Features December 2003 Issue

Personal Locator Beacons

Personal locator beacons, or PLBs, provide the benefits of 406 MHz distress signaling, but at a more affordable price. And unlike an EPIRB, they’re small enough to attach to a life jacket.

]by Doug Ritter

The advantages of 406 MHz distress alerting over 121.5 MHz are significant and they are a proven lifesaver. The 121.5 MHz EPIRB is being aggressively phased out. Satellite alerting from 121.5 MHz EPIRBs will end in 2009, but the Coast Guard is trying to hurry things along even quicker. The CG has proposed to the FCC that certification of new class A, B and S (121.5 MHz) EPIRBs cease, and that by the end of 2006 the operation of these 121.5 EPIRBs cease; in other words, be declared illegal. 


With the price of 406 MHz EPIRBs having dropped a great deal in recent years, and their proven superiority as an alerting and locating beacon, we can see little reason to keep a 121.5 MHz EPIRB aboard.

But 406 MHz EPIRBs do carry a big drawback—they're too large and too bulky to strap on a PFD. Moreover, EPIRBs just aren't very practical for smaller boats or dinghies. ACR has offered a pocket-sized EPIRB—the ACR MiniB family—for some time, but these units have all the operational disadvantages of any 121.5 EPIRB.

In other parts of the world, a more compact 406 MHz beacon has been available for personal use. These devices are called Personal Locator Beacons, or PLBs. After years of opposition from the FAA, the U.S. Air Force and others, which prevented the sale of PLBs in the U.S., these valuable safety devices are now available in the United States. This article introduces you to the products on the market.

What They Are
The PLB is a pocket-sized, manually operated, emergency beacon providing essentially the same alerting capabilities as a 406 MHz EPIRB for prices that are coming within reach for people who believe in maximum personal security. Street prices for the most basic ACR model are now under $500.

These PLBs are compact enough to carry easily on your person, and most manufacturers provide a pouch that can be attached to your PFD. Look for PFD manufacturers to include built-in pouches as PLBs catch on.

The larger ones weigh about a pound; the smallest are about half that weight and not much larger than a cigarette pack. As with most electronics, there is an inverse relationship between cost and size; smaller is more expensive, at least at this juncture. Because the PLB is small and portable, a sailor could take it on other adventures (hiking, for instance) and further justify its expense.

The U.S. added requirements to the international PLB standards. They must include a 25-milliwatt 121.5 analog homing signal, not required by COSPAS-SARSAT standards. While less powerful than an EPIRB's 121.5 MHz signal, the 406 MHz primary beacon transmission provides increased accuracy, so this doesn't represent any decrease in safety or effectiveness. Inserted into the homing signal at the insistence of the FAA is a Morse code P to distinguish a PLB from an ELT (Emergency Locator Transmitter, strictly an aviation beacon) or a standard EPIRB, for that matter.

Sorting Them Out
PLBs can be categorized by various attributes, which in turn affect performance and price. The specifications delineate Class 1 and Class 2 PLBs, the former providing a minimum of 24 hours of operation at -40° C, the latter 24 hours at -20° C. For most boating purposes, a Class 2 PLB will be adequate. The improved cold-weather performance of the Class 1 has generally required a considerably larger battery, adding bulk and weight, though one manufacturer seems to have circumvented that with a higher technology battery providing 48 hours at –20°, likely equivalent to Class 1, but not yet certified to that standard.

By comparison, an EPIRB is required to transmit for 48 hours at –40° C. The difference is a major reason that allows these to become personal size, the battery being the primary driver of weight and bulk.

Category 1 PLBs are inherently buoyant. That is an obvious advantage for marine use, but a secure tether would also likely suffice (and a tether should be used in any case). The buoyant PLBs are not the smallest available, so depending upon your priorities, you might want to depend solely on a tether in exchange for smaller size. It's important to note that the buoyant PLBs will not float upright in the transmitting position, like an EPIRB, but they also won't sink.

For someone floating in a PFD, the PLB will need to be held or secured on top of the vest with the antenna pointed skyward and out of the water for the most part. Some PLBs have adjustable antennas; others are fixed. With an inflatable PFD, some of the PLBs can be wedged between the inflated chambers. Those thinking ahead may want to secure some Velcro on the PFD and the PLB to make this easier.

We'll make a predication that it's only a matter of time before some bright entrepreneur gets together with a beacon manufacturer and develops a PFD with an integrated PLB and a remote antenna attached strategically to the PFD that deploys automatically. All the wearer will need to do is switch it on.

And that's an important point. PLBs are manually activated— they can't be activated by a water-sensing switch. So you must be conscious to activate one, which limits the PLB's usefulness as an MOB device. The manual activation requirement was driven by a desire to cut down on false and inadvertent alerts that plague the system. Perhaps the future will bring a solution, once the authorities become comfortable with the technology.

The most significant performance difference among the beacons relates to actual location and notification performance. Self-locating beacons use GPS to transmit your location almost instantaneously to the geostationary satellites, which for the most part cover from 70° North to 70° South latitudes. There is no need to wait until a Low Earth Orbiting satellite passes overhead to produce a location via Doppler computations. The location accuracy is also much better—on the order of less than a 300-foot radius, versus about a three-mile radius from 406 MHz locating alone, worst case. That's the theory at least. Actual results can vary quite a bit depending upon how well the GPS works and other circumstances.

Self-locating PLBs may accept GPS coordinates from an external GPS, or they may have their own integrated GPS chip and antenna. The former is less expensive; the latter is a more compact solution, though you will pay a premium for the capability.

GPS is not a panacea and has limitations. Self-locating beacons must be operated optimally for GPS to work to its best advantage, or even at all. As with any GPS receiver, it requires a clear sky and a reasonably stable antenna pointed skyward. Too much motion, as in heavy seas, will defeat the very basic antennas included in either the integrated beacons or most handheld GPS receivers, preventing the GPS from receiving enough satellites to determine an accurate location. All are "fail-safe," in the sense that they will not transmit an unreliable location. In any case, the 5-watt 406 MHz distress signal will still punch through and provide location accuracy of less than a three-mile radius, and experience suggests it is often far better.

Current PLBs use lithium-based batteries (meeting DOT requirements) with a minimum five-year replacement interval, though actual service life may be longer.

As with 406 MHz EPIRBs, PLBs must be registered, for free, with NOAA. For online registration go to: www.beaconregistration.noaa.gov (for PLBs and EPIRBs). This will also allow inputting of a float plan that is immediately provided to Search and Rescue in case of an alert. The chart includes those PLBs currently COSPAS-SARSAT-certified and expected to be available in the U.S.

Prices are fluctuating, but at press time, www.onlinemarine.com was selling the ACR 406 PLB without GPS for $498, and the unit with GPS for $589. The Pains Wessex FastFind PLB, with GPS, is on sale for $899 at www.consumersmarine.com.


Also With This Article
CLick here to view "Specs: Personal Locator Beacons."
CLick here to view "Personal EPIRBs?"

• ACR Electronics, 954/981-3333, www.acrelectronics.com
• Revere Supply, (McMurdo Pains-Wessex), 973/575-8811, www.reveresupply.com
• SERPE-IESM (Kannad), 011 33 (0) 2 97 02 49 49, www.serpe-iesm.com
• Wireless Concepts Inc., 805/582-9000, www.wireless-concepts.com

-Contributing editor Doug Ritter is an expert in safety matters. He runs the non-profit Equipped to Survive Foundation. See www.equipped.org.

Comments (0)

Be the first to comment on this post using the section below.

New to Practical Sailor?
Register for Free!

Already Registered?
Log In