 W. Longitude. West India has two geostationary satellites (INSAT) that cover the Indian ocean and Asia. EUMETSAT (French) plan to launch a geostationary satellite that will overlap with GOES to the East and INSAT to the West. Russia is planning to launch LUCH which will overlap with GOES to the West and INSAT to the East. This will provide worldwide coverage (70 N to 70 S) similar to that provided by Inmarsat. Although the U.S. operates the GOES satellite system, it currently cannot receive EPIRB distress alert directly. The U.S. still relies on Canada for receiving EPIRB distress alerts over GOES-9, and relies on Canada, Chile, UK and Spain for receiving alerts over GOES-8.
The Coast Guard recommends you purchase a 406 MHZ EPIRB, preferably one with an integral GPS navigation receiver. A Cat I EPIRB should be purchased if it can be installed properly.
The Coast Guard urges those owning EPIRBs to periodically examine them for water tightness, battery expiration date and signal presence. FCC rules allow Class A, B, and S EPIRBs to be turned on briefly (for three audio sweeps, or one second only) during the first five minutes of each hour. Signal presence can be detected by an FM radio tuned to 99.5 MHZ, or an AM radio tuned to any vacant frequency and located close to an EPIRB. FCC rules allow Class C EPIRBs to be tested within the first five minutes of every hour, for not more than five seconds. Class C EPIRBs can be detected by a marine radio tuned to channel 15 or 16. 406 MHZ EPIRBs can be tested through its self-test function, which is an integral part of the device. Testing a 406 MHZ EPIRB by allowing it to radiate is illegal.