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PLB w GPS time delay

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Jan 4, 2010
983
Farr 30 San Francisco
So I am thinking of getting a PLB with integrated GPS, I am interested in the ACR 375+ model.
This is a 406MHZ model with integrated GPS. So in principle it broadcasts your exact location. So rescue odds are improved

However, reading the manual it seems that this isn't quite so. Looks like your GPS location is broadcast or updated only every half hour. This is done I bet to save battery.
If you read some of ACR's online survivors stories there was one where the coasties flew right past the guys in the water waving the flares to a nearby location and then found the guys in the water waving the flares after executing a small search pattern..

Am I confused? wrong on the facts? Is there a PLB that updates GPS more often perhaps in an adaptive way?

Where I sail I could in principle sink at the Golden Gate bridge at max tide and be miles away from the broadcast position by the time rescue arrived at my old position.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
These type of devices are not intended to replace your VHF radio. They are intended for open ocean sailing away from land. Your point is well taken though. Go down crossing the gulf stream and you could be miles away from the last updated position. Course in 1/2 hour the USCG will have a better idea AND be on site. I suspect you should plan to be there at least several hours (I'd plan for days but that is me). don't see this as a problem
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
There are two broadcasts going on with this device.

The PLB will signal the satellite via 406MHz and send your GPS fix within minutes, then it updates that fix every 30 minutes via 406MHz. At the same time the device is broadcasting a constant locator signal on 121MHz.

So: Stay fixed, stay with your boat if possible. Once rescue reaches your vicinity they will switch to 121MHz and home in on you.

Hope that helps.
 
Oct 2, 2006
1,517
Jboat J24 commack
I did safety at sea 2012 and the rescue module was done by a CG pilot

ALL there fast rescues are done with a VHF equipped victim as there is a whole lot of square feet once they get in the general area
 
Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
John, position is extrapolated. If after the first broadcast of your GPS coordinates, a second broadcast is received, then the difference in time, location, and speed will dictate where you could be on the next broadcast. Kind of like leading the target if I may.

I would think that in the story of the guys between Catalina and Long Beach, the helo found them but move some distance away for safety. On all video that I have seen of rescues, the helo was never over the victims until they were lifted aboard. Keeps the prop wash off of them. Have you ever been hit by the prop wash of a UH60 or CH46? I can tell you it hurts. :) The part about moving forward is my opinion. The part about the prop wash is fact.
 
Jan 4, 2010
983
Farr 30 San Francisco
Well I have a friend in the Civil Air Patrol, he explained that they have in addition to a 121mhz DF gear 406MHz DF gear and will home on that signal which is a 5W burst. The flew right past them thing is expected, vision straight ahead is poor. Unless somebody is hanging out vision down is also poor.

The sobering thing is he said "I wouldn't want to be in a position where I was relying on this system for rescue"

Dead men tell no tales, so we don't hear about cases where the system doesn't work. He is a bit on the cautious/paranoid side.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Consider the difference between an incapacitated hiker requiring rescue in a brush and forested location, and a sailor floating in an expanse of open water. The CAP faces a much more formidable challenge in their land-based rescue mission than the USCG does with their marine based mission. Which isn't to minimize the CG proficiency, these guys are rock star rescue trained pros. You stay with your boat, practice your signaling protocols and you have a very high chance of rescue.
 
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