LEAMING INDUSTRIES MTS-5 User manual

LEAMING INDUSTRIES MTS-5
BTSC STEREO GENERATOR
INSTRUCTION BOOK
IB 009095-01 C
ALL ENGINEERING DESIGNS, DRAWINGS AND DATA CONTAINED HEREIN ARE
PROPRIETARY. NO PART OF THIS BOOK MAY BE COPIED OR OTHERWISE USED
WITHOUT WRITTEN AUTHORIZATION
Copyright 7 September 2004
by
LEAMING INDUSTRIES
3972 BARRANCA PARKWAY, J608
IRVINE, CA 92606
[phone]

10 April 2002 MTS-5 PAGE 2of 21
MTS-5 TABLE OF CONTENTS
SECTION PARAGRAPH PAGE
1.0 QUICKSTART 3
2.0 INTRODUCTION TO THE MTS-5 3
3.0 INSTALLATION 4
3.1 AUDIO INPUT 4
3.1.1 SECOND (B) AUDIO INPUT 4
3.2 VIDEO SYNC IN CONNECTIONS 5
3.3 COMPOSITE BASEBAND OR 4.5 MHz FEED TO TV MODULATOR 5
3.3.1 BASEBAND STEREO MULTIPLEX TO TV MODULATOR 5
3.3.2 4.5 MHz AUDIO CARRIER WITH VIDEO 6
3.3.3 4.5 MHz AUDIO CARRIER SEPARATE FROM VIDEO 6
3.4 VIDEO SCRAMBLING 6
4.0 OPERATION 7
4.1 SETTING THE AUDIO CARRIER DEVIATION 7
4.1.1 SPECTRUM ANALYZER AND TEST TONE METHODS 7
4.1.2 USING THE METER OR PEAK FLASHER ON THE TV MODULATOR 8
4.2 AUDIO CARRIER LEVEL ADJUSTMENT 8
4.3 "A"/"B" AUDIO INPUTS 8
4.3.1 LOCAL & REMOTE AUDIO INPUT SELECTION 9
4.3.2 INTERNAL SAP "B" INPUT 9
4.4 STEREO AUDIO LEVELS and AGC CONSIDERATIONS 9
4.5 AUDIO AGC OK & HI INDICATORS 10
4.6 STEREO / VIDEO SYNC LED 11
4.7 SAP CARRIER ON LED 11
4.8 SAP CARRIER LEVEL SETTING 11
4.9 SAP AUDIO LEVEL; OK & HI LEDS 11
5.0 SPECIFICATIONS 12
6.0 AUDIO PERFORMANCE EVALUATION 14
7.0 TROUBLESHOOTING 14
7.1 COMMON SETUP ERRORS 14
7.2 TROUBLESHOOTING WITH A STEREO DECODER 14
7.2.1 USE YOUR EARS 15
7.3 TROUBLESHOOTING WITHOUT A STEREO DECODER 15
7.3.1 TROUBLESHOOTING WITH A SPECTRUM ANALYZER 15
7.3.2 TROUBLESHOOTING WITH AN OSCILLOSCOPE 16
8.0 INTERNAL SAP GENERATOR INSTALLATION 17
APPENDIX CONNECTION DRAWINGS 19

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1.0 QUICKSTART
This section is provided for those who want to skip directly to connecting the MTS-5 into
their system. At the minimum, please see the Connection Diagrams in the Appendix at the
rear of this manual, and read the remainder of this section (1.X).
1.1 Configure Video Modulator to accept BTSC Stereo in the format you wish to use.
Refer to Section 3.3.
1.2 Loop baseband video through the MTS-5 on its way to the video modulator. Refer to
Section 3.2.
1.3 Connect the output of the MTS-5 to your TV channel modulator (use either
baseband multiplex or 4.5 MHz). Refer to Section 3.3.
1.4 Connect Program Audio to the MTS-5. Refer to Section 3.1.
1.5 Connect AC Line Power.
1.6.1 If using Baseband Multiplex Stereo feed to audio modulator in video modulator,
adjust Aural Carrier Deviation at video modulator. Refer to Section 4.1.
1.6.2 If using 4.5 MHz feed to video modulator, adjust CARRIER LEVEL output of MTS-5.
Refer to Section 4.2.
1.7 Adjust AUDIO LEVELS at MTS-5. Refer to Section 4.4
2.0 INTRODUCTION TO THE MTS-5
The Leaming MTS-5 provides a space-efficient means of generating high-quality TV
audio in BTSC stereo format, and optionally, also in SAP (Second-Audio-Program)
format.
The MTS-5 generates the U.S. broadcast-standard BTSC format, includingdbx
companding. Left and Right baseband audio inputs are processed into a composite
multiplex stereo signal. This signal is available from the MTS-5 both at baseband
and on a 4.5 MHz carrier. Separate video sync input and 4.5 MHz audio carrier
output loops are standard.
The MTS-5 has dual stereo inputs. The second input may be used for local ad
insertion, or as an audio backup.
The MTS-5 includes automatic audio gain controls (AGC), which can significantly
reduce the program level variations that often occur when the program source
changes.
The MTS-5 displays audio program levels with dual peak-reading 10-segment LED
bargraphs, and AGC status with OK & HI LED indicators.

