Custom Search

This evaluation tested both EPIRBs and PLBs. Both transmit a 5 Watt digital burst of approximately 0.5 seconds duration approximately every 50 seconds. This period is randomly distributed between 47.5 to 52.5 seconds to prevent multiple beacon transmissions from interfering with each other. Both transmit an equivalent digital message. However, there are notable differences between the two types of beacons. EPIRBs are meant to be carried on and deployed from a marine vessel; PLBs are meant to be carried by a person and deployed by an individual in distress. EPIRBs are intended to be used only in a marine environment; PLBs may be used on land or in a marine environment, but are only tested during certification in a land environment. As such, with the exception of the baseline tests, EPIRBs were tested only in the marine environment.

EPIRBs come in both automatically deployed or manually deployed models. Category I EPIRBs are activated either manually or automatically. Category I EPIRBs are housed in a bracket equipped with a hydrostatic release that releases the EPIRB when the vessel sinks. The EPIRB is activated when released and floats to the surface. An EPIRB thus released will float free unless retrieved by survivors in the water or in a survival craft. Category II EPIRBs are manual activation only units. Both categories of EPIRBs are designed to activate when they are immersed in water, regardless of the position of the manual switch.

EPIRBs must float with the antenna deployed and out of the water in the normal transmitting position. U.S. regulation requires that they be equipped with a strobe light that activates automatically when the beacon is switched on. All have a means to tether the EPIRB to a vessel or survival craft so they will float free while secured to the survival craft. They must operate for at least 48 hours at either -40°C to +55°C (Class 1) or -20°C to +55°C (Class 2). COSPAS-SARSAT standards assume that the body of water in which the EPIRB is floating will serve as the ground plane for the antenna.

PLBs are generally smaller because they require smaller batteries, being required to operate for only 24 hours at either -40°C to +55°C (Class 1) or -20°C to +55°C (Class 2). They are not required to be equipped with a strobe light. All are currently equipped with a tether of some sort, although this may just be a wrist tether. Category 1 PLBs must be buoyant; Category 2 PLBs are not buoyant. Category 1 PLBs are not required to float in a transmitting position—they simply are required not to sink, the objective being solely to help prevent loss if dropped into the water. Howevr, they are not precluded from floating in a transmitting position. PLBs are manually activated only.

It has been noted that in real survival situations many EPIRBs are retrieved from the water after automatic release and activation or are retrieved from the vessel by survivors when they abandon ship into a life raft. In either case the EPIRB is then retained inside the life raft, rather than being floated in the water on the end of their very thin tether line, as designed. In some cases this appears to be the result of ignorance as to how to deploy the EPIRB as designed. In other situations, it appears that as their primary hope for rescue, survivors do not appear to be willing to trust their life to that thin tether, particularly in severe conditions. In a number of documented cases, the tether line was not securely tied off to the life raft and was separated from the life raft. Since they will tend to drift at different rates, they can quickly become separated. At least one life raft manufacturer, in recognition of this, provides an option for a secure pocket in the life raft to hold the EPIRB. (NOTE: Some aviation life rafts come equipped with an ELT (aviation version of an emergency beacon) that is secured semi-permanently in the raft, and some also activate the ELT automatically upon deployment of the raft.) In recognition of this reality, we tested EPIRBs both floating tethered to a vessel and retained inside a life raft.

PLBs were tested on land, held by persons floating in the water (or simulation of same) and in the life raft.

Message from Scuba Steve:
Be sure to visit to make your purchase.