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A Better PLB Standard Approved

RTCM logoEver since the first ETS Foundation 406 MHz GPS Beacon Evaluation revealed significant shortcomings in some of the beacons I have been working to encourage improvement of the standards to which PLBs are approved and manufactured. The first stage involved tightening up the COPSAS-SARSAT standards, T.001 and T.007 that cover all 406 MHz distress beacons. Some pretty significant changes were made to ensure that the beacons are now tested in less than ideal conditions to better assure they will work satisfactorily in real world use. You can read more about that here.

The next step was to address the RTCM standard for PLBs that covers other aspects of the device, many of which touch on the human interface and usability of the PLB. The RTCM standard serves as the basis for FCC approval of the beacons for sale in the U.S. Because the U.S. is such a large market, it also becomes something of a de facto standard for the world, to some varying degrees. A special subcommittee of the SC110 committee was tasked with that job and we have been meeting for a couple years to hammer out a better standard. In April, the revised RTCM 11010.2 standard was approved. While this doesn’t address all the issues, some work still remains, it goes a long way towards implementing tougher and more stringent standards for PLBs.

The main changes that have been included in the latest version of the RTCM PLB standard are:

  • References have been updated to reflect latest updated and improved COSPAS-SARSAT standards as noted above.
  • Added Internal Navigation Device Timing requirements that front load the GPS Receiver operation (on PLBs equipped with GPS). The GPS position is allowed to be updated no more often than every 20 minutes after an initial location is transmitted in accordance with the COSPAS-SARSAT standard, so the GPS receiver in a PLB does not operate all the time. The receiver chip consumes considerable power, so it is only turned on at intervals for brief periods as necessary, considerably reducing power requirements and the size of the battery (and thus weight and size of the PLB). In the past, various manufacturers have used their own GPS timing schemes, in part because they had different views of the priority of this information and in part to maximize battery conservation.

    Search and Rescue representatives on the committee, in consultation with their respective organizations, have advised that the most critical time to get a GPS location is in the first hour. After that, a Doppler location has likely been obtained anyway and the more time passes, the less critical it is. Given a limited “power budget,” and with industry knowledge of the peculiarities of the way these GPS receivers work best, it was determined to maximize the potential for gaining a location in this critical time period.

    To summarize the new timing scheme, in the first 60 minutes the GPS will make at least 3 attempts to obtain an initial location and will be turned on for a cumulative total of no less than 30 minutes. If the GPS fails to obtain an initial location within the first 60 minutes then it will continue to make at least one attempt every 15 minutes for the next hour of operation (2 hours total time). Each attempt at obtaining an initial location will require the GPS to be powered up for a period of at least 5 minutes each time.

    Once an initial valid location (fix) has been encoded into the beacon message, or after 2 hours, the navigation device will attempt location updates following a regime set out in the standard, which starts out with at least one fix / location update every 30 minutes for the first 6 hours thereafter.

    This change ensures that the GPS is given the best opportunity to obtain a location in this critical time period when it will do the most good, plus now all beacon manufacturers will incorporate this front loaded timing scheme into their PLBs.

    Annex G in the standard has been reserved for future addition of Internal Navigation Device (GPS) Test Methods and Test Procedures. This turned out to be a tougher nut to crack than expected. While good progress has been made in developing simulator testing schemes to ensure the GPS meets a minimum standard, it’s complicated and time consuming to establish and verify the test scenarios, procedures and test scripts and adjust them as necessary to ensure an appropriate level of GPS location performance. If we waited until that was entirely sorted out, it might have delayed the standard by a year, perhaps more. Since everything else would stand on its own and the improvements are significant, the new standard was approved, with a place reserved to insert the GPS testing once it is ready. The GPS testing requirements will follow in good time, but meanwhile everyone can start building a better PLB to the new standard.

    It should be noted that no organization has ever previously set minimum requirements for GPS locating performance into a standard such as we are doing here, one reason it is taking a longer time to accomplish. We cannot simply reference some other standard or modify an existing standard. RTCM is leading the way.

