Data Sheet Chapter 5

4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-9
manual offset, for the correct depth
of modulation by observing the
demodulated waveform on the
waveform monitor or on the
spectrum analyzer set to zero span.
10. Check the demodulated video for
the proper sync-to-video ratio (sync
is 28.6% of the total white video
signal). If sync stretch is needed,
adjust R45, sync stretch cut-in,
until sync stretch occurs. Adjust
R48, sync stretch magnitude, for
the proper amount of stretch.
Readjust R41, manual offset, if
necessary, for the correct depth of
modulation.
11. Move jumper W7 on J4 to the clamp
enable position. Readjust pot R152,
the depth of modulation, for the
correct depth of modulation.
12. Set the waveform monitor to
display ICPM. Preset R53 fully CCW,
adjust C78 for the greatest effect at
white on the ICPM display, and
adjust R53 for minimum ICPM.
13. Recheck the depth of modulation
and, if necessary, adjust R152,
depth of modulation.
14. Adjust pot R70 for a level of
approximately -10 dBm on the
spectrum analyzer at J18.
15. Remove the video input. Place the
front panel meter in the video
position and, while monitoring the
meter, adjust pot R144, zero
adjust, for a reading of zero.
16. Replace the video input test
signal (the 5-step staircase).
Turn the front panel meter to
the Video position and adjust
R20 on the transmitter control
board for a reading of 100 (10
on the 0-to-10 scale). This
board does not have sync
metering.
17. Reconnect the plug to J18 and
move the spectrum analyzer test
cable to 41.25 IF output jack J16.
Tune C59 and L17-L20 to maximize
the 41.25-MHz aural IF signal and
minimize the out-of-band products.
Adjust pot R97 for -20 dBm at J16.
18. Reconnect the plug to J16 and
move the spectrum analyzer test
cable to IF output jack J20. Preset
R62, the visual IF gain pot, to the
middle. Insert a multiburst test
signal into the translator and
observe the visual frequency
response with the spectrum
analyzer set at 1 dB/division. Tune
R63 and C30, the IF frequency
response adjustments, for a flat-
frequency response (±0.5 dB).
19. While still monitoring J20 with a
spectrum analyzer, readjust R62,
visual IF gain, for a visual output
level of 0 dBm. Adjust R85, A/V
ratio, for a -10 dB aural-to-visual
ratio or to the needed A/V ratio.
Reconnect the plug to J20.
20. Using an input video test signal (the
5-step staircase) with a 100 IRE
white level, monitor TP2 with an
oscilloscope. Set the control R24,
the sync clip, just below the point
where sync clipping begins to occur.
Also, set R20, the white clip, to the
point just below where the white
video begins to clip.
Note: This procedure should be
performed after the system setup or
if linearity problems occur.
5.3.6 (A4) (Optional) Aural IF
Synthesizer Board, 4.5 MHz (1265-
1303, Appendix D)
1. The test equipment setup for (A4)
the aural IF synthesizer board, 4.5
MHz, is as follows:
A. Connect a 600-Ω balanced
audio output from an audio
oscillator to the balanced audio