INTERESTING PLB STORY

[HMT2]

Last Thursday I got a call from United States Air Force rescue services. I initially thought I was getting a solicitation on my cell phone. Great… then the sergeant asked me if I owned personal locator beacon number XYZ ABC, that got my attention. I said yes I own a PLB and I fortunately had the unique number of my PLB in my cell phone. I asked the sergeant if there was a problem, he replied yes your PLB has activated somewhere in the Yucatán. We matched the numbers to what he said was broadcasting and the numbers of my properly registered PLB. Having just seen my boat two days prior I knew she could not physically be in the Yucatán so I told the sergeant that I had not laid my eyes on at the beacon in several months because it resides in my nav table and I don’t pull it out every time I go to the boat. I finished my tasks at work and went immediately to my boat. I was not surprised (perhaps a bit relieved) to see her in her slip. I opened my nav table and there sat my PLB unopened and not broadcasting. I called the sergeant from the United States Air Force and told him that I had at the beacon in my hand and had no evidence of it broadcasting anything. He checked the incoming distress call and saw that it had only flashed the one time; it did not send another distress call or location. The Sergeant then told me this happens every now and then but not to worry that when/if you need your beacon it will work.… I hope he is right. Anyone else ever hear of such a thing?

 

[Sailm8]

I am wondering why would the ID number be incorrect? Does it take multiple "fixes" to get it right? Hmmm

 

[HMT2]

I am wondering why would the ID number be incorrect? Does it take multiple "fixes" to get it right? Hmmm

The number he showed transmitting was the same as my PLB, but mine never transmitted a thing.

 

[Gunni]

This is very troubling. Not sure if it is related but NOAA SARSAT has been playing around with a change to PLB SAR alerts in the CONUS. Essentially they want to turn over the SAR to local resources. But they want to keep USAF in the middle. I suspect with no particular info that in some kind of drill handshake that they could have fumbled. All this does not explain an alert to the Yucatán.

 

[rpwillia]

One thing to remember is that the PLB or even an EPIRB transmits at 406MHz and that the signal including your PLB ID, Timestamp, Latitude and Longitude are digitally encoded with error correction codes. The idea on error correction codes is that you want to have enough to detect errors but not too many that it takes longer to transmit. It is possible they received a signal, but that enough bits were garbled that the signal was improperly received and did not recover the signal correctly. Since the PLB/EPIRB does not handshake with the satellite but does a one-way transmission there is no way for the satellite to request a re-transmission if there were enough errors it could not recover the signal. On subsequent transmissions it is probable that the correct signal would be recovered. I would not lose a lot of sleep, stuff happens. FWIW, in 2005 I helped develop a plan to update COSPAS-SARSAT at NOAA; it is a pretty good system.

 

[HMT2]

It is possible they received a signal, but that enough bits were garbled

The PLB was in my nav table inside my boat and had literally been untouched by human hands. The antenna was not extended or open. So how could/would it broadcast anything?

 

[rpwillia]

I am thinking it was not your PLB, but more likely someone with an ID close to yours. Could have been an accidental transmission as there was only one.

 

[CarlN]

This isn't at all surprising. The COSPAS-SARSAT system is 35 years old and technologically obsolete. It was designed pre-GPS, pre-internet, pre-SMS and pre-mobile phone. The satellites use an analog doppler system to create lines of position.. Accuracy is very low by today's standards and subject to numerous forms of atmospheric interference. Fortunately, GPS is now supported too but it is used only to improve the doppler fix. Worse, the system is run by an alphabet soup of dozens of government agencies with no one really in charge and improvements are almost impossible. It's remarkable that it still basically works.

Virtually all EPIRB activations occur while the vessel is still afloat. And virtually all are close enough to SAR or other vessels to be reached within six hours. It would be even quicker except 95% of activations are errors so SAR delays launching a rescue to make telephone (!) calls to contacts in the database. The database doesn't allow you to put in SMS or email addresses. Of course, the person called doesn't know what's going on either. As happened here.

I now carry a InReach as my primary beacon. I would only go to the backup EPIRB if I didn't get a response on the InReach. And with a bi-directional system like the InReach, SAR can immediately contact the person in distress to confirm the signal and to get information on the nature of the distress (medical emergencies are the most frequent reasons for distress calls). SAR can then provide instructions on the rescue ETA and preparations. 15 years from now, I expect COSPAS-SARSAT will have followed LORAN into the history books.

 

[Head Sail]

Are you sure he was USAF? Why would they call about a Mexican incident? Whole thing sounds like a phishing scam.

 

[HMT2]

Are you sure he was USAF? Why would they call about a Mexican incident? Whole thing sounds like a phishing scam.

Not even close to a phishing scam. He had my PLB number, my cell number I used on the NOAA registration and never asked for any information of a private nature. I have no doubt the man was exactly who he said he was.

 

[Gunni]

InReach will get you your brother Butkiss, maybe. EPIRB/PLB will get you the pros with the gear and know how to bring you home.

PLBs are registered to a person and routed by USAF, EPIRB are registered to a vessel and routed by USCG.

 

[Skipper]

InReach will get you your brother Butkiss, maybe. EPIRB/PLB will get you the pros with the gear and know how to bring you home.

PLBs are registered to a person and routed by USAF, EPIRB are registered to a vessel and routed by USCG.

And InReach requires a monthly fee. A big fee.
Even the part time service is not much less.
PLB is free service forever.
If you're cheap like me, and only need sat capability for rescue, then it's fantastic.
Also, you don't have to remember to pay for your rescue service every month. Wouldn't it bite royally if you're in distress 100 miles offshore and your InReach says "No service"?