5
TESTING PROCEDURE EXPLAINED
The 406 Mhz. emergency beacon system, unlike the previous simple system, has
many features designed to enhance reliability and reduce search times. As such,
it sends a more complicated signal and is therefore important that all aspects of
its signal are tested and verified. There are 2 basic types of tests, RF power
output from the beacon (power meter), and the amount of power being radiated
from the antenna (field strength) and permitting both should be accomplished.
The POWER METER mode of testing is an off the air test and requires at least 3
transmissions from the beacon
to complete. This is an actual operational test of
the beacon that checks all aspects of the signal it is sending. This method is only
possible on beacons that use an external antenna giving direct access to the
transmitter typically aviation ELTs, and some marine beacons
The other is an on the air test, FIELD STRENGTH, of the beacon and uses the test
mode function required for all beacons. The test function is identified as such to
the COSPAS SARSAT system so that it will not trigger a search, but as such not all
aspects of the beacon are tested. Instead of measuring the power output of the
beacon, this test measures the strength of the RF field the beacon and its antenna
are producing. This is a product of not only the amount of power generated by
the beacon but also the efficiency of the antenna system.
Unless you want to initiate a search, DO NOT OPERATIONALLY ACTIVATE A
BEACON WHILE CONNECTED TO AN ANTENNA. After the second transmission, it
will set off an alarm and start a search. The Creative Electronics tester includes an
ANTENNA LOAD to replace the beacon antenna when testing the beacon and is
also used in the POWER METER mode to measure the actual power the beacon is
producing. When running this test, the beacon should be placed in a RF shielded
container to prevent accidental radiation of a signal that the system could
receive, since a plastic enclosure will not shield the signal and the cables used to
connect the tester to the beacon need to be double shielded cables.
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