Installation Manual Part 6

FCC ID: CDG-ARTU EXHIBIT C
MAGNASTAR C-2000 DIGITAL AIRBORNE TELEPHONE SYSTEM
9.1.7 ARTU RECEIVE SIGNAL STRENGTH MEASUREMENT
The ARTU Receive Signal Strength measurement test will verify the complete RF portion of the C-2000
system. This test will require the use of a MagnaStar Loop-Around test box. During this test a 16 QAM
signal is transmitted by the ARTU. With the MagnaStar Loop-Around test box connected to the Antenna,
the signal is coupled into the Loop-Around test box where it is mixed by 45 MHz and coupled back into the
Antenna. A receive signal strength measurement using the ARTU checks out both the TSC and Pilot
receive channels of the ARTU as well all the components between the ARTU and the Antenna. The
frequency of the transmitted signal is 894.9495 MHz.
This test is to check for gross loss problems in the RF cables and associated hardware and is not intended to
be a calibrated test measurement. Typically the value should be measured at - 103 dBm +/- 6 dB with
nominally valued components. Because the TSC and Pilot channels are separate receivers, variations
between measurements are possible. If, however, there is a delta between the two receivers of greater than
10 dB, the ARTU is to be rejected.
The Loop-Around test box is powered by a 9 volt battery. The battery voltage must be greater than 6.0
volts to operate and provide the expected perfonnance results. The Loop-Around test box provides the
capability to check the battery to ensure that the voltage is correct. The Loop-Around test box attenuator
setting should be set to the "ON" position for the first part of this test. Switching the attenuator to the
"OFF" position should change the receive signal strength by approximately 30 dB.
Symptom: Reading between the TXRX and RX receivers greater than 10 dB.
If the delta between the TXRX (TSC) and RX (Pilot) receivers is greatertban 10 dB, repeat the
test. If after repeating the test the same results occur then replace the ARTU.
Symptom: RSS readings on both the TXRX and RX channels less than -109 dBm (-103 dBm - 6 dB)
If the RSS readings are less than -109 dBm then the lossy component needs to be located. If the
ARTU Transmitter Output Power test has been successfully completed then the problem is either
the Antenna, Duplexer, Receive cable or ARTU. If the ARTU has successfully passed BIT, then
the most likely candidates are the Antenna, Duplexer or the receive cable. With the proper
adapters, cable loss should be measured for the ARTU receive cable. Elimination of the receive
cable as the problem leaves the Duplexer and Antenna. With the proper adapters and a 30 dB/25
Watt pad, the antenna cable can be directly attached to the Loop-Around test box bypassing the
Antenna. If the loss problem still exists after bypassing the Antenna, replace the Duplexer.
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: This test step i8 instructional only. :
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: In preparation for measuring the syst.. receive 8ignal strength. the :
: loop around test box -.t be configured and properly placed for expected :
: results. Perfora a battery check prior to use by turning .ON. the loop :
: around test box and pressing the -.ntary battery check _itch. 'ft1e :
: indicator light vill illU8inate if the battary is within operational :
: require8eDts. set the attenuator svitch to the .ON. position. Place the :
: cable clip-on cla.p on the center of the blade antenna for best results. :
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Figure 9. 7 A. ARTU Receive Signal Strength Measurement MMTI Troubleshoot Screen.
' V4.0A MMT Radio Responses
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