Also important to remember is that when you push the 911 button on SPOT, it goes to THEIR rescue center which in turns contacts a local Search and Rescue. This is not a global SAR as the Cospas-Sarsat system is.
The main problem with SPOT, well, the coverage can be spotty. Sending a message is not 100% 100% of the time. And like somebody else said, hope you remembered to change the batteries.
EPIRBs and PLBs rely on 406 MHz technology, which is much stronger than what SPOT uses. 406 will penetrate tree cover and other obstacles where GPS is known to fail. If your PLB is GPS enabled, when you activate the beacon, the GPS is sent with the 406 MHz, reducing the search area to about 100 meters. The PLB also uses the 121 homing frequency, for the "final" close search. Direction finding equipment is used, and most local SAR have this. This is the same technology used on Man Overboard products, such as the Sea Marshall.
Sea Marshall is good if you have the whole unit...the piece you take with you and the DF. Somebody on the boat has to know how to use it.
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Ok, I admit. I work for a manufactuer of PLBs and EPIRBs. I do not represent the company in any way other than to make their graphics look cool at trade shows.
But.. you can still be impressed. 
The main problem with SPOT, well, the coverage can be spotty. Sending a message is not 100% 100% of the time. And like somebody else said, hope you remembered to change the batteries.
EPIRBs and PLBs rely on 406 MHz technology, which is much stronger than what SPOT uses. 406 will penetrate tree cover and other obstacles where GPS is known to fail. If your PLB is GPS enabled, when you activate the beacon, the GPS is sent with the 406 MHz, reducing the search area to about 100 meters. The PLB also uses the 121 homing frequency, for the "final" close search. Direction finding equipment is used, and most local SAR have this. This is the same technology used on Man Overboard products, such as the Sea Marshall.
Sea Marshall is good if you have the whole unit...the piece you take with you and the DF. Somebody on the boat has to know how to use it.
*********
Ok, I admit. I work for a manufactuer of PLBs and EPIRBs. I do not represent the company in any way other than to make their graphics look cool at trade shows.

