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OTM-3000-CV
FREQUENCY AGILE - F.C.C. COMPATIBLE
TELEVISION MODULATOR
INSTRUCTION MANUAL
Phone:
E-Mail: [email protected]
025-000041 REV C 8/23/01
(209) 586-1022
(800) 545-1022
Fax:
(209) 586-1026
www.olsontech.com
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1) INTRODUCTION
The OTM-3000 CV is a frequency agile F .C.C. compatible television modulator with an output frequency
range of 55.25MHz through 445.25MHz (channel 2 through cable channel YY). All channels are selectable
by front panel DIP switches, including F .C.C. offsets of +12.5KHz and +25KHz.
The OTM-3000 CV offers high output level, typically +60dBmV. This unit has a very high out-of-band carrier
to noise ratio (>80dB) and uses SA W I.F . filtering, which allows virtually an unlimited number of modulators to
be combined without the need for external bandpass filters. The OTM-3000 CV has low power consumption
(12 watts @ 115 V AC) for reliable long term operation.
The OTM-3000 CV will perform with seperate baseband audio and video input or a composite video (CV)
input or an external 4.5MHz input.
The unit is shipped for operation in the CV modes. An internal toggle switch controls separate baseband video
and audio inputs and composite (CV) operation. The toggle switch is located on the center divider internal to
the chassis.
OTM-3000 CV
FREQUENCY AGILE - F .C.C. COMP ATIBLE
TELEVISION MODULA TOR
1) For CV operation, the switch should be in the position toward the front of the chassis.
2) For standard operation, the switch should be toward the rear of the chassis.
For composite video application, connect the composite video source to the “composite video input” jack.
Cable the “video only” output to the “video” input. The unit will automatically construct the 4.5MHz carrier if
the 4.5MHz carrier is present with the video. Adjust the video modulation level with the front panel video
modulation control. The audio modulation control is inoperable in the CV mode.
For external 4.5MHz operation, connect the 4.5MHz source to the “composite video input”. T erminate the
“video only” output. Connect the baseband video source to the “video input”.
2) CHANNEL/F .C.C. OFFSET SELECTION
Channel selection is made by properly setting the two 8-position switches to the corresponding channel
code. Select the desired channel/offset code from Figure #1 or the code card attached to the “Channel
Select” cover plate, then set the DIP switches from left to right. The 13 left-most switches are channel
select.
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Figure 1
OTM-3000-CV
CHANNEL SELECT CHART
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4) F .C.C. OFFSET FREQUENCIES
5) VIDEO MODULA TION 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).
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.
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6) AUDIO MODULA TION 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, set the video carrier to the desired level with the RF output level adjust
control.
B) Tune the field strength meter to the aural carrier (4.5MHz 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) The OTM-3000 CV is BTSC stereo compatible. It is shipped in the “mono” mode. T o defeat pre-
emphasis, in order to use a composite BTSC baseband input signal, move the internal jumper plug
from W2 “PRE” to W2 “BY”. This plug is located in the left front area of the circuit board.
B) 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 CV will not perform
properly .
C) If a scrambling unit is utilized with the OTM-3000, follow the instructions associated with the scram-
bler. 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.
D) This unit is equipped with a 0.5A slo-blo fuse. For continued safety and to maintain proper perfor-
mance of the unit, please replace only with an equivalent fuse.
E ) A -20dB test point (type F connector) is provided in the rear panel.
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MODULA TOR SWITCH SETTING CALCULA TION
The output frequency select switches may tune a unit in either 1MHz or 250KHz steps depending on the factory
presetting of step size. T o calculate the switch settings for a unit, the formula is as follows:
N = OUTPUT FREQUENCY + 2ND IF FREQUENCY 2ND IF FREQUENCY
STEP SIZE IN MHz ALL NTSC = 612.75
ALL P AL = 605.75
OR FOR 1MHz STEP SIZE
N =
OUTPUT FREQUENCY + 612.75
1
OR FOR .25MHz STEP SIZE
N = OUTPUT FREQUENCY + 612.75
0.25
Convert the number “N” to binary with the least significant bit on the left, (not the right as is customary). This binary
number represents the switch settings with 1 = UP , 0 = DOWN.
BINAR Y CONVERSION WITH LEAST BIT ON LEFT.
————————————————————————————————————————————
EXAMPLE: CALCULA TE 437 IN BINAR Y
STEP 1) CONSUL T CHAR T FOR LARGEST NUMBER LESS THAN OR EQUAL TO 437. (256)
STEP 2) CONSULT CHAR T TO FIND NEXT LARGEST NUMBER WHICH ADDED T O 256 IS LESS
THAN OR EQUAL TO 437. (128 + 256 = 384)
STEP 3) CONSULT CHAR T TO FIND NEXT LARGEST NUMBER WHICH ADDED T O 384 IS LESS
THAN OR EQUAL TO 437. (384 + 32 = 416)
STEP 4) CONSULT CHAR T TO FIND NEXT LARGEST NUMBER WHICH ADDED T O 416 IS LESS
THAN OR EQUAL TO 437. (416 + 16 = 432)
STEP 5) CONSULT CHAR T TO FIND NEXT LARGEST NUMBER WHICH ADDED T O 432 IS LESS
THAN OR EQUAL TO 437. (432 + 4 = 436)
STEP 6) CONSULT CHAR T TO FIND NEXT LARGEST NUMBER WHICH ADDED T O 436 IS LESS
THAN OR EQUAL TO 437. (436 + 1 = 437)
STEP 7) EACH NUMBER CHOSEN = CODE 1 AND EACH NUMBER NOT CHOSEN = CODE 0.
X X X X X X
1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192
437 = 1 0 1 0 1 1 0 1 1 0 0 0 0 0
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