You can learn a lot more about how PLBs operate here:
I'll wait here while you go read ...
... Done already? Here's a quick summary:
- PLB tests or "I'm OK" messages sent through 406link.com, send one short signal burst, to preserve battery life.
- PLB emergency activations send a signal continuously, until the single-use battery dies, specified as a minimum of 24 hours.
- PLB locations are determined by both GPS coordinates sent with the signal, and by satellite ranging from your emergency signal even if you don't send a GPS fix. Satellite ranging can take a while, depending on satellite locations at the time of activation.
All this means:
- A successful PLB test signal received by 406link.com means everything is working. Hooray! Put your PLB away and stop worrying.
- Failure of a PLB test signal to be received by 406link.com, or with no position, or with a poor position, means almost nothing: your burst could have been sent when a satellite wasn't visible, a bird could have flown by and blocked your burst, the Internet link to 406link.com might be down, you didn't have a good GPS fix when you pushed the button, ...
If PLBs had a high failure rate in actual emergencies, we would read about many more dead people found clutching their PLBs with dead batteries. Worldwide - not just in USAF/USCG territory.
406link.com is run by the same people who are glad to sell you a new PLB after you've run your battery down repeatedly sending messages through 406link.com and a few don't go through. Think about it.