I viewed with scepticism the Rodale's release of Palau Aggressor's planned EPRIB
distribution to buddy teams.
While I have only several hundred hours underwater, I have several thousand on the
water, mostly offshore.
I'm fairly abreast of EPIRBs, past and present.

Someone already posted that there are modern ones (406 MHz) and older, simpler ones
(121/243 MHz).
All are designed to be picked up by satellite, relayed to a center, where the info
is deployed to search and rescue.
The 406 Mhz ones are picked up by geosynchronous orbiting satellites, can pinpoint
the source to within a mile, and are can be interfaced with GPSes to radio exact
location.    All have registration numbers, so the owner of the emergency beacon is
known when it goes off.   They also have a 121 MHz homing beacon for the end game of
search and rescue.

The 121/243 MHz systems have been plagued by false alarms, and there is a plan to
phase out coverage of them.   They are covered by low earth satellites only, not the
better geosynchronous ones.   At the moment, Soviet satellites will quit in 2006, US
in 2009, but there is discussion about speeding that up, like the GPS selective
availability speed up.   At the moment they are almost always ignored for days, as
there are so many triggered by kids turning them on,  boaters "testing" them,
etc.      If they keep running for 24 hours, someone might investigate.

Every offshore mariner knows the 406 Mhz system is the required one for coast guard
equipment, and the one of choice for those wanting to be rescued should the need
arise.   No serious boater buys the 121 Mhz system.

Recently,  a variant of this system, together with a radio direction finder (RDF),
have started to show up in marine catalogs as "personal locators".   The notion is
the mother ship will use the RDF to find the beeping locator.    It would appear to
be a shifting of the technology to another use, as it's obsolete for offshore search
and rescue.    Labeled "coastal", to keep people from buying then as offshore gear,
they are listed in catalogs.   At the moment they are not for sale in the US, since
opposition to those systems is fierce at the search and rescue level..

My skepticism about them centers on the use of the 121 Mhz system,  since it will
also trigger  every low earth SAR satellite as it passes overhead,  exacerbating the
current problem.   It's also  line of site system, so will have limited use at
sea.    The RDF is designed to be hand held, so will remain at bridge height.  On my
boat that would limit useful range to about 8 miles.

As far as making it sealed to 200 feet, that's not a big challenge.   Keeping it
sealed with months of beating about on a dive deck is another issue.
I expect it will have a tendency to suffer maintenance issues with time, both in
battery life, severe shocks (drops) and case cracking.
The are not easy to test, as that is the same as a "emergency", and the satellites
all pick it up.    If fact, they are sort of like bullets.   You never know if
they're going to fire until you need it to.

As for Palau, if the mother ship is moored up at German Channel and the dive is off
Blue Corner, it's unlikely the captain can see the beacon with the RDF.  Not only is
it out of range (curve of the earth) it's behind the islands, which blocks it.    If
I could only carry a strobe/safety sausage or one of the EPRIBs, my own choice would
clearly be the strobe/sausage.    Most divers are not bluewater seamen, and the
EPIRB seems more like advertising to
attract them than an actual safety enhancement.

By the way, it's not on the Aggressor site at the moment, but I might call them just
to hear the spiel.


Wade