TX RX Systems Inc. Manual 7-9322-5 08/09/06 Page 12
mance in the presence of RF noise. Spectrum
analysis is included to determine if potentially
harmful signals are being delivered to the station
receivers. These tests are absolutely necessary,
not only to insure proper performance, but also to
serve as a bench mark for future evaluations and
troubleshooting. The post installation steps include
the following:
•
Installed sensitivity test.
•
Test port sensitivity with dummy load.
•
Test port sensitivity with antenna.
•
Spectrum analysis.
Installed Sensitivity Test
Important:
The installed sensitivity test should be
performed before the tower box connectors are
waterproofed so that they can be readily loosened
and reconnected. Taping and waterproofing fol-
lows successful completion of the post installation
tests.
The assistance of the tower climber is required
after the installation to perform the installed sensi-
tivity test. Instruct the climber to temporarily con-
nect the test cable to the antenna port. Temporarily
disconnect the test cable from the rear of the MCA
and connect it to the output of your signal genera-
tor. The correct connections are shown in
Figure
9.
Be sure that the signal generator is set up for 3
KHz deviation with a 1000 Hz tone.
•
Record the Installed sensitivity as measured.
CALCULATE CABLE LOSS
The signal loss of the test cable can be calculated
based on knowledge of the static and installed sen-
sitivities previously measured. The relationship is:
Test cable loss (dB) = Static Sensitivity (dBm) -
Installed sensitivity (dBm)
For example, if the Static Sensitivity = -126 dBm
and the Installed Sensitivity = -119 dBm then:
Test
Port
12 dB SINAD
Signal Generator
RX
MCA
RF
Out
FRX MHz
3 KHz dev
1 KHz
System fully installed
Main and base gain set
Test cable temporarily connected to
antenna port and Signal Generator
Installed sensitivity determined
- Pre-installed sensitivity = line loss
Daughter
Board
Input
Test Cable
Sampler
Port
Output
Preselector
Input
Switch
Output
Switch
Main
Test
Ant
Figure 9:
TTA system and test equipment interconnection for the installed sensitivity test.
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