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A Second Audio Program (SAP) generator sub-board may be easily snapped onto
the main MTS-5 board; only a few internal jumpers need to be re-positioned on the
main board. No calibration is required, other than setting the SAP audio input level
from the front panel of the MTS-5. The optional SAP sub-board is also equipped
with AGC, and peak-level/AGC status indicators.
In addition, for those who may prefer an external SAP generator,a SAP carrier input
is provided on the MTS-5. The Leaming SAP-1 or SAP-2 can be powered by the
MTS-5.
A Bessel-null calibration test tone is built-in to ensure a simple and accurate setup
when the compositebaseband interface is used.
A thorough complement of front-panel switches, level controls, and LED indicators
facilitates use of the MTS-5's features.
3.0 INSTALLATION
Refer to the CONNECTIONS drawings at the end of this book for illustrations of how
the MTS-5 hooks to the other components in the system. Note that it is always
necessary for the video to loop through the MTS-5 in order to phase-lock the stereo
pilot to the horizontal sync of the video.
3.1 AUDIO INPUT
For signals from a balanced source, connect a shielded audio cable pair from the left
channel of your stereo audio program source to the left channel of Input "A" ("A
Audio In","LEFT") on the MTS-5. Run an additional shielded cable pair from the
right channel of your program source to the right "A" input ("A AUDIO IN","RIGHT").
Be sure that the + goes to the +, and the - goes to the -.
For signals from an unbalanced source, connect the high to the "+" and the shield to
the "-". Also, tie the "-" to the "G" (Ground) terminal if the two chassis are not
otherwise electrically grounded to each other.
NOTE:The screw-terminal strips located on the back panel of the MTS-5 may be
removed (unplugged) for ease in wiring, and detachment also facilitates reading
the pin identification on the rear label.
3.1.1 SECOND (B) AUDIO INPUT
"Input B" can be used for local ad insertion or backup audio. The B input is wired in
the same procedure as that listed in Section 3.1, with the exception that it is wired
into Input B (B Audio In) on the back of the MTS-5, rather than Input A. See Section
4.3 for information regarding the selection of A/B inputs, and the optional use of the
main (stereo) audio's "B" input to also feed an alternate signal to the optional internal
SAP generator.

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3.2 VIDEO SYNC IN CONNECTIONS
The MTS-5's "VIDEO LOOP IN" must be connected tobaseband video
(unscrambled), to permit the stereo pilot within the MTS-5 to frequency-lock to it.
The "VIDEO LOOP OUT" is to be connected as noted in 3.3.1, 3.3.2, or 3.3.3,
depending on the format selected.
3.3 COMPOSITE BASEBAND OR 4.5 MHz FEED TO TV MODULATOR
TV channel modulators generally accept BTSC stereo in either of two common
formats:
1) As a Composite (Multiplexed) Baseband "audio" or
2) On a 4.5 MHz subcarrier.
The MTS-5 provides both formats simultaneously. Either format produces
satisfactory results. The selection of which format to use is dependent on what your
TV modulator will accept, and which has been adopted as the preferred method in
your system.
Refer to connection diagrams D2 through D4 (located at the rear of this manual)
3.3.1 BASEBAND STEREO MULTIPLEX TO TV MODULATOR
This method uses the audio modulator built into the video modulator; the 4.5 MHz
modulator in the MTS-5 is not used. First, verify that your TV modulator is capable
of accepting abaseband multiplex BTSC audio signal.
NOTE:All video modulators require configuration to accept a BTSC stereo multiplex
signal, instead of mono audio. In most cases, this may be accomplished by re-
positioning a few switches or jump-jacks in the modulator. Specifically, the 75 µS
pre-emphasis, and any audio limiting, if present, must be removed. The
modulator must have a wide "audio" bandwidth (flat through approx. 110kHz).
Contact your TV modulator manufacturer for configuration instructions.
Once your TV modulator has been properly configured to accept BTSC stereo as a
baseband multiplex signal, refer to diagram D2 (at the rear of this manual) for an
illustration of the external hookup:
Connect the "VIDEO SYNC IN" loop "OUT" on the MTS-5 to the "Video In" on your
TV modulator.
Then connect a shielded audio cable from the "BTSC MULTIPLEX OUT" on the
MTS-5 to the "Audio In" on the TV modulator.
NOTE:The BTSC MULTIPLEX OUTPUT of the MTS-5 is not balanced, When driving a
balanced load, the + (Red) goes to the +, any one of the MTS-5's G (Chassis

