Olson Technology OTD-3000-DC - Manual (Page 4)

025-000128 REV B Page 4
4) OFFSET OPERATION
The last 3 positions of the right hand DIP switch, SW2, are used to select offset operation with certain versions
of the OTM-3000. On the OTM-3000 DC, the last 3 switch positions should be left set as shown above.
5) VIDEO MODULATION ADJUSTMENT
A) Connect a video source of approximately 1V p-p to the video input connector (75 ohms input Z) on
the rear panel. The video should be of a reasonably bright scene.
B) Rotate the video modulation level adjust control slowly clockwise until the video overmodulation LED
just turns on. The light may blink with differences in average picture level. CAUTION: If the
modulation is set too high, compression or lack of contrast will occur during high intensity scenes.
6) AUDIO MODULATION ADJUSTMENT
A) Connect an audio source of 300mV p-p (minimum) to the balanced audio input connector (600 ohms
input Z) on the rear panel. The source should be typical of the program material to be carried.
B) Rotate the audio modulation level adjust control slowly clockwise until the audio overmodulation LED
just begins to blink. CAUTION: Overmodulation can result in severe distortion in some TV sets. Set
this control at peak program levels.
7) RF AND AURAL CARRIER LEVEL ADJUSTMENT
A) Using a field strength meter or spectrum analyzer, set the video carrier to the desired level with the RF
output level adjust control.
B) Tune the field strength meter or analyzer to the aural carrier (6.5mHz above the video carrier).
C) Adjust the aural carrier level control to the desired level, typically 15dB below the video carrier.
CAUTION: Reducing the visual/aural carrier ratio to less than 15dB can result in high out-of-band
spurious signals in adjacent channels.
8) MISCELLANEOUS
A) This unit is equipped with video and audio I.F. loops. Both loops are connected with two type F
short jumpers. If these become disconnected or misplaced, then the OTM-3000 DC will not
perform properly.
B) If a scrambling unit is utilized with the OTM-3000 DC, follow the instructions associated with the
scrambler. The video I.F. output level is +40dBmV, and the audio carrier level is determined by the
aural carrier level adjustment - typically +17dBmV @ 15dB A/V ratio.
C) This unit is equipped with a 0.25A slo-blo fuse. For continued safety and to maintain proper
performance of the unit, please replace only with an equivalent fuse.
D) A -20dB test point (type F connector) is provided on the rear panel.