User's Manual

351804-1 Rev. 100
COM5000-8 TECHNICAL MANUAL
40
1.25kW PA Module
RF OUTPUT “T” connector (direct at Wattmeter)
Connector
h) Starting with a low RF output level from the RF Signal Generator increase the generator level until
the forward power reading is 500W.
i) Measure the voltage on U20-1 (VF). Adjust VR5 so the voltage measured on U20-7 is equal to the
voltage at U20-1.
j) Measure the voltage on U20 pin 7. Adjust VR7 such, that the voltage measure on U20 pin 10 is 1/2
of the voltage measured on U20 pin 7.
k) Un-key the system. Set up for operation into one 50 Ohm load.
l) Key the system. Increase the RF drive level to obtain an output power of 1250 W.
m) Proceed to perform this adjustment on the PA Controller PCB Assembly with 1250 W output:
VF: Set VR6 for a reading of 2.00 V measured on U20A pin 1.
VFL: Set VR8 for a reading of 1.00 V measured on U2 pin 3.
DRVR Q1FLT Window Comparator:
This adjustment requires the Driver bias current adjustment to have been completed. See paragraph
5.4.1.4.
a) Operate the PA Module as a “stand alone” Amplifier – while still part of the Transmitter - as
described in section 5.4.1 above.
b) Turn ON the System. With the system un-keyed, measure and record the DC voltage on U17 pin 4.
c) Measure the DC voltage at U17 pin 5 and adjust VR9 for a voltage 0.05 V below the voltage
measured on U17 pin 4.
d) Select an operating frequency of 29.9 MHz and key the transmitter
e) Adjust the RF Signal Generator level to obtain a power output of 1250 W. Wait for the initial drift in
power to settle in order to get a reasonably stable 1250 W power.
f) Measure and record the DC voltage at U17 pin 9.
g) Measure the DC voltage at U17 pin 8 and adjust VR10 for a voltage 1.5 V below the voltage
measured at U17 pin 9.
50 Ohm
Load
50 Ohm
Load
Wattmeter