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Subject: RE: [worldcruising] 406 EPIRB???
From: Rick Kennerly (nh2f@XXX.XXX)
Date: Fri Feb 22 2002 - 10:03:46 EST
Oh, if you're getting an EPIRB I'd go for the 406 GPS GPIRB unit and not
look back. If you get the straight 406 unit, then the satellites have to
triangulate your position (through a kind of dopler shift analysis), which
gives SAR your location within smaller area than with 121.5, but it's still
a pretty large area. Depending on satellite coverage in your area, it may
also take some time for the satellites to "refine" your position. However,
the 406 GPS GPIRB unit will, on the very first contact, broadcast your ID
number and your GPS coordinates within yards, all within 5 minutes. This is
particularly important if you've got a bum battery (or very cold water) that
may not keep the unit operating long enough for a really refined 406 only
position.
121.5 EPRIBS are old technology and being phased out. But 121.5 still a
satellite based system and the triangulation process is similar to working
with straight 406 EPIRB, but 121.5 EPIRBs do not pass the encoded
information about your ship to SAR (actually 406 EPIRBs broadcast a
registration number and then SAR looks up the information about you and your
boat).
However, all 406 EPIRBs are also 121.5 transmitters--they transmit on both
freqs. That's because SAR will use the 121.5 signal for their close-in
direction finding, once they get into the general area.
You may not have a chance to use your VHF if, for instance, you're rundown,
dismasted, suffer a propane explosion, or are afire. Then it's nice to go
over the side with a GPIRB.
Rick
----------------------------------------------------------
Rick the Mouseherder - nh2f
Westsail 32 Xapic, Hull #438
Cabo San Juan, Puerto Rico
A small boat and a suitcase full of money
beats a 40 footer tied to the Bank.
Visit our Westsail 32 Xapic
http://www.mouseherder.com/xapic
The Westsail Owners Assn. Homepage
http://www.westsail.org
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