User's Manual

Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures
DT835A, Rev. 1 5-12
(1159965). Adjust R9 for 100% on the
Side A Power Meter.
Side B Forward Power Calibration.
In (A6) the Metering Control Panel,
located in the UHF Exciter Cabinet, find
the (A8) Dual Peak Detector Board
(1159965). Adjust R9 for 100% on the
Side B Power Meter.
5.6 Calibration of the Side A and Side
B Amplifier Arrays Reflected Output
Level
Monitor the Side A Power Meter, in the
Forward Power position, and turn the
power adjust pot, located on the (A4)
Phase/Gain Tray, to 20%. Move the
cable connected to J3, located on the
(A8) Output Coupler, inside the Side A
Amplifier Cabinet, to Jack J6 and the
cable on J6 to J3. Adjust R10 on (A9)
the Dual Peak Detector Board, located in
the Metering Control Panel, for a 20%
reading in the Reflected Power position.
At this 20% reference power reading, the
VSWR LED mounted on the front panel of
the Exciter Tray should be illuminated. If
the VSWR LED is not illuminated, adjust
R5 on (A18) the Detector Threshold
Board, located in the Metering Control
Panel, until the LED just begins to turn
on. Turn the power adjust pot slightly
CCW and the LED should go out. Turn the
pot CW until the LED just begins to turn
on. The reflected output power for the
amplifier array is now calibrated. Move
the cable connected to J6 back to J3 and
the cable on J3 back to J6, on the (A8)
Coupler.
Monitor the Side B Power Meter, in the
Forward Power position, and turn the
power adjust pot, located on the (A5)
Phase/Gain Tray for Side B, to 20%.
Move the cable connected to J3, located
on the (A8) Output Coupler, inside the
Side B Amplifier Cabinet, to Jack J6 and
the cable on J6 to J3. Adjust R10 on the
(A8) Dual Peak Detector Board, located
in the Metering Control Panel, for a 20%
reading in the Reflected Power position.
At this 20% reference power reading, the
VSWR LED mounted on the front panel of
the Exciter Tray should be illuminated. If
the VSWR LED is not illuminated, adjust
R12 on (A18) the Detector Threshold
Board, located in the Metering Control
Panel, until the LED just begins to turn
on. Turn the power adjust pot slightly
CCW and the LED should go out. Turn the
pot CW until the LED just begins to turn
on. The reflected output power for Side B
is now calibrated. Move the cable
connected to J6 back to J3 and the cable
on J3 back to J6, on the (A8) Coupler.
5.7 Phase and Gain Adjustment
Procedure for entire Amplifier Array
Assembly
Begin the alignment with all Amplifier
Trays up and running. Monitor the Reject
Power by setting the Combined Metering
switch to the Reject position and
adjusting the Phase Control on either, or
both, of the Phase/Gain Modules to
minimize the Reject reading.
Adjust the Amplifier Gain controls so that
all amplifiers have equal output power.
The Gain control on the Phase/Gain Tray
can be used to balance the output power
between Sides A and B. This adjustment
has a 10% range. If the end of its' range
is reached, you must adjust the gain of
each amplifier in the Amplifier Side to
balance the power of each Side.
5.8 Calibration of the Forward
Output Power Level of the
Transmitter
Note: - Perform the following only if the
power calibration is suspect.
Set the Transmitter up for the
appropriate Average Output Power Level.
Using a calibrated coupler on the
combined RF output line and an HP
power meter (or an equivalent