  • Somewhat related to this, additionally, PLBs with GPS are now allowed and encouraged to provide for the transmission of a self-test encoded GPS derived location as part of a unique and separate GPS self-test option. In the past, it was prohibited to do so. This will allow beacon testers to record the actual location being transmitted to test the integrity of the GPS location capability.
  • Improved PLB Labeling requirements were added (location of GPS antenna and warning not to obstruct it, whether PLB floats or not, readability and intelligibility testing requirement to help ensure that any instructions are easily understood and definition of operational configuration so users understand how to best orient and deploy the PLB, and in the case of a PLB with GPS, how to maximize the opportunity to get a location).
  • Improved PLB documentation requirements (User Manual) requirements added (instructions on safe (hazardous cargos) transportation, details on connecting external GPS Receivers to the PLB and many other improvements).
  • Packaging Labeling requirements added. This standard breaks new ground in this area, for the first time requiring specific information be provided to the potential purchaser on the PLB’s consumer packaging. The buyer will now be presented with enough information, prior to purchase or opening the box, to determine if the PLB is designed and built for their particular uses. This includes plain English information on class and category and suitability for various environments as well as notes that PLB does not meet regulatory carriage requirements for an ELT or EPIRB.
  • 121.5 MHz homing beacon Off Ground Plane Radiated Power Test added. This corresponds to the new testing added in the COSPAS-SARSAT standard for the primary 406 MHz distress transmission. It helps ensure that the PLB 121.5 MHz homer will actually work under less than ideal real world conditions. The Morse Code P in the 121.5 MHz transmission for U.S. PLBs is now fully integrated into the standard, not just an addendum.
  • In addition, many other minor changes have been incorporated including tighter environmental testing requirements and others. It is a much more robust standard which will result in better PLBs. It significantly raises the bar to help provide confidence these PLBs will save your life when called upon to do so.

    The revised PLB standard will be published shortly. Once published, RTCM will formally petition the FCC to adopt the standard into the FCC Part 95 rules. The FCC will officially review it (they already participated on the committee), probably issue a pro forma NPRM, and then is expected to formally incorporate it into the U.S. regulations by reference. All this will take some time, even if done on an expedited basis. Because there are some new tests involved, it is expected that the FCC will allow manufacturers a year to meet the new rules, based on past experience, but that is entirely up to the FCC. However, it should be noted that some manufacturers are already incorporating many of these changes from the standard in new PLBs, even prior to the standard being approved or written into the regulations. The revised standard should be adopted by industry quite quickly.

    I am very pleased to have had a hand in making this happen. There is no question that without the field testing that the Foundation conducted, the issues would likely never have seen the light of day until there was some sort of tragedy. Then, by getting involved in the standard setting process, I have been able the help push and shepherd the changes needed. Many of the changes enumerated above were initially proposed in the Recommendations section of our Beacon Evaluations.

    As the sole consumer advocate participating on these standard setting committees, I have tried to focus on two goals; ensuring that these lifesaving devices are likely to function reliably in real world conditions and that the end user, the potential survivor, is equipped with the information needed to make best use of the device if needed. All this must be balanced with the need to keep the device both affordable and accessible and allow future engineers and designers freedom to innovate. Those are oftentimes conflicting goals and it is credit to the industry, government and SAR representatives who have participated that we have done what I feel is a damn fine job of balancing these requirements.

    Please support Equipped To Survive with a tax-deductible donationBring this to fruition has taken years of meetings and lots of effort. The cost of travel, lodging and the like is not insignificant, no matter how frugally done. I contribute my time to the cause, but when I am working on things like this, I am not earning a living, keeping a roof over our head. As my grandfather used to remind me, money does not grow on trees. Your contributions and purchases of Doug Ritter Gear are what make this possible. There’s plenty more work to do, not just with distress beacons (revising the EPIRB standard is next for SC110), but with other safety and survival equipment with other committees I work with. Please consider helping to support this work with a contribution.