User's Manual

Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures
DT835A, Rev. 1 5-11
Amplifier Tray for 50% output
power and adjust the Phase control
to mid range.
4. Monitor the output power of the
Transmitter by connecting a
Spectrum Analyzer to the Sample
Jack located on the Metering Panel.
Adjust the Spectrum Analyzer for
Zero Span operation. The power
could be monitored by watching the
meters on the panel but the power
change is easier to see on the
analyzer.
5. Turn On the AC to Amplifier Tray #2
and adjust its' output power to
50%.
6. While monitoring the output power
of the Transmitter, adjust the Phase
Control on amplifier tray #2 until
the power reaches a peak. If the
Phase adjust reaches its end of
travel, add a 2 inch cable to the RF
Input (J1) of amplifier tray #2. Re-
adjust the Phase to peak the
System output power. If the Phase
Control again reaches its end of
travel before a peak in power is
reached, remove the 2 inch cable
and add a 3 inch cable to J1 of
amplifier tray #2 and readjust
phase for peak output power. The
adding of cables should be done
during the adjustment anytime the
range of the phase adjust needs
extended.
7. Repeat steps 5 and 6 for the
remaining Amplifiers.
8. Increase the output power on
Amplifier #1 and Amplifier #2 to
90%.
9. Adjust the Phase Control on
Amplifier #2 to peak the System
output power.
10. Increase the output power on
Amplifier #3 to 90% and adjust the
Amplifier #3 Phase control for
maximum System output power.
11. Increase the output power on
Amplifier #4 to 90% and adjust the
Amplifier #4 Phase control for
maximum System output power.
12. Increase the output power on
Amplifier #5, if present, to 90%
and adjust the Amplifier #5 Phase
control for maximum System output
power.
13. Increase the output power on
Amplifier #6, if present, to 90%
and adjust the Amplifier #6 Phase
control for maximum System output
power.
14. Monitor the Reflected Power on all
of the UHF Amplifier Trays. The
Reflected Power should read <5%.
If an amplifier is showing high
reflected power adjust the Phase
control to minimize Reflected
Power. Be careful not to increase
Reflected Power on the other
Amplifier Trays. The Amplifier
Trays should interact in such a way
that the phasing of any one
Amplifier will affect the Reflected on
the other Amplifiers.
5.5 Calibration of the Side A and Side
B Amplifier Arrays Forward Output
Power Level
Note: Perform the following
procedure only if the power
calibration is suspect.
Set up the transmitter for the appropriate
average output power level out of the
Side A Cabinet. A calibrated coupler and
average power wattmeter must be used
to measure the digital power level.
Side A Forward Power Calibration.
In (A6) the Metering Control Panel,
located in the UHF Exciter Cabinet, find
the (A9) Dual Peak Detector Board