mcmurdo Fastfind, Руководство по обслуживанию

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Commercial in confidence 85-909
PLB service manual Issue 4 Page 10
GPS Test
The GPS system should be tested only when its operation is suspect.
Because of the time required to obtain a GPS position, it is necessary to operate the PLB in
the live transmission mode, and hence it must be contained in a screened enclosure for the
duration of this test. This in turn means that the GPS signal must be re-transmitted inside the
screened enclosure using a GPS repeater and internal antenna. The test may take up to 5
minutes and requires the external GPS antenna to have a view of at least 4 GPS satellites.
It is necessary to verify the content of the GPS position information transmitted by the PLB,
using a suitable message reader connected to an antenna inside the screened box.
Successful acquisition of a GPS position is indicated by the flashing green light on the PLB.
Equipment
Screened enclosure
Message reader (ARG5410 or equivalent)
GPS antenna, repeater and retransmitting antenna
Procedure
Switch on PLB and immediately place it inside the screened enclosure.
Monitor the 406 MHz transmissions displayed by the message reader until positional
information is obtained.
If the positional information has not been obtained within 5 minutes, wait until immediately
after a 406 MHz transmission and switch off the PLB. Restart the test.
GPS
antenna
Power supply
12v 300mA
Screened
enclosure
Repeater
Internal
antenna
PLB under
test
50 ohm
screened
coax cable.
15M max
50 ohm
screened coax
cable. 1M
10dB
attenuator
Message
reader