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Comparison of different types of EPIRBs:
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EPIRB
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EPIRB is an unprotected abbreviation. The abbreviation EPIRB stands for Emergency Position Indicating Radio Beacon. Therefore the incorporation of a position finding device (GPS) is mandatory. The 406-MHz-, the 1,6-GHz- and the DSC-type system definitions allow for position coding within the transmitted message. But only the Inmarsat-E-Type 1,6-GHz-EPIRBs makes use of this feature. Unfortunately, most 406-MHz-beacons lack this feature. The following tables compare features and technical data of different beacons.
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In recent time discount suppliers are misusing the term EPIRB to sell simple 121,5-MHz-beacons (PLT/ELT). The customer should be aware of cheap offers which never provide for a beacon capable of transmitting its identification. Cheap beacons (PLT/ELT) sold as "EPIRBs" never incorporate position finding devices, either.The financial benefit severely bribes the genuine security capabilities of the device.

Comparison of EPIRBs by their features :
(Click here for technical data or get an explanation of the abbreviations)
Feature
ELT / PLT
(121.5 MHz)
EPIRB
(406 MHz)
EPIRB
(1.6 GHz, Inmarsat-E)
DSC-EPIRB***
SART
permitted, recommended or optional features
none
Strobe-Light, ELT
Strobe-Light, ELT, SART
Strobe-Light, SART
Strobe-Light
Vehicle- 
Identifikation
no
yes
yes
yes
no
is received and processed by ...
COSPAS / SARSAT, planes and SAR-forces
COSPAS / SARSAT (LEO satellites)
Inmarsat, (geostationary satellites)
costal radio stations
vessels within visibility
transmission of the nature of distress
no
possible, not used
possible with RCU,
strongly recommended
possible
no
coverage
the whole world
the whole world
97% of the earth,
up to ± 80° lattitude
(excluding polecaps)
sea-area A1, only in the vincinity of the coast
-
period until valid reception
up to two hours
up to two hours
within 3-10 min **
immediately,
no delay
-
minimal mandatory time of operation
-
24 h
75 min TX within 48 h
48 h
96 h stby 
8 h TX
specifications to apply
IEC, IMO GMDSS-Handbook
IMO GMDSS-Handbook
Inmarsat SDM 2.0, 
IMO-GMDSS-Handbook 
IEC1097-5 
ETSI 300 372
IMO GMDSS-Handbook
GMDSS-Handbook

** = Inmarsat calls for a delay of 2-8 minutes after activation. Processing the signals within the LES takes about less than a minute.
*** = For the time beeing, there are no DSC-EPIRBs available on the word market.

 
Technical data of different EPIRBs :
Feature
ELT / PLT
(121.5 MHz)
EPIRB
(406 MHz)
EPIRB
(1.6 GHz, INMARSAT-E)
DSC-EPIRB
SART
position-transmission, measurement
thru SAT and/or SAR-vehicules
thru SAT
yes, own position determination
possible, 
own position determination
none ! Position determination by receiving vessel
Type of position-processing
Doppler-shift because of SAT-movement, or VHF-direction finder
Doppler-shift because of SAT-movement
GPS or navigation system of the vessel
navigation system of the vessel or GPS
none
frequencies
121,5 MHz 
(sometimes 243 MHz)
406.025 MHz
667 channels
(300 Hz spacing) at 1,645 GHz
VHF CH 70 
(156.525 MHz)
9.2 - 9.5 GHz
Type of modulation
Carrier keying 
(A1 / A1A)
PSK, NRZ
±  1.1 rad
(G1B)
FSK ± 120 Hz,
NRZ (G2B)
FSK,
300 / 2100 Hz,
h=2 (G2B)
carrier keying 
100 ms 
(A0 / A1)
Datarate (Baud)
-
400
32
1200
-
Bit per transmission
1
135
160
variable
-
Polarisation
vertical
RHCP 
RHCP 
vertical
horizontal
transmission power
no recommendations
5 W
1 W
100 mW
400 mW
temperature range
-
-20 ° to 55 °
-20 ° bis 55 °
-20 ° to 55 °
-20 ° to 55 °

 
Abbreviations :
COSPAS Cosmicheskaya Sistyema Poiska Ava riynich Sudov
(= Space System for the Search of Vessels in Distress), comparison with Inmarsat-E.
DSC Digital Selective Calling
ELT Emergency Locator Transmitter (121,5 MHz Baken-Sender)
EPIRB Emergency Position Indicating Radio Beacon (406 MHz oder 1,6 GHz Notsender)
GMDSS Global Maritime Distress and Safety System
LES Land Earth Station, Receiving Satation for Satellite-Signals (picture)
LEO Low Earth Orbit
MMSI Maritime Mobile Service Identity,
like a ships telephone number in the maritime radio, (VHF, SW und MW)
PLB Personal Locator Beacon (121,5 MHz Baken-Sender, am Körper zu tragen)
SAR Search and Rescue (Rettungsdienst)
SARSAT Search and Rescue Satellite, comparison with Inmarsat-E.
SART Search and Rescue Radar Transponder
SOLAS Safety of Life at Sea, Rules for the Equipment of ships > 300 grt
RCU Remote Control Unit, enter nature of distress and remote activate the EPIRB from the ships bridge. For a picture click here.
RHCP Right Hand Circular Polarisation
SAT Satellit
IMO International Maritime Organisation
GPS Global Positioning System (Satellitennavigationssystem)
VHF Very High Frequency