E.F. Johnson Company 242-20X1-213, Manual

Page: 104 / 198

ALIGNMENT AND TEST PROCEDURES
7-6
August 2000
Part No. 001-2001-200
9. Press the space bar to key the Exciter.
10.Set RV101 for "best" square wave as observed on
the modulation analyzer output to the oscilloscope.
NOTE: Ensure that the oscilloscope is "DC" coupled
and turn off de-emphasis and HPF switches on the
Modulation Analyzer.
11. Press the space bar to unkey the Exciter.
12.Repeat Steps 1-7. Very little adjustment of RV401
should be needed.
7.3 110W POWER AMPLIFIER ALIGNMENT
7.3.1 INTRODUCTION
Refer to Figures 7-3 and 7-4 for component loca-
tions. Refer to Figure 7-8 for equipment needed and
setup diagram. Select "PA" from the "TEST" menu in
the Repeater Software.
7.3.2 DRIVER TUNING AND LIMIT ADJUST-
MENTS
1. Connect an antenna or dummy load to the RF port
(50 ohm impedance).
2. Connect the:
Power supply ground lead to P105
+15V DC lead to P103
+26.5V DC lead to P101
36-pin cable to J101 on the RFIB
3. Set the signal generator to +19 dBm
±
0.1 dB.
Connect the signal generator to A9.
4. Press the space bar to key the PA.
5. Monitor the voltage on R45 on the RFIB and set
R76 for 1.3V DC (see Figure 7-4).
7.3.3 POWER AMPLIFIER TUNING
This procedure assumes that either:
•
The carrier is chosen and the coaxial cable from the
exciter is putting out +19 dBm
OR
•
A test signal is being injected to the PA with
+19 dBm.
Connect an antenna or dummy load to the RF
port (50 ohm impedance). Use the carrier frequency
needed.
1. Set RV501 on the PA fully counterclockwise.
Set RV502 on the PA fully clockwise, see
Figure 7-3.
2. Set Forward Power Adjust RV601 and Reflected
Power Adjust RV602 on the power detector board
fully counterclockwise (see Figure 7-3).
3. Monitor the voltage on R45 on the RFIB and set
R76 for 1.3V DC (see Figure 7-4). This sets the cur-
rent limit point for driver Q501 at hot temperatures.
4. Set each of the quiescent currents for Q502 and
Q503 for 10 mA (DC) each.
5. Program the power output for the correct frequency
range as follows:
132-150 MHz 110W
150-178 MHz 110W
6. Press the space bar to key the PA. Output power
will be approximetly 80W.
7. Monitor the output power and tune C601 and C602
for maximum output power (see Figure 7-3).
8. Set Forward Power Adjust RV601 for rated power
(110W or 100W).
9. Press the space bar to unkey the PA.
10.Disconnect the antenna or dummy load from the RF
port.
11. Press the space bar to key the PA.
NOTE: This will not harm the PA.
12.Adjust Reverse Power Calibration Pot RV602 for
equal voltages on W121 and W126 on the RFIB or
for equal Forward and Reverse Power
(see Figure 7-4).
13.Press the space bar to unkey the PA.