User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-15
of the transmitter. R103 and R106
are used to adjust the depth and
width of the correction notch.
9. The linearity correctors are set up
during the system alignment
procedure. Controls R13, R18, and
R23, the magnitude controls,
should be set fully CW. Controls
R34, R37, and R40 are the linearity
cut-in adjustments.
5.12.11 (A14-A1) Channel Oscillator
Board, Dual Oven (1145-1201;
Appendix D)
NOTE: If your transmitter contains a
precise frequency control system, a
VCXO Channel Oscillator Board (1145-
1204) will replace the Channel Oscillator
Board. Refer to the precise frequency
control instruction manual for set up
details.
This board is mounted in (A14) the
channel oscillator assembly (1145-1202).
To align the board:
1. Connect the main output of the
channel oscillator (J1) to a
spectrum analyzer, tuned to the
crystal frequency, and peak tuning
capacitors C6 and C18 for
maximum output. Tune L2 and L4
for maximum output. The output
level should be about +5 dBm. The
channel oscillator should maintain
an oven temperature of 50° C.
If a spectrum analyzer is not
available, connect a digital
voltmeter (DVM) to TP1 on the x4
multiplier board. Tune capacitors
C6 and C18 for maximum voltage,
then also tune L2 and L4 for a
maximum voltage output at TP1.
2. Connect the sample output of the
channel oscillator (J2) to a suitable
counter and tune C11, coarse
adjust, and C9, fine adjust, to the
crystal frequency.
3. Reconnect the main output (J1) of
the channel oscillator (+5 dBm) to
the input (J1) of the x2 multiplier.
NOTE: Do not repeak C6, C18, L2, or
L4. This may change the output level.
NOTE: While adjusting C9 and C11 to
the crystal frequency, the peak voltage
monitored at TP1 of the x2 multiplier
board should not decrease. If a decrease
does occur, there may be a problem
with the crystal. Contact Axcera Field
Support for further instructions.
NOTE: If the VCXO board (1145-1204) in
the VCXO assembly (1145-1206) is used,
the fine-frequency adjust C9 is not
located on the VCXO board. It is located
in the precise frequency tray. Refer to
the precise frequency control instruction
manual for set up details.
5.12.12 (A11-A1) x2 Multiplier Board
(1172-1111; Appendix D)
While monitoring the board with a DC
voltmeter, maximize each test point
voltage by tuning the broadband
multipliers in the following sequence:
1. Monitor TP1 with a DVM and tune
C4 for maximum voltage. Monitor
TP2 with a DVM and tune C6 for
maximum voltage. Repeak C4 and
C6 for maximum voltage.
2. Connect a spectrum analyzer,
tuned to two times the crystal
frequency, to the x2 multiplier
output jack J2. While trying to
keep the out-of-band products to
a minimum, monitor the output
and peak the tuning capacitors for
maximum output.
The output of the x2 multiplier (+15dBm)
connects to (A11-A1) the filter/mixer
board.