Alignment Without Vits Present - Standard Communications TVM Series Owner's Manual

Installation and Operation
Video Modulation Adjustment
1. Make sure the video signal applied to the rear panel of the modulator is
1.0 V p-p. If vertical interval test signals (VITS) are not present, set the sync
level for 0.285 V p-p, or –40 IRE. Refer to Figure 4-3.
2. Look at the VIDEO OVER MOD LED to see if it is lit or just flickering on and off.
•
If the LED flickers, rotate the VIDEO MODULATION adjustment CCW, to
the point where modulation just peaks and does not light the LED.
•
If the VIDEO OVER MOD LED does not light at all, turn the VIDEO
MODULATION adjustment CW until the LED just starts to flicker, indicat-
ing modulation peaks. Then, back off the adjustment (CCW) until the
flickering just ceases.
•
If the VIDEO OVER MOD LED is lit continuously, rotate the VIDEO
MODULATION adjustment CCW until the LED just starts to flicker. indi-
cating modulation peaks. Then, further rotate the adjustment CCW until
the flickering just ceases.
MV
800
600
0.715 V P-P
400
1.0 V P-P
200
0
SYNC. PULSE
(0.285 V P-P)
-200
40
NOTE: IF THE VERTICAL INTERVAL TEST SIGNALS (VITS) ARE NOT PRESENT,
Figure 4-3. Alignment Without VITS Present
Video/Audio Ratio Adjustment
1. Connect a spectrum analyzer to the –20 dB RF TEST jack on the modulator
front panel.
2. Observe the amplitudes of the video and audio signals.
3. Rotate the VIDEO/AUDIO RATIO adjustment until a minimum of –15 dBc is
achieved.
Page 4-6
IRE
120
110
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
0 20 40 60
SET SYNC. PULSE AMPLITUDE FOR 0.285 V P-P.
Owner's Manual
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TVM450/S/TVM550/S/TVM550II/TVM550IIS
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