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WARNING: Disconnect and lockout AC primary power prior to servicing
60
2.17.3.5 Three and Four Cabinet Calibration
Using the tables below calibrate the reject loads. Data is in cabinet power percentages.
CABINET CABINET CABINET A/B AB/C COMBINED
A B C REJECT REJECT OUTPUT
100 0 0 50 16.6 33.3
0 100 0 50 16.6 33.3
0 0 100 0 66.6 33.3
100 100 0 0 66.6 133.3
100 0 100 50 16.6 133.3
100 100 100 0 0 300
Figure 2-3 Three Cabinets
CABINETS A/B CABINETS C/D AB/CD COMBINED
A & B REJECT C & D REJECT REJECT OUTPUT
ONE 50 BOTH 0 25 225
BOTH 0 ONE 50 25 225
BOTH 0 NONE 0 100 100
ONE 50 ONE 50 0 100
BOTH 0 BOTH 0 0 400
Figure 2-4 Four Cabinets
2.18 Visual VSWR Calibration
VSWR calibration follows forward and reflected power calibration. The VSWR
foldback will limit the reflected power to a fixed value.
The VSWR foldback will limit the reflected power to a fixed value, the 1.22:1 value is
1% of the normal forward power. An example is a 2 cabinet PA that has a normal
forward power of 6.2 KW. The foldback will limit the reflected power to 62 Watts. The
second line of protection is the module internal VSWR protection. Modules will always
VSWR protect using the module logic.
IF you have confidence in the power calibration, you can let the software use the default
values of 1.22:1 as the foldback fault point and 1.40:1 for VSWR fault. Other values can be
entered from the Output tab, service screen. If you want to verify operation, substitute a
variable level RF source for the reflected sample such the output of the back-up exciter and
increase the level to check the foldback point.
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