NORMARC NM 7000 Series, Installation & Commissioning Handbook, Page: 118 / 189

7.7 Antenna distribution unit (ADU) phase and amplitude check
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7.7.1 Preparation
Utilise a vector voltmeter in a test set-up Figure 7-4
.
Figure 7-4 Test set-up for ADU Phase and Amplitude check.
Connect CSB and SBO outputs from Cabinet to dummy loads. Terminate the disconnected
cables from ADU to dummy loads.
Switch off the modulation to the transmitter used for the test.
Insert a 20 dB attenuator at the input port of the directional coupler.
Connect a test cable from the Cabinet’s CSB BNC connector to the 20 dB attenuator.
Connect the vector voltmeter A-probe to the directional coupler’s forward O/P.
7.7.2 Procedure
1. Connect the cable TEST SIG (throughput from the directional coupler) to the ADU SBO I/P.
Connect the B-probe to L O/P. Note the B-probe RF level (dB). (0.1 dB resolution)
Move the B-probe to U O/P. If necessary adjust phaser PH1 (AMPLITUDE ADJ) to obtain
0.0 dB difference referenced to L O/P.
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2. Connect the cable TEST SIG to the SBO input. Connect the B-probe to L O/P. Adjust the
20dB
A B
VECTOR VOLTMETER
From cabinet
CSB BNC o/p
50Ω
ADU
SBO
CSB
U
L
DIR. COUPL.