User's Manual

Test Set Calibration68P09258A31–A
Oct 2003
1X SCt 4812T BTS Optimization/ATP
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Calibrating Cables Overview
The LMF Cable Calibration function is used to measure the path loss (in
dB) for the TX and RX cables, adapters, directional couplers, and
attenuators that make up the cable configurations used for testing. A
communications system analyzer is used to measure the loss of both the
TX test cable and the RX test cable configurations. LMF cable
calibration consists of the following processes:
Measure the loss of a short cable
This is done to compensate for any measurement error of the
communications system analyzer. The short cable, which is used only for
the calibration process, is connected in series with both the TX and RX
test cable configurations when they are measured.
The measured loss of the TX and RX test cable configurations minus the
measured loss of the short cable equals the actual loss of the
configurations. This is done so that any error in the analyzer
measurement is eliminated from both the TX and RX measurements.
Measure the loss of the short cable plus the RX test
cable configuration
The RX test cable configuration normally consists only of a coax cable
with type–N connectors that is long enough to reach from the BTS RX
connector to the test equipment.
When the BTS antenna connectors carry duplexed TX and RX signals, a
directional coupler is required and an additional attenuator may also be
required (for certain BTS types) for the RX test cable configuration.
These additional items must be included in the path loss measurement.
Measure the loss of the short cable plus the TX test
cable configuration
The TX test cable configuration normally consists of two coax cables
with type–N connectors, a directional coupler, a termination load with
sufficient rating to dissipate the BTS output power, and an additional
attenuator, if required by the BTS type. The total path loss of the TX test
configuration must be as required for the BTS (normally 30 or 50 dB).
The Motorola Cybertest analyzer differs from other communications
system analyzers because the required attenuation/load is built into the
test set. Because of this, the Cybertest TX test configuration consists
only of the required length coax cable.
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