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Betting it All on EPIRBs

This article appears courtesy of the US Coast Guard. USCG Officer Jim Krezenski, the author, wrote it as a primer on the use of EPIRBs.

EPIRBs are technological marvels—provided you know when to activate them, their range, and their maintenence schedule.
Today, we're going to focus on the nautical equivalent of life insurance. Most everyone has some type of life insurance—each month pay is deducted from your check in preparation for your demise. I submit that the policy you pay for is not life insurance at all, but rather "death insurance," since this kind of investment isn't anything that will benefit you while you're alive. Real life insurance is preventative in nature, and for sailors it's derived from the money you spend on items like VHF radios, liferafts, first-aid equipment, navigation equipment, and probably the most important safety device for offshore and coastal sailors, the EPIRB.

An EPIRB, or Emergency Positioning Indicating Radio Beacon is a small battery-powered transmitting device that is carried on board, used only in case of emergency, and usually only as a last resort when your marine radio is inoperable or you are out of range. At last count, 11,471 persons have been rescued using the network of satellites these devices rely upon. Who knows, you could be next.

There are several types of EPIRBs, and the specifics vary from model to model. If a disaster strikes, some float free and automatically activate; others must be activated manually. All EPIRBs float and will send out a continual signal for 48 hours. Since EPIRB signals are primarily detected by a network of international satellites that pass overhead, occasionally there may be a delay in detection, perhaps up to an hour, because there is no satellite currently in the area to pick up the signal and relay it to shore-side rescue bases.

COSPAS-SARSAT is the international satellite-based search and rescue system established by the US, Russia, Canada, and France and makes up the backbone of maritime rescues around the world. This network locates emergency radio beacons transmitting on the frequencies 121.5, 243 and 406 Mhz. Once activated, the EPIRB should be left on to make sure the signal is available for detection by the satellite and for purposes of homing in on your location. Many models of EPIRBs also have a high-intensity strobe light to aid rescuers in locating stricken mariners once they get within visual range.

121.5 MHz Class B EPIRBs are the least expensive, but also offer reduced satellite coverage, which  is about the last thing you want in a true emergency at sea.

121.5 MHz    Class B EPIRBs that operate on 121.5/243 MHz are the least expensive, and the least capable. These were designed in the 1970s to alert aircraft flying overhead. This type of EPIRB is not well suited for satellite detection because of the problem of distinguishing them from other signals on the same frequency. Often, multiple passes of the satellites are required to identify the signal, which can further delay the rescue. And these frequencies are not stored by the satellites, therefore it is possible to find yourself in "dead zones" where no one may hear the signal. This effectively limits the 121.5 MHz EPIRBs to coastal use. These units also have a finite lifespan—the 121.5 MHz EPIRB is due to be phased out February in 2009.

All 121.5 MHz EPIRBs, often referred to as category B or mini Bs, are manual-activation units. Although these units do work with the low-earth orbiting satellite system, they do not work as well as 406 MHz beacons, and they can not be detected by the geostationary satellites that provide instantaneous alerting for 85 percent of the globe. Furthermore, 121.5 MHz beacons account for a large amount of the wasted efforts by search and rescue forces. Most 406 MHz false alerts can be resolved easily with a phone call, and in contrast, every 121.5 MHz false alert must be tracked to the source using direction-finding equipment—a costly waste of resources for already over-taxed search and rescue organizations.

"It's very important that you mount Category I EPIRBs outside the cabin where they will be able to float free of the sinking vessel."

406 Mhz    The 406 MHz EPIRBs are divided into two categories. Category I EPIRBs are activated either manually or automatically. The automatic activation is triggered when the EPIRB is released from its bracket. Category I EPIRBs are housed in a special bracket equipped with a hydrostatic release. This mechanism releases the EPIRB at a water depth of three-to-10 feet. The bouyant EPIRB then floats to the surface and begins transmitting. If you own a Category I EPIRB, it's very important that you mount it outside your vessel's cabin where it will be able to float free of the sinking vessel. Category II EPIRBs are manual activation only units. If you own one of these, it should be stored in the most accessible location on board where it can be quickly accessed in an emergency.

For offshore sailors, the 406 EPIRBS are the only common sense choice. The major advantage of the 406 MHz low-earth-orbit system is the provision of global coverage using a limited number of polar-orbiting satellite. Coverage is not continuous, however, and it again may take up to a couple of hours for an EPIRB alert to be received.

While the 406 Mhz signal frequency has been designated internationally for use only for distress, these units also include a 121.5 Mhz signal that is used mainly for homing. The signal emitted is capable of being picked up by aircraft, which may be 100 miles or more away, and by satellites orbiting more than 500 miles above the earth. While these units are more expensive, imagine yourself floating in a liferaft in the middle of the ocean, and the issue of price will likely become moot. Response time to the 406 EPIRB is dramatically reduced and the position information it provides is much more accurate.

