HOME   ❯Press Release   ❯  Emergency Beacons and Radio Direction Finders Save Lives
Press Release
Emergency Beacons and Radio Direction Finders Save Lives

Price, UT - June 28, 2011 -- The life expectancy of an uninjured person involved in an aircraft accident is measured in days. An injured person or someone in cold water needs help immediately if they are going to survive. Modern technology is making it possible to find people in distress faster than ever.


Some activities like flying and boating bring with them legal requirements to carry emergency radio beacons. Some companies require it for the protection of their employees. In past years, emergency beacons transmitted on 121.5 MHz and/or 243.0 MHz. February 1, 2009 saw the end of satellite detection of the legacy radio frequencies. The COSPAS-SARSAT system no longer listens for them. All current emergency beacons transmit on one of nineteen (19) 406 MHz frequencies in the COSPAS-SARSAT frequency plan.


The following three types of beacons all transmit on a 406 MHz frequency: Emergency Locator Beacon (ELT), Emergency Position Indication Radio Beacon (EPIRB) and Personal Locator Beacon (PLB). All three are all basically the same. The big difference is their method of activation and who uses them. ELTs are impact activated and used by aircraft. EPIRBs are water activated and designed for maritime use. PLBs are meant to be carried by a person and are manually activated.


A fourth type of emergency beacon is a Maritime Survivor Locating Device (MSLD). MSLDs only transmit on 121.5 MHz. They are not intended to have the COSPAS-SARSAT satellites detect them. The goal is to have the vessel that the person fell from know immediately that a person is in distress and provide help. For an MSLD to work properly the vessel a person is from needs to have radio direction finder to give the ability to track the beacon.


Although 121.5 MHz and 243.0 MHz are no longer monitored by satellites, the frequencies have not gone away. Even new emergency beacons can have 121.5 MHz homing beacons built in. Most do. The output power of the homing beacon has been turned down; consequently, Search and Rescue personnel need to be closer to a beacon to detect it on 121.5 MHz than they would have been in pre-406 MHz beacon days.


To compensate for the lower 121.5 MHz output power, 406 MHz beacons transmit a 5 watt pulse which is considerably higher power than even the old 121.5 MHz emergency beacons. To achieve adequate battery life the 406 MHz signal is only transmitted approximately every 50 seconds. The transmit time is intentionally random to insure that if two beacons are activated at the same time they will never be synchronized and transmit at the same time all the time. It is still possible that they will have random events when they both transmit concurrently.


Some emergency beacons include built in GPS receivers or a port to receive GPS data from an external GPS. This is to feed a GPS location to COSPAS-SARSAT. This is great when it works. Remember we are not in a perfect world. Aircraft like to flip over and cover the GPS antenna. I have seen PLBs and EPIRBS put in the cabin of boats for protection by the crew or the boat capsize, either of which will effectively block the GPS antenna. I have even seen PLBs placed face down in the snow blocking the GPS signal.

COSPAS-SARSAT is a great system and has taken into account some of the problems of the real world and the GPS weaknesses. Even if the beacon doesn’t have GPS data for any reason the beacon is still transmitting a radio signal approximately once every 50 seconds and the 121.5 MHz homer is constantly transmitting. COSPAS-SARSAT can triangulate a beacon from the 406 MHz pulses and give an approximate location of the beacon.


After an approximate location is determined a radio direction finder like the RHOTHETA RT-600 / DF-517 is capable of detecting and tracking the beacon. Even the short pulse of the 406 MHz burst can be tracked.


The RT-600 / DF-517 can scan and detect all 19 COSPOS-SARSAT 406 MHz frequencies, decode the data it is transmitting and display it for SAR teams.


Depending on terrain and altitude of the RT-600, detection and tracking of the signal is possible from 90 nautical miles or greater. As you get closer to the beacon the direction finder can be tuned to 121.5 MHz to track the continues signal making it possible to locate a beacon in any weather or lighting condition. Recently New Mexico State police located a downed aircraft using a RT-600. The aircraft had impacted the side of a mountain and was not visible from the air; however, the accuracy of the direction finder took them right to the crash site.


The RT-600 / DF-517 has frequency agility giving an operator the ability to track a number of radio sources. All 88 maritime frequencies can be tracked. Using a RT-600 designed for law enforcement, agencies can track other beacons like LoJack’s theft recovery system and Electronic Tracking Systems, beacons.


Although we aviation types like to fly, weather and other factors must be considered. In addition to aviation radio direction finders, RHOTHERTA also manufactures equipment for maritime and land use.


In a perfect world emergency beacons would not be needed; however, we are not there. Aircraft go down, boats sink and people get lost in the woods. Other bad things happen to good people. An emergency beacon can save your life.


Lon B. Arnold is the President of RHOTHETA USA, Inc. He has been involved with airborne and ground emergency services for the past 30 years. He can be reached at lon.arnold@rhothetaamerica.com or by phone at 435-578-1270.

#   #   #