Pulsar LPA100, Системное руководство

Страница: 58 / 66

Page 9–2
June 2001
50W / 100W Linear Power Amplifier
Technologies, Inc.
9.2 50W Combiner Modules Test
Points
9.2.1 Preliminary checks
In order to check that all 4 of the 12.5W Power
Amplifiers are balanced with one another, their
output levels must be checked on the input test
points of the 50W Power Combiner module.
Measure between any one of the four Power
Combiner input test points (orange, yellow, white,
& blue - see Figure 9-1) and the common test
point (black) in order to verify that the levels are
equal to one another and approximately 26Vrms
(41.3 dBm, 50
Ω
reference). If not then the serial #
sticker must be removed from the front of
whichever 12.5W Power Amplifier that needs to
be adjusted in order to adjust its front panel input
potentiometer.
Before turning the LPA power on, set up to
measure the corresponding Power Combiner input
test point for the 12.5W Power Amplifier. Then
after turning the power on, quickly adjust the
input potentiometer on the 12.5W Power
Amplifier to be the same level as the other three
amplifiers on the Power Combiner input test
points. Any difference in power level at these 4
test points will be dissipated in the Power
Combiner high wattage resistors. It's important to
balance these levels as close to equal as possible
in order to maximize transfer of signal power to
the line tuner.
9.2.2 In-service checks
Read between the red and black test points (50W
output) on the 50W Power Combiner module (see
Fig. 9-1). The level should be at /- 1V
(+47.0 dBm +/- 0.3dB, 50
Ω
reference) which is
equal to 50W output for a 50
Ω
load. This level
should be approximately 6 dB higher than the 4
equal levels on the input test points of the Power
Combiner. If this level needs to be slightly
changed, then adjust the driving carrier set
amplifier's INPUT level potentiometer again.
Then recheck the level on the INPUT test point of
one of the 12.5W Power Amplifiers to make sure
it doesn't exceed 1Vrms (+13.0 dBm, 50
Ω
reference) as set in the previous step. It is recom-
mended that the 50W output level be measured
with an oscilloscope to verify the accuracy of the
selective level meter and also to check that the
output sine wave is not distorted. This is important
because a 6.2Vrms or 1 dB difference in level is
equal to being off by 13 watts.
!
CAUTION
BE CAREFUL TO NOT LET THE TEST POINTS
SHORT TOGETHER SINCE THEY ARE PHYSI-
CALLY CLOSE TOGETHER.
Figure 9–1. 50W Combiner Module
TP4 PA#1 IN1, ORANGE
TP3 PA#2 IN2, YELLOW
TP1 COMMON, BLACK
INJECT/EJECT
LEVER
COMPONENT SIDE
SOLDER
SIDE
TP2 PA#4 IN4, BLUE
TP5 PA#3 IN3, WHITE
TP6 OUTPUT, RED
NOTE
To maximize the efficiency of your TC-
10B/TCF-10B system it is important to verify
the equalization of the power amplifiers via
the 50W combiner modules’ test points. A
difference as small as 6.2Vrms or 1 dB
between power amplifiers outputs is equal to
losing 13 watts of power.