Copyright 2005 ISC Technologies
6 ADJUSTMENTS
6.1 Power Amplifier Alignment and Tuning
6.1.1 Why You Need to Tune
The 9T97A250 RF power amplifier is factory adjusted at the desired frequency. If the fre-
quency of operation has to be changed by more than 2 MHz away from the previous fre-
quency, then the following adjustments should be made. This is to ensure the power am-
plifier’s optimum performance and increase the life of the RF power transistors.
6.1.2 Equipment
Needed
The following tools and equipment will be required to properly align the 9T97A250 RF
power amplifier.
•
Directional wattmeter, 50 ohms, 5-watts full scale, 5% accuracy.
•
Directional watimeter, 50 ohms, 250-watts full scale, 5% accuracy.
•
50-ohm termination 250 W.
•
Tuning tool, slot, insulated.
•
DC ammeter: 25 A full scale, 2.5% accuracy.
•
Cables with appropriate connectors.
•
Test set: M-97.
6.1.3 Exciter Check
1. Set up the exciter and test equipment as shown in Figure 6-1.
2. Switch ON the power supply and key the exciter. Check that the output power is 4.0
watts +/- 0.2 watts.
3. If the power output is not within this range, switch OFF the power supply and replace the
exciter.
6.1.4 Power Amplifier Adjustments
1. Switch ON the power supply and key the exciter.
2. Adjust C12 on the first final for maximum power.
3. Record the current reading of this final from the M-97 test set.
4. Increase the capacitance of C12 on the first final until the power drops by 2 watts from
the maximum power peak.
5. Check that the current reading has decreased on the M-97 test set.
6. Repeat steps 2 to 6 for the second final.
7. Repeat steps 2 to 6 for the third final.
8. Repeat steps 2 to 6 for the fourth final.
