NORMARC NM 7000 Series, Installation & Commissioning Handbook

Page: 123 / 189

the monitor return cable (M1) from the lower antenna.
Adjust SBO phaser in the Cabinet (associated with Tx to air) to obtain 0 DDM reading.
Repeat the phasing procedure for the second transmitter.
Remove the 90°-stub from the SBO path.
8.4 Sector width adjustment
8.4.1 SBO power adjustment
Connect the Field Test Set to the monitor return cable (M1) from the lower antenna.
Adjust the SBO step attenuator in the cabinet (associated with Tx to air) to obtain the pre-
scribed DDM value.
For a perfect flat terrain the DDM in A1 (M1) should be -11.7%.
NOTE. To compensate for a sloping terrain in front of the GP the DDM accordingly should be:
where
θ
is the glide path angle
FSL is forward slope, negative for falling terrain referred from the GP.
Repeat the SBO attenuator adjustment for the second transmitter.
8.5 Monitor combining unit (MCU) MOA 338D adjustments
Monitor Combining Unit MOA338D is equipped with plug-in attenuators dependent upon for-
ward slope, according to the following table (AT6 is common for all FSL):
Make sure that correct attenuators are installed for the actual site.
FSL
rel.to
θ
0
Equiv.FSL
in degrees for
θ
0
= 3
°
AT3
Type AT4
Type AT5
Type AT7
Type
-0.2
θ
0
±
0.05
θ
0
-0.6
° ±
0.15
°
AT1305B AT1305G AT1305
M AT1305S
-0.1
θ
0
±
0.05
θ
0
-0.3
° ±
0.15
°
AT1305C AT1305H AT1305N AT1305T
0.0
θ
0
±
0.05
θ
0
0.0
° ±
0.15
°
AT1305D AT1305J AT1305P AT1305U
+0.1
θ
0
±
0.05
θ
0
+0.3
° ±
0.15
°
AT1305E AT1305K AT1305Q AT1305V
+0.2
θ
0
±
0.05
θ
0
+0.6
° ±
0.15
°
AT1305F AT1305L AT1305B AT1305
W
DDM
11.7
θ
0
FSL –
( )
–
θ
0
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=