Installation Instructions

Table Of Contents

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1.3.1 DDM check of ADU O/P (output port)

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.

For CS = 5°:

For other CS values use the formula:

Example

A3 DDM for CS = 5.4°:

PROCEDURE

Insert the 90°-stub into the SBO path.

Connect a directional coupler with 50* load to antenna O/P A3.

Connect the NM3710 (use 20 dB attenuator at NM3710 I/P) to the directional coupler's for-

ward port.

Adjust the SBO attenuator (for the Tx to air) until the DDM value equals the previously calcu-

lated value for the CS.

%DDM µA %SDM

A2 -34.8 -337 40.0

A3 -32.7 -316 40.0

DDM

2 SBO⋅

CSB

-------------------

COSγ=

DDM

An()

DDM

5°()

5°⋅

---------------------------------

32.7 5⋅–

5.4

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29.5%==