Ideally, you want an EPIRB or PLB that transmits on both frequencies; ACR and McMurdo are the two major sources. If you only go offshore occasionally and don't want to spend the money to purchase an EPIRB, BoatUS (www.boatus.com) rents them for an incredibly reasonable fee and will deliver one to your door prior to your departure!
Why 406 MHz?
The U.S. Coast Guard changed from 121.5 to 406 EPIRB frequencies because:
? Responding to the tremendous number of 121.5 MHz false alerts (most of which originate from non-beacon sources) relayed by satellites is not efficient and needlessly expends limited resources or diverts resources from real incidents. (There was an average of 120,000 false alerts per year over the past three years in the United States alone.)
? The signal from 121.5 MHz doesn't carry vessel-identification information, meaning SAR must actually launch rescue resources to resolve the incident or determine that it's false.
? The 406 MHz system, designed for relay through satellites, is operational and provides increased reliability, identification information, better location accuracy, a global capability and quicker alerting through the geostationary satellite system.
EPIRBs and PLBs
Category 1 EPIRBs attach directly to your boat, self-deploy from a bracket and automatically activate if submerged (generally at around three to 15 feet). They can also be manually deployed, and lest you worry about the signal traveling through water, all float to the surface once free of the bracket.