It's my mistake.

I typed what I remembered from reading an earlier article, what I purchased is a PLB. Somehow I got the phrase Personal Emergency Rescue Beacon stuck in my head. So much for my memory.

Seth

I was on the SARSAT website today looking without success for formal beacon activation guidelines but did stumble across some information pertinent to beacon movement.

The SARSAT system sends regional centers one of several kinds of alerts when beacon activation is detected and continues to send them each above-horizon satellite pass until the incident is closed. Of interest:

- one message gives a satellite fix but states that the beacon ID information is not understood (for 406 Mhz). Even if they can't tell what or who you are the message is forwarded.

- the good position fix messages do tell the regional center if a satellite fixed the position or if the beacon supplied GPS data.

- if a satellite passes over a site and a signal was expected but not received the system sends an expected / not received message which regional centers receive.

- any position fix that differs from any previous position fix by more than 30 miles is specially flagged. I'm not sure what clears this flag: it seemed that any good fix by satellite or GPS would clear this.

There's nothing at the national Control Center about “two exact same location fixes”. SARSAT isn't that accurate: I think they get the GPS info tenths of an minute resolution, a few hundred feet at best (this is why ARC didn't bother to get ResQFIX's GPS accuracy better – there appears to be no way to send additional resolution even if they have it).

A consideration is that in many cases the estimated position will “move” thousands of feet at first. If a satellite position fix is made right away it will be sent through the system as a satellite fix. But the GPS will take some time to get a fix – 15 or more minutes – since it's cold started, meaning that only some later satellite pass gets GPS data. Since GPS fixes are so much better than satellite fixes that next pass may be a lot better than, and move some distance from, the first fix. It's possible that a regional center might look at a first message and see that it's satellite fix but know that the beacon manufacturer/model has internal GPS, and wait for a second satellite pass to get the GPS fix before launching SAR.

But the Control Center is going to keep sending the regional center updates every satellite pass, and if a regional center keeps simply ignoring them, with reports having good position fixes, good UID uploads and no reports of false beacon activation ... that regional coordinator is probably looking for a new job if Senator Jones' stepson owned that beacon.

As for comments in earlier messages:

- 406 MHz beacons definitely aren't good enough to tell what part of the plane you're in, even with GPS. The beacon can't give that kind of precision to the satellite as far as I can tell, even if the beacon knows.

- The satellites do not ignore any signals. Even gabled 406 MHz signals are sent to the Control Center, and policy says even unknown 406 MHz signals are sent to the regional centers if there is a satellite fix. The signal does need to be repeated correctly for the satellites to lock onto it but if the beacon sends stable garbage it's not the satellite that ignores it.

- If a position fix is on water I assume the regional center – Coast Guard? – won't be shocked to see subsequent fixes drift. They've done this before.

- Turning off a PLB during an alert seems unwise. It probably looks like a false activation being deliberately cancelled.

- In a very cold environment where the rated PLB runtime is reduced I'd try to wait until dawn to activate it. My concern is that SAR might not start at night since the odds of success are low and that environment is dangerous for SAR crews too. By activating at dawn you should still have batteries running for direction finding by the time SAR gets to you. If you activate at dusk and SAR doesn't launch until dawn you may be nearly out of beacon battery by the time SAR reaches your area.

Incidentally, there is only one system for these beacons, from PLBs up to commercial airplanes and cruise ships. It even appears that in some cases beacos for Navy subs (!) are routed through the national Control Center. The beacon's uplink data does indicate what kind of beacon it is, and of course registration data is on file, but the system itself it not segmented based on user type. PLBs are the same as the big boys as far as the satellites are concerned.

Others seem to have adequately answered most of your questions. To sum it up, the FBO owner doesn't know his butt from a hole in the ground when it comes to PLBs.

The replacment life of the lithium batteries is given at a conservative 1/2 their normal life, after taking into account all normal reduction in capacity over time including a self-test at the intervals recommended by the manufacturer, still alowing for a min. 24 hours run time at either -20 or -40 C, depending upon beacon class.

Turn on your PLB as soon as you determine you need help and leave it on.