User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-9
5.10 (A8) 3-Way Combiner Assembly
(1065241; Appendix C)
There are no adjustments to (A8) the 3
way combiner assembly.
5.11 (A14) Bandpass Filter Assembly
(1304388; Appendix C)
The harmonic and bandpass filters are
factory swept by the filter manufacturer
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.
5.12 Complete Board Level
Alignment Procedures for the VHF
Low Band Exciter
NOTE: The following procedure should
be fallowed only if complete alignment
of the VHF exciter tray is needed.
5.12.1 (Optional) 4.5-MHz
Composite Input Kit
If the (optional) 4.5-MHz composite input
kit is purchased, the tray is capable of
operating by using either the 4.5-MHz
composite input or the baseband audio
and video inputs. The kit adds the (A24)
composite 4.5-MHz filter board (1227-
1244; Appendix D) and the (A25) 4.5-
MHz bandpass filter board (1265-1307;
Appendix D) to the transmitter. When the
4.5-MHz intercarrier signal generated by
the 4.5-MHz composite input has been
selected by the 4.5-MHz composite input
kit, the 4.5-MHz generated by the aural
IF synthesizer board is not used. When
the 4.5-MHz intercarrier signal generated
by the baseband video and audio inputs
with baseband has been selected by the
4.5-MHz composite input kit, the
composite 4.5-MHz filter board and the
4.5-MHz bandpass filter board are not
used.
The tray has been factory tuned and
should not need any alignments to
achieve normal operation. To align the
tray for the 4.5-MHz composite input,
apply the 4.5-MHz composite input, with
the test signals used as needed, to the
video input jack (J1 or J2 [loop-through
connections]) on the rear of the tray.
Select the 4.5-MHz composite input by
removing the baseband select from J18-6
and J18-7 on the rear of the tray.
To align the exciter using baseband video
and audio inputs, apply the baseband
video, with the test signals used as
needed, to the video input jack (J1 or J2
[loop-through connections]) and the
baseband audio to the proper baseband
audio input on the rear of the tray. For
balanced audio input, connect TB1-1(+),
TB1-2(-), and TB1-3 (GND). For
composite/stereo audio, connect the
composite audio input jack (J3 or J13
[loop-through connections]) and connect
a baseband select from J18-6 and J18-7
on the rear of the tray.
5.12.2 (A6) Delay Equalizer Board
(1227-1204; Appendix D)
The jumper W1 on J5 of the sync tip
clamp/modulator board, if present, must
be in the Enable position between pins 2
and 3.
NOTE: This board has been factory tuned
and should not be retuned without the
proper equipment.
To tune this board:
1. Connect a sinX/X test signal into
jack J1-2 on the delay equalizer
board.
2. Monitor the video output of the
board, at the video sample jack J2,
with a video measuring set, such as
the VM700, adjusted to measure
group delay.
3. Tune the four stages of the board
using the variable inductors (L1-L4)