User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-16
5.12.13 (A11-A2) VHF Filter/Mixer
Board (1153-1101; Appendix D)
Typically a +15dBm RF input at J3, a
0dBm combined IF input at J7, and a RF
output of 0dBm at J2.
To align the board:
1. Monitor J4, the LO output of the
board, with a spectrum analyzer
and adjust C12 and C18 for
maximum output (+14 dBm) at
the LO frequency and minimum
out-of-band products. Adjust C13
and C17 for the best frequency
response for the LO frequency.
2. Adjust C3 and C6 to determine
the center frequency. Use C2 and
C7 to locate the upper and lower
channel-edge shaping. C4 is used
to determine the channel
bandwidth.
5.12.14 (A11-A3) VHF Low-Band
Filter/Amplifier Board (1064251;
Appendix D)
The filter/amplifier board has been
factory swept and adjusted for a 6-MHz
bandwidth.
NOTE: This board should not be tuned
without the proper equipment.
The output of the filter/mixer board
connects to the board at J7 (0dBm). It is
filtered on the board with the filtered
output connecting to J1 on the board that
is amplified by U1 to a nominal +12 dBm
visual and +2 dBm aural level set by
adjusting R9. The output at J2 is fed to
J4 on the A11 enclosure and from there
to J15 the RF output jack on the rear of
the tray.
To align the board, use a multiburst or
sweep video signal inserted into the
exciter tray.
Check that there is a cable connected
from J6 to J1 on the filter/amplifier
board. Monitor J2, the RF output of the
board, and peak C17 for the maximum
signal level. Tune the manual gain
adjust R9 for a +12 dBm peak visual
output.
This completes the detailed alignment
procedure for the VHF Exciter Tray, the
VHF L.B. Amplifier Tray, and also the
detailed alignment procedures for the
entire 335B transmitter. If a problem
occurred during the alignment procedure,
please call Axcera field support at 724-
873-8100 for assistance.