Vector-LP Radio Beacon Transmitter Technical Instruction Manual
Page
4-11
Section 4 Testing and Adjustment
Issue 1.1
NOTE
When you exit the Calibrate Meters menu a
message is displayed indicating that you
have made changes. You will be prompted
to save the changes to EEPROM so that
they can be restored in the event of a
power failure. Press
Yes
each time this
prompt is displayed during the setup
procedure.
During initial turn-on and adjustment of
transmitter power, the diagnostic display’s
meters screen should be monitored.
4.3.6.5 CALIBRATING PDM
(a) Use an oscilloscope to monitor TP17 of
the active interphase PDM driver PWB
(A6 for side A or A9 for side B).
(b) Press
RF On
. Set modulation to 0%.
(c) In the Calibrate Meters menu (see
3.6.12 and 3.6.12.1) scroll through the
parameters until
PDM A
(or
PDM B
,
depending on the transmitter’s active
side) is highlighted. Press
Modify
.
(d) Adjust the value to match the positive
duty cycle measured on TP17 in step
(a). Press
Done
.
4.3.6.6 CALIBRATING REFLECTED
POWER THRESHOLD AND OUTPUT
NETWORK ALARM
(a) Turn off the transmitter and disconnect
the dummy load from the transmitter’s
RF output. Short the transmitter’s RF
output to ground near the RF output.
Install the external current probe on the
shorting jumper.
(b) In the Set Thresholds menu (see
3.6.12 and 3.6.12.2) set the
Slowback
Pwr (Per Block)
value to 100 W.
(c) Set RF output power to 0 W. Press
RF
On
. Monitor the external current while
slowly increasing the power to half of
the reflected power limit. Try to achieve
a current of 1.8 A (should occur at
approximately 40 W).
(d) Calculate the actual reflected power
using the following equation:
Refld Pwr = (I
short circuit
/ 2)
2
x 50
:
(e) In the Calibrate Meters menu (see
3.6.12 and 3.6.12.1) scroll through the
parameters until
Reflec. Power
is
highlighted. The
Reflec. Power
value
should be within 20% of the value
determined in step (d).
x
Press
Modify
.
x
Adjust the value to match the level
calculated in step (d). Press
Done
.
(f) Press
Back
and select
Set
Thresholds
.
(g) Press
f
,
g
or
Next
until
Refl. Power
Shutback
is displayed.
x
Monitor the external current while
slowly increasing the power to the
reflected power limit. Try to achieve a
current of 2.5 A (should occur at
approximately 80 W).
(h) If an
Output Network
alarm occurs
before reaching the reflected power
limit, increase the
Refl. Power
Shutback
threshold level and press
Done
and return to step (h). Otherwise
continue to step (j).
(i) Decrease
the
Refl. Power Shutback
threshold level until the
Output
Network
alarm occurs. Press
Done
.
(j) In the Set Thresholds menu, set the
Slowback Pwr
to 30 W (for VR250) or
15 W (for VR125).
