Measure and record in Ground Commissioning Record the return loss value for each LPDA
including antenna cable.
Tolerance: 20 dB minimum.
Figure 2-3 Antenna return loss measurement set-up.
2.3
Course sector adjustment
The required course sector width (CS) can be pre-adjusted by two methods:
1. DDM measurement of ADU antenna feed outputs.
2. DDM field check.
Preferably both methods should be carried out and compared.
2.3.1
DDM check of ADU O/P
At each antenna feed output of the ADU the measured DDM is a result of the SBO/CSB ratio
according to the formula
where
CSB is a fixed value.
SBO is adjustable by the SBO attenuator in the cabinet.
γ
is 0° when the 90°-stub is inserted into the SBO.
For each course sector width (CS) of the array a set of corresponding DDM values exists
unique for each antenna O/P.
20dB
A
B
VECTOR VOLTMETER
From cabinet
CSB BNC o/p
DIR. COUPL.
Antenna cable under test
Antenna
DMM
2 SBO
⋅
CSB
-------------------COS
γ
=
Summary of Contents for NM 7000 Series
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