User's Manual

Table Of Contents
Test Set Calibration68P64115A18–1
Mar 2003
1X SC 4812T Lite BTS Optimization/ATP Software Release R2.16.1.x
DRAFT
3-77
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:
1. 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
short cable is deducted from the measured loss of the TX and RX
test cable configurations to determine the actual loss of the
configurations. This deduction is done so any error in the analyzer
measurement will be adjusted out of both the TX and RX
measurements.
2. 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 and, if required by BTS type, an additional
attenuator are also required for the RX test cable configuration.
These additional items must be included in the path loss
measurement.
3. 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 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.