User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-10
and potentiometers (R7, R12, R17,
and R22) until the signal attains the
FCC group delay curve. The stages
are arranged in order of increasing
frequency. Adjust R29, as needed,
to attain the same level out of the
board as into the board.
5.12.3 (Optional) (A24) Composite
4.5-MHz Filter Board (1227-1244;
Appendix D)
This board is part of the 4.5-MHz input
kit and will only function properly with a
4.5-MHz composite input signal and the
4.5-MHz composite input selected. To
align this board:
1. Connect the test signal from an
envelope delay measurement set to
the video input of the tray at J1 or
J2.
2. Connect an oscilloscope to jack J7,
video out, between the J7 center
pin and pin 1 or 3 (ground). Adjust
C21, frequency response, if needed,
for the best frequency response.
Adjust R32, video gain, for a signal
level of 1 Vpk-pk on the
oscilloscope.
The output at J6 and J7 on the board
should be video only, without the 4.5-
MHz aural subcarrier.
5.12.4(Optional) (A25) 4.5-MHz
Bandpass Filter Board (1265-1307;
Appendix D)
This board is part of the 4.5-MHz input
kit and will only function properly with a
4.5-MHz composite input signal and the
4.5-MHz composite input selected. To
align this board:
1. Adjust the filter with L2, C3, L4,
and C7 for a frequency response of
no greater than ±0.3 dB from 4.4
to 4.6 MHz.
2. Adjust C19 for an overall peak-to-
peak variation of less than ±0.3 dB
from 4.4 MHz to 4.6 MHz.
3. Recheck the frequency response; it
may have changed with the
adjustment of the envelope delay.
If necessary, retune the board.
5.12.5 (A7) IF Carrier Oven
Oscillator Board (1191-1404;
Appendix D)
NOTE: If your transmitter contains a
precise frequency control system, an IF
VCXO Board (1248-1131) will replace the
IF Carrier VCXO Board. . Refer to the
precise frequency control instruction
manual for set up details.
To align this board:
1. While monitoring J3 with a
spectrum analyzer, observe the
45.75-MHz visual IF (typical +5
dBm).
2. Connect a frequency counter to J3
and adjust C17 for 45.750000 MHz.
3. Connect a frequency counter to J1
and check for 50 kHz, which is the
aural phase lock loop reference.
5.12.6 (A5) Sync Tip
Clamp/Modulator Board (1265-
1302; Appendix D)
To align this board:
1. Determine if jumper W4 on jack J3
is present. Jumper W4 terminates
the video input into 75Ω. Remove
jumper W4 if a video loop-through
is required on the rear chassis at
jacks J1 and J2.
2. Set the controls R20, the white clip,
R24, the sync clip, and R45, the
sync stretch cut-in, to their full
CCW position. Set R48, the sync
magnitude, fully CW and place the