Axcera-430B FCC Type Acceptance Report Parts List/Tune-up Info
February 2004
7-6
metering board (1265-1309), fully CCW. Adjust R48, the null offset pot on the visual/aural
metering board, for 0% Visual Output. Perform the following adjustments with no aural
present; this is accomplished by removing jumper cable W1, the aural IF loop-through,
that is connected to J16 on (A5) the sync tip clamp/modulator board (1265-1302).
Connect a sync and black test signal to the video input jack of the VHF exciter tray.
Switch the transmitter to Operate.
Set up the transmitter for the appropriate average output power level: sync + black 0 IRE
setup/wattmeter=595 watts; sync + black 7.5 IRE setup/wattmeter=545 watts.
Note: The transmitter must have 40 IRE units of sync.
With the front panel meter in the % Visual Output position, adjust R28, visual calibration,
on (A19) the visual/aural metering board (1265-1309) for 100%.
With the spectrum analyzer set to the zero span mode, obtain a peak reference on the
screen. Reconnect jumper cable W1 to J16 on (A5) the sync tip clamp/modulator board.
While in the Visual Output Power position, adjust L3 for a minimum visual power reading.
Turn the power adjust pot on the front panel until the original peak reference level is
attained. Peak L1 and C8 for a maximum aural power reading and then also adjust R20 for
a 100% Aural Power reading. Switch the transmitter to the Visual Output Power position
and adjust R51, the aural null pot, for 100% Visual Power.
7.2.8 Calibration of the Reflected Output Level of the Transmitter
On the meter, in the Visual Power position, turn the power adjust pot to 20%. Check that
the jumper is in Manual on the VHF filter/amplifier board (1064252). Reverse the cables on
A9-A5, J3 and J4, and adjust R39 on the visual/aural metering board (1265-1309) for a
20% reading in the Reflected Power position. At this 20% reference power reading, the
VSWR LED mounted on the front panel of the exciter should be illuminated. If this LED is
not lit, adjust R22 on the transmitter control board in the VHF exciter tray until the VSWR
LED just turns on. Turn the power adjust pot slightly CCW and the LED should go out.
Turn the pot CW until the LED just turns on. The reflected output power is now
calibrated.
Switch the transmitter to Standby. Move the cables on A9-A5, J3 and J4, to their original
positions. Switch the transmitter to Operate and adjust the front panel power pot for a
100% Visual Power reading.
7.2.9 2-Way Combiner Assembly
There are no adjustments to (A8) the VHF combiner assembly (1219-1006).
Note: The bandpass filter is factory swept and should not be tuned without the
proper equipment. Do not attempt to tune the filters without a sweep generator
or, preferably, a network analyzer. If tuning is required, consult the Axcera Field
Support Department before attempting to make any adjustments.
7.2.10 Bandpass Filter Assemblies
The input to (A13) the bandpass filter assemblies (1076294 through 1076297) is the
output of the VHF combiner assembly, which is the combined output of the VHF amplifier
trays. The filter is made of aluminum waveguide and has five resonant cavities. The filter
has five bolts for tuning adjustments. The bandpass filter also utilizes two integral traps
at -4.5 MHz and +9 MHz from F
V
. Refer to the bandpass filter drawing for the location of
the adjustments.
Summary of Contents for 430B
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