User's Manual

Test Set Calibration – continued
3-104 1X SC 4812T Lite BTS Optimization/ATP FEB 2005
PRELIMINARY
LMF Cables Calibration
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 Signal Loss of
both the TX Test Cable and the RX Test Cable Configurations. The LMF
Cable Calibration consists of the following processes:
Measure the Signal Loss in a Short Cable
This measurement is done to compensate for any Measurement Error in
the Communications System Analyzer. The Short Test 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 Signal Loss in the Short Test Cable is deducted from the
measured Signal Loss of the TX and RX Test Cable Configurations to
determine the actual loss of the configurations. This deduction is done so
that any error in the analyzer measurement can be adjusted out of both
the TX and RX Measurements.
Measure the Signal Loss in 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. If required by BTS Type, an additional
Attenuator is also required for the RX Test Cable Configuration. These
additional items must be included in the Path Loss Measurement.
Measure the Signal Loss in 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 is
different 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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