The sea can break any vessel, so whether your aboard a cockleshell or a supertanker, the right emergency equipment is imperative for the safety of yourself and your crew.
Additionally, the 406 EPIRB's signals are coded, allowing non-EPIRB signals to be filtered out. They also provide other valuable information, which will help the search and rescue efforts. At the time of purchase you can register your EPIRB and part of the coded signal will include your name, address, phone number, vessel description, and an emergency contact shoreside who will know of your plans and capabilities. Once the satellite picks up the signal and transmits it back, the search and rescue team knows where you are and who you are.

The good frequency stability of the 406 MHz EPIRB's signal leads to a doppler estimation of the EPIRB's position between one and 50 miles.  Satellites store the EPIRB's position and transmit that information when it flies over a satellite reciever. This eliminates dead zones giving the 406 MHz EPIRB global coverage.

406 EPIRBs are carried on all US-flagged merchant vessels and are also required on commercial fishing vessels operating beyond three miles from shore. EPIRBs are also required to be licensed by the Federal Communications Commission. They should be listed on your ship's station license. Although EPIRBs are not required on recreational vessels, the USCG strongly recommends them and strongly suggests that the choice be the Category I, 406 MHz model. Its long-reaching, long-lasting signal can make a significant difference in the speed and effectiveness of rescue efforts.

The idea behind successful voyaging is to be prepared for all eventualities. Here's hoping you won't ever have to activate your EPIRB.
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 (GEOSAR) and polar-orbiting satellites. These types of EPIRB are the best you can buy, offering both reduced response time and ensuring that rescuers can monitor your position.

In a recent test of the 406 MHz model, a Naval Academy midshipman found out how effective it was. The test signal was identified within four minutes and pinpointed within 15 minutes. If that is not enough to convince you, the comparison chart below may help you make up your mind whether or not you want to "bet your life" to save a little money.

Category I, 406 MHz model

Category II, 121.5/243 MHz model

Global detection - Regional satellite
earth station not needed

Regional earth station needed - not
available in many ocean areas.
Potential for detection by overflying

Reliable beacon with low false alarms
and high probability of detection.

Beacons often incompatible with satellites.
Designed for detection by aircraft. High
number of false alarms is typical.

Beacon signal coding and exclusive
international use of the 406 MHz
frequency band for distress beacons
assures a signal received is from an
EPIRB - no problem with false alerts
from non-beacon sources

High false alert rate due to alerts
generated by other transmitters within
the 121.5 MHz

1.5 nautical mile accuracy and a
second signal provided to use for

10-20 nautical miles accuracy. Search
and rescue forces can home on the
primary signal.

Beacon is coded with owners name,
address, phone, vessel type etc.

No way to know whether signal is from
an EPIRB, similar aviation beacon, or
non-beacon source. No coded information
with signal.

Good ambiguity resolution, i.e. can
promptly launch rescue unit to a
known position with an alert from
a single satellite pass.

Hard to know which of two separate
positions calculated with first satellite pass
is the beacon location. Usually must wait
for a second satellite pass to resolve.

Putting it to the Test

A EPIRB needs periodic testing to ensure that the unit will work when called upon. Most units have a test option, but the tester should be aware that this tests the entire system—and can be the source of false alarms that can be easily prevented. The test switch activates a microprocessor on board that fires up the transmitter, oscillator, formulates a test signal, sets off the strobe light and finally broadcasts a live test transmission.

The microprocessor checks to see that all the operational elements test positive and then it gives confirming beeps and flashes. The microprocessor will not give off the appropriate confirming beep or flash if any element fails to perform and the user should take the beacon to an authorized service station for evaluation.

Operational transmission testing of a Class A or B EPIRB may only be legally executed during the first five minutes of every hour and only for three tone or one operational transmission second. During the first five minutes of every hour you can verify that your EPIRB is actually transmitting by turning it "on" near an FM radio tuned to 99.5 MHz. Placing the EPIRB a few inches from the FM radio will allow it to receive the signal and broadcast the familiar "warble" through its speakers if the EPIRB is transmitting properly. Conduct this test only during the first five minutes of each hour as indicated above.

All the lifesaving gadgets in the world won't help if they aren't properly maintained. Proper registration of your 406 MHz satellite emergency position-indicating radio beacon (EPIRB) is intended to save your life, and is mandated by Federal Communications Commission regulations. The Coast Guard is enforcing this FCC registration rule. If the EPIRB is properly registered, the Coast Guard will be able to use the registration information to immediately begin action on the case. If the EPIRB is unregistered, a distress alert may take as much as two hours longer to reach the Coast Guard over the international satellite system. If an unregistered EPIRB transmission is abbreviated for any reason, the satellite will be unable to determine the EPIRB's location, and the Coast Guard will be unable to respond to the distress alert. Unregistered EPIRBs have needlessly cost the lives of several mariners since the satellite system became operational. It's also easy. Registration can be mailed, or faxed in. For an online form, click here



Suggested Reading:

ACR RapidFix 406 by Mark Matthews

EPIRB Fundamentals by Jim Sexton

Preparing an Abandon Ship Bag by Sue and Larry


Buying Guide: Liferafts

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