jotron Tron 40GPS MkII, User Manual

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1.2.1 SIGNAL DETECTION
See figure 7.1.a
When the Tron 40S MkII is activated (manually or automatically) it transmits
on the frequencies 121.5 MHz and 406.037 MHz. An analogue signal is emitted
on 121.5 MHz and a digital signal is transmitted on 406.037 MHz. After the Tron
40S MkII is activated, the next passing satellite will detect the transmitted signal
and relay it to an antenna at a ground station, called an LUT.
For the 121.5 MHz signal the satellite must be within line of sight of both the Tron
40S MkII and a ground station. The ground station or LUT has a 2500 km satel-
lite reception radius centred at the LUT. In areas without LUT coverage (mostly
less populated areas in the southern hemisphere), signals from the 121.5 MHz
transmitter will not be detected by the satellites, only by passing aircraft’s. This
is not the case with the 406 MHz transmitter, because the satellites have a
memory unit, which stores the signals for relay to the next available LUT giving
it a truly global coverage.
Once the signal is received by the LUT, it is processed for location and sent
to a Mission Control Centre (MCC). The MCC sorts the alert data according to
geographic search and rescue regions and distributes the information to the
appropriate Rescue Co-ordination Centre (RCC), or if outside the national se-
arch and rescue area, to the appropriate MCC that covers the area where the
distress signal was detected. The RCC in turn takes the necessary action to ini-
tiate search and rescue activities.
The International Cospas-Sarsat System will cease satellite processing of
121.5/243 MHz beacons from 1 February 2009. From that date only 406 MHz
beacons will be detected by the Cospas-Sarsat satellite system. This affects
all maritime beacons (EPIRBs), all aviation beacons (ELTs) and all personal
beacons (PLBs)
1.2.2 DISTRESS LOCATION DETERMINATION
See figure 7.1.b
The location of the distress signal is determined by taking measurements of the
doppler shift of the EPIRB frequency when the satellite first approach and then
pass the EPIRB.
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