Olson Technology OTM-3550 User Manual

OTM-3550-B/G

FREQUENCY AGILE PAL B/G

TELEVISION MODULATOR

INSTALLATION MANUAL

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1) INTRODUCTION

The OTM-3550 B/G is a frequency agile television modulator with an output frequency range of 48.25MHz through

547.25MHz. All channels are selectable by front panel DIP switches in 1MHz increments.

The OTM-3550 B/G offers high output level, typically +55dBmV. This unit has a very high out-of-band carrier to noise
ratio (>77dB) and uses SAW I.F. filtering, which allows virtually an unlimited number of modulators to be combined
without the need for external bandpass filters. The OTM-3550 B/G has low power consumption (12 watts @ 220 VAC)
for reliable long term operation.

2) CHANNEL SELECTION

Remove the front panel plate marked “CHANNEL SELECT” to expose the channel select DIP switches as shown in figure
#1. Output frequency selection is accomplished by setting these DIP switches to the correct code for the desired channel.
Locate the code for the desired channel frequency in Table 1 in this manual and set the DIP switches from left to right (The
13 left-most switches are used for channel selection).

OTM-3550-B/G

FREQUENCY AGILE PAL B/G

TELEVISION MODULATOR

CHANNEL SELECT OFFSET

0 0 1 1 0 1 0 0 1 1 0 0 0 0 1 1

0 = Switch in DOWN Position
1 = Switch in UP Position

Figure 1 Front panel DIP switches

The above example indicates proper switch settings for 206.25MHz

3) OFFSET OPERATION

The last 3 DIP switches on the far right are used to select offset operation with certain versions of the OTM-3000. On the
OTM-3550 B/G, the switch should be left set as shown below.

4) 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 (commercials are usually excellent).

0 1 1

B) Rotate the video modulation level control slowly clockwise until the video over modulation 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.

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5) 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 control slowly clockwise until the audio over modulation LED just begins to blink.

CAUTION: Over modulation can result in severe distortion in some TV sets. Set this control at peak program levels.

6) 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 (typically +50 to +55dBmV).

B) Tune the field strength meter or analyzer to the aural carrier (5.5mHz 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.

7) 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-3550 B/G will not perform properly.

B) If a scrambling unit is utilized with the OTM-3550 B/G, 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.

E) When installing OTM-3550 B/G in any equipment rack it is best to leave an empty rack space above and below the unit
to allow for optimum air circulation.

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