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OTD-3000-DC
FREQUENCY AGILE
TELEVISION DEMODULATOR
PAL-D (China) STANDARD
INSTRUCTION MANUAL
Phone:
E-Mail: [email protected]
025-000105 REV B 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 DC is a frequency agile television modulator with an output frequency range of 48.25MHz
through 450.00MHz. All channels are selectable by front panel DIP switches in .25MHz increments.
The OTM-3000 DC 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 DC has low power consumption
(typically 12 watts @ 220 VAC) for reliable long term operation.
2) CHANNEL SELECTION
Output frequency selection is made by properly setting the two 8-position DIP switches SW1 and SW2 which
are located behind the small cover plate on the front panel.
OTM-3000 DC
FREQUENCY AGILE PAL D
TELEVISION MODULA TOR
Refer to T able 1 to determine the proper switch settings for various P AL D China channels. Set the
switches from left to right as shown in T able 1.
Figure 1 - SW1, SW2 Switch Functions
For example, if 49.75MHz is desired, the DIP switches would be positioned as follows:
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3) SELECTION OF NON-ST ANDARD OUTPUT FREQUENCIES
Refer to the following paragraphs if you need to set the switches for non- standard assignments.
Each of the switches has a weighted value as indicated in Figure 2. The switches are either
UP = OFF = (value) or are DOWN = ON = 0.
Figure 2 - SW1/SW2 Switch V alues
The selected video carrier frequency may be any frequency within the 48 to 450MHz band providing the selected
frequency (+) 605.75 is evenly divisible by .25. The procedure is as follows:
COMPUTING SWITCH SETTINGS FOR NON-ST ANDARD FREQUENCIES
A) Decide on the required frequency and check that it is evenly divisible by .25 (answer must end in .00).
B) Compute the total weighted switch value required.
C) Set the DIP switches to equal the total weighted value.
EXAMPLE:
If X is the required frequency in MHz and Y is the total weighted value of the switch settings, then (X + 605.75)
divided by .25 = Y.
T o illustrate: If the desired frequency is 49.75.
Y = (49.75 + 605.75) divided by .25 = 2622
Refer to Figure 2 and compute which switch positions must be moved UP so their total value = 2622. This would
yield switch settings of:
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Figure 3 - Example of settings for 49.75MHz.
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4) OFFSET OPERA TION
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 MODULA TION ADJUSTMENT
A) Connect a video source of approximately 1V p-p to the video input connector (75 ohms input Z) on
the rearpanel. 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 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 or spectrum analyzer, set the video carrier to the desired level with the RF
output level adjust control.
B) T une 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
D) A -20dB test point (type F connector) is provided on the rear panel.
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performance of the unit, please replace only with an equivalent fuse.
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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 PAL = 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 CHART T O FIND NEXT LARGEST NUMBER WHICH ADDED T O 256 IS LESS
THAN OR EQUAL TO 437. (128 + 256 = 384)
STEP 3) CONSULT CHART T O FIND NEXT LARGEST NUMBER WHICH ADDED T O 384 IS LESS
THAN OR EQUAL TO 437. (384 + 32 = 416)
STEP 4) CONSULT CHART T O FIND NEXT LARGEST NUMBER WHICH ADDED T O 416 IS LESS
THAN OR EQUAL TO 437. (416 + 16 = 432)
STEP 5) CONSULT CHART T O FIND NEXT LARGEST NUMBER WHICH ADDED T O 432 IS LESS
THAN OR EQUAL TO 437. (432 + 4 = 436)
STEP 6) CONSULT CHART T O 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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OTM-3000 DC
ST ANDARD CHINA P AL D CHANNELS
T able 1
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OTM-3000-DC ST ANDARD CHANNELS (continued)
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