EPIRB Frequency Guide for Sailors
An EPIRB operates primarily at the 406 MHz frequency band, which is monitored by the COSPAS-SARSAT satellite system and is detectable by satellites globally.
The comprehensive coverage and range of this technology ensures that distress signals can be transmitted from anywhere in the world.
A secondary frequency, 121.5/243 MHz, acts as a homing signal for local search and rescue operations, although it’s less common since it is not satellite-monitored.
- Primary frequency: 406 MHz
- Secondary frequencies: 121.5/243 MHz
Signal Structure
The signal sent from an EPIRB includes a unique identifier and a data burst containing crucial information.
This structure is capable of being detected by both COSPAS-SARSAT satellites and in some cases by GOES weather satellites.
The standard alarm signal is an AM signal, with characteristics designed specifically for satellite detection and interference avoidance:
Modulation | Tone sweep |
---|---|
Amplitude modulated (AM) signal | 1600 Hz to 300 Hz, 2-4 sweeps |
GPS Integration
Modern EPIRBs are often equipped with GPS, enhancing the accuracy of the distress signal’s location data.
Once an EPIRB is activated, it transmits GPS coordinates along with the distress signal to the 406 MHz satellite network, greatly improving response times.
The result is faster pinpointing of your location for the search and rescue team from the transmitted GPS coordinates.
Types of EPIRBs
As you know by now EPIRBs use a frequency signal of 406 MHz. A Personal Locator Beacon (PLB) can be thought of as a type of EPIRB and also operates on the same frequency.
I’ve detailed the difference between EPIRBs and PLBs to teach you the ins and outs of both. But here’s a quick recap.
Registering your EPIRB is paramount and links your device to crucial contact information, which is vital in emergencies. You should register your EPIRB with your national authority, ensuring that all details are up-to-date.
If you own a private boat, you’re not exempt from compliance. Although not always mandatory, equipping your vessel with an EPIRB that meets performance standards and ensuring its registration enhances your safety at sea.
Alert and Distress Signal Processing
Once activated, your distress signal is captured by satellite systems, decoded, and relayed to search and rescue authorities who initiate the proper response to locate and assist you.
Reception by Satellites and Ground Stations
The distress signal transmitted by your EPIRB is received by two principal satellite systems: GEOSAR (Geostationary Search and Rescue) and LEOSAR (Low-Earth Orbit Search and Rescue).
The powerful LEOSAR satellites utilize the Doppler shift in signals to determine your beacon’s position with increased accuracy.
For immediate and continuous coverage, the GEOSAR satellites provide a persistent watch but without the Doppler positioning advantage.
After satellite reception, signals are directed to Local User Terminals (LUTs), which process the information and forward it to the appropriate Rescue Coordination Centre (RCC).
GEOSAR | Provides continuous coverage; no Doppler information |
LEOSAR | Calculates position using Doppler shift; intermittent coverage |
Doppler Shift | This effect is used by LEOSAR to improve location accuracy |
LUTs | Ground stations that receive your distress signal from satellites |
Relay to Search and Rescue Authorities
On receiving your distress signal, the rescue co-ordination center (RCC) initiates the deployment of search and rescue resources.
They utilize tracking equipment and, if your EPIRB is equipped with AIS (Automatic Identification System) signals to pinpoint your location.
The 406 MHz frequency is key for enabling effective global coverage and swift response times.
The National Oceanic and Atmospheric Administration (NOAA) in collaboration with INMARSAT E enhances the overall efficiency of distress alerting.
Your EPIRB’s signal integrity and quick processing are essential in effectively conveying your emergency.
RCC | A hub that coordinates search and rescue efforts upon receiving the signal |
AIS | An additional communication layer that can improve localization |
NOAA & INMARSAT E | Agencies and systems that work to ensure fast and accurate signal relay to rescuers |
Distress Alerting | The process whereby your emergency signal is identified and acted upon |