Elt/epirb

[poncho]

Can Anybody tell me the difference between an ELT and EPIRB.

Poncho

[Islander Jock]

I often wondered the same question myself until I was doing some research recently on another issue in relation to SARSAT and came accross this in the following document found at the COSPAS SARSAT website:

GUIDELINES
FOR PARTICIPATING IN THE
COSPAS-SARSAT SYSTEM
April 2000
Issue 3



2.2 Practical Aspects of The Use of The Cospas-Sarsat System
Distress beacons for use with the Cospas-Sarsat System operate at 406 MHz and/or
121.5 MHz. They are referred to as:
- Emergency Position Indicating Radio Beacons (EPIRBs) when designed for use
on vessels;
- Emergency Locator Transmitters (ELTs) when designed for use on aircraft; and
- Personal Locator Beacons (PLBs) when designed for use by individuals.

So referring to an aircraft or personal pocket beacon as an EPIRB would be incorrect according to the honchos who own the satellites.

[Desert Duck]

EPIRB and ELT have a slightly different tone.

[Islander Jock]

G'day DD,

I wondered if this was the case also on the assumption that the RCCs would want to know upon receipt of a distress beacon if they are dealing with an aircraft or vessel. However, the COSPAS document on technical characterics does not really specifiy whether EPIRBS or ELTs have been coded differently but I did find the following:

5.2 SPECIFICATION FOR THE 121.5 MHZ COMPONENT OF EMERGENCY LOCATOR TRANSMITTER (ELT) FOR SEARCH AND RESCUE
Note.- Some ELTs are equipped with an optional voice capability (A3E) in addition to the
A3X emission.
5.2.1.5 The carrier shall be amplitude modulated at a modulation factor of at least 0.85.
5.2.1.6 The modulation applied to the carrier shall have a minimum duty cycle of
33 per cent.
5.2.1.7 The emission shall have a distinctive audio characteristic achieved by amplitude modulating the carrier with an audio frequency sweeping downward over a range of not less
than 700 Hz within the range 1 600 Hz to 300 Hz and with a sweep repetition rate of between 2 Hz and 4 Hz.

TECHNICAL CHARACTERISTICS OF EMERGENCY POSITION-INDICATING RADIO BEACONS (EPIRBs) OPERATING ON THE CARRIER FREQUENCIES OF 121.5 MHz AND 243 MHz
EPIRBs operating on the carrier frequencies of 121.5 MHz and 243 MHz should fulfil the following conditions (see Note 1):

c) the emission should consist of a characteristic audio-frequency signal obtained by amplitude modulation of the carrier frequencies with a downward audio-frequency sweep
within a range of not less than 700 between 1 600 Hz and 300 Hz and with a sweep repetition rate of two to four times per second;
d) the emission should include a clearly defined carrier frequency distinct from the modulation sideband components; in particular, at least 30% of the power should be contained at all times within:
F 30 Hz of the carrier frequency on 121.5 MHz;
F 60 Hz of the carrier frequency on 243 MHz;

NOTE 1 - Additional characteristics for EPIRBs aboard aircraft are specified in the relevant
annexes to the Convention on International Civil Aviation.

I have deleted the irrelevant parts of reference before posting here.
The emission, audio frequency sweep and repetition appears the same for both EPIRBs and ELTs.
I have had a pretty good look again through the COSPAS / SARSAT handbook and cannot find any reference to different signal coding and EPIRB or ELT.

Perhaps not all ELTs / EPIRBs monitoring tones are a reflection of the signal pattern being transmitted.

A quick phone call to AUSSAR should be able to clear this one up.

The 406MHz system is of course anther matter which will be capable of transmitting all sorts of pertinent data, including GPS coordinates.