NORMARC NM 7000 Series, Инструкция по установке и пусконаладке

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5.3 Course sector width 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.
5.3.1 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 and clearance transmitter is switched off.
For each course sector width (CS) of the array a set of corresponding DDM values exists
unique for each antenna O/P.
For CS = 4°:
For other CS values use the formula:
Example
A3 DDM for CS = 3.5°:
PROCEDURE
Turn off the clearance transmitter. Insert the 90°-stub into the course SBO path.
Connect a directional coupler with 50
Ω
load to antenna O/P A3.
% DDM
µ
A % SDM
A3 -33.7 -326 40.0
A4 -24.9 -241 40.0
A5 -17.9 -173 40.0
DDM
2 SBO
⋅
CSB
-------------------COS
γ
=
DDM
A n
( )
DDM
4
° ( )
4
° ⋅
CS
---------------------------------
=
DM
A3
( )
33.7 4
⋅
–
3.5
---------------------
38.5% = =