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The Workings of a 406 MHz Personal Locator Beacon

written by: Daniel P. McGoldrick•edited by: Michele McDonough•updated: 6/9/2009

This article in our series about Personal Locator Beacons with GPS remote tracking capabilities explains how a 406 MHz PLB works in conjunction with GPS satellite technology and the built in homing beacon. How successful at saving lives is this complex system?

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    The Technology Behind 406 MHz PLBs

    When a 406 Mhz PLB with a GPS Beacon is engaged by pressing the button on the device, the GPS receiver in the hand held device is turned on and it acquires your coordinates by using GPS satellites. Once it has your precise location, the powerful 406 Mhz signal on the PLB sends those coordinates through deep canopied forests or foul weather of any variety up into the atmosphere where a second set of satellites dedicated solely to search and rescue pick it up. The LEOSAR (Low Earth Orbit Search And Rescue) rovers out there in space can locate your position using a phenomenon known as Doppler Shift (remember though this is redundant in many PLB models because that 406 MHz signal is already emitting your GPS signal).

    The second fail safe eye in the sky is the GEOSAR (Geosynchronous Search and Rescue System). These are far out in space orbiting at 22,000 miles from the earth. They have a huge view of whatever quadrant of the earth they’re fixated on and have the ability to pick up a beacon signal pretty much instantaneously. Both of these satellite systems that pick up your alert signal then relay it back to Local User Terminals (LUTS) on earth. The LUTS then sends the data to the appropriate Mission Control Center. Every beacon has a unique signature when activated. When you buy a beacon you register it online with your personal information so the MCC knows exactly who you are.

    The MCC relays your position to the Rescue Coordination Center (RCC) which then coordinates with the local rescue agency to initiate whatever means they have at their disposal to go out and get you out of trouble. That may seem like many links in a chain but the whole process works amazingly quick, especially when you consider the global scope of this process and all those bureaucracies. The RCC also calls your family or whoever you put down as an emergency contact when you registered your beacon.

    Once the rescue operation is out there looking for you they track you down by using the homing signal, which is also on your PLB device, which broadcasts on most models at 121.5 MHz. As you can see, these devices have a series of redundant capabilities to ensure the maximum potential for saving the lives of the persons who use them. This satellite tracking system has been responsible for saving the lives of over 350 people in at least 130 reported incidents in the U.S. alone in recent years.

The 406 MHZ PLB Explained and Reviews of The Best Models

In this informative series you will learn what a Persolonal Locator Beacon with GPS is, how they work in conjunction with satellites and rescue authorities, and what features make the best device model. Also included are reviews of two ACR PLBs; the Terrafix 406 GPS PLB and the Resqfix 406.
  1. The 406 MHz Personal Locator Beacon
  2. The Workings of a 406 MHz Personal Locator Beacon
  3. A Review of the ACR TerraFix 406 GPS I/O PLB with GPS
  4. ACR ResQFix 406 Personal Locator Beacon (PLB) with GPS – 2897 Review