Vector-LP Radio Beacon Transmitter Technical Instruction Manual Page 4-13
Section 4 Testing and Adjustment Issue 1.1
NOTE
If an external RF generator is producing
the RF drive, verify its output waveform is
symmetrical.
4.3.6.10 EQUALIZING EXCITER GAIN
(Dual Side Transmitters Only)
If the RF output of the transmitter varies
between side A and B, you may need to
equalize the exciter gain. Equalize the
PDM pulse train between sides A and B so
that no change in RF output level occurs
during exciter changeover, as follows:
(a) Go to the Power Module Status menu
(see 3.6.13.2).
(b) Use an oscilloscope to monitor TP17 of
interphase PDM driver PWB A (A6).
(c) On interphase PDM driver PWB A
(A6), adjust the GAIN TRIM
potentiometer (R31) four turns counter
clockwise and one and a half turns
clockwise. On interphase PDM driver
PWB B (A9), adjust the GAIN TRIM
potentiometer (R31) four turns counter
clockwise.
(d) Press RF On. Increase the
transmitter’s RF output to full rated or
maximum power, whichever is lower.
(e) Use an external current probe to
measure RF output power:
Power = Current
2
x R
load
(f) In the Maximum Output Gain menu
(see 3.6.12.3), calibrate the duty cycle
and forward power as follows:
x Highlight the value for Set Duty Cycle.
Press Modify.
x Change the value to match the positive
duty cycle measured at TP17 in step
(c). Press Next.
x Change the value for Set Forward
Power to match the power calculated
in step (e). Press Done.
(g) If the transmitter is operating at full
power, go to step (o). If not:
x Highlight the value for Maximum
Carrier Reference. Press Modify.
x Increase the value by 5. Press Done.
(h) Repeat step (e).
(i) Set the maximum carrier reference:
x Record the current duty cycle and
forward power values.
x Record the power according to the
external current probe.
x Highlight the value for Maximum
Carrier Reference. Press Modify.
x Adjust the value to 1 higher than the
current Carr. Ref value. Press Done.
(j) Increase the power until maximum
power is reached. Record the power
level on the top line (status bar) of the
GUI display.
(k) Press Power Increase and Power
Decrease at the same time to set the
RF power to 0 W. Press RF Off.
(l) Select side B in the Changeover
Control menu.
(m) Press RF On. Ensure all side B RF
power module fans are on.
(n) Press Power Increase until you reach
maximum power. Adjust GAIN TRIM
potentiometer R31 on interphase PDM
driver PWB B (A9) to ensure that the
output power matches the output
power recorded in step (j).
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