10 April 2002 MTS-5 PAGE 6of 21
Ground) terminals goes to - (Black), and another G (chassis ground) terminal
goes to the shield (drain) wire.
For signals to an unbalanced load, connect the + (red, high) to the +, and the shield
(and Black, if present) to "G" (Ground) terminals at both the MTS-5 and the video
modulator.
NOTE:If you are using the 4.5 MHz (Audio Carrier) output of the MTS-5, instead of the
baseband multiplex output of the MTS-5, there is no need to connect anything to
the "Audio In" of the video modulator or the "BTSC MULTIPLEX OUT" on the
MTS-5.
3.3.2 4.5 MHz AUDIO CARRIER WITH VIDEO
If the TV modulator you are using accepts the 4.5 MHz audio carrier on the same
cable as video, rather than on a separate cable from video, refer to diagram D3:
Connect a jumper cable from the "VIDEO SYNC OUT" of the MTS-5 to the "AUDIO
CARRIER IN" of the MTS-5.
Connect another cable from the "AUDIO CARRIER OUT" on the MTS-5 to the
"Video plus 4.5 MHz Input" on your TV modulator.
NOTE:If you are using the BTSC MULTIPLEX OUT (baseband) of the MTS-5, instead of
the AUDIO CARRIER OUT (4.5 MHz) of the MTS-5, there is no need to connect
anything to the AUDIO CARRIER OUT of the MTS-5.
3.3.3 4.5 MHz AUDIO CARRIER SEPARATE FROM VIDEO
If the TV modulator you are using requires separate video and 4.5 MHz inputs, refer
to diagram D4:
Connect one cable from the "VIDEO SYNC OUT" connector on the MTS-5 to the
"Video In" on the TV modulator.
Connect another cable from the "AUDIO CARRIER OUT" on the MTS-5 to the
"Audio Carrier In" on the TV channel modulator. Then install a 75 ohm terminating
resistor on the "AUDIO CARRIER IN" connector on the MTS-5.
3.4 VIDEO SCRAMBLING
Because most video scramblers work at TV I.F. (45.75 & 41.25 MHz), the stereo
connections are generally unaffected. However, if there is any possibility that the
video is scrambled atbaseband, loop the unscrambled video through the MTS-5
before the scrambler; the MTS-5 will not function properly if it is receiving sync-
suppressed baseband video (i.e. the stereo pilot cannot sync tobaseband-
scrambled video).

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4.0 OPERATION
4.1 SETTING THE AUDIO CARRIER DEVIATION
If you are using the 4.5 MHz Audio Carrier Output of the MTS-5, its deviation has
been calibrated at the factory; it is not field-adjustable. Skip to Section 4.2.
If you are using the composite baseband multiplex output of the MTS-5, the aural
carrier deviation must be accurately set at the TV channel modulator. (Otherwise,
stereo channel separation will be less than optimum.)
The TEST position of the "TEST MONO STEREO" switch (located on the MTS-5's
front panel) activates a test tone, and shuts off the audio inputs, to facilitate setting
the deviation of an external audio modulator.
The most convenient and accurate way of verifying correct deviation is to use the
test tone and a spectrum analyzer to observe the firstBessel-null of the carrier.
As alternate methods, you may use either the meter or the peak modulation
(±25 kHz) light on your TV modulator.
NOTE: If a video scrambler is being used in conjunction with the BTSC stereo generator,
to avoid possible interaction with the calibration tone, the scrambler should be off
or in the bypass mode while setting the audio deviation.
4.1.1 SPECTRUM ANALYZER & TEST TONE METHODS:
Move the "TEST MONO STEREO" switch to the "TEST" (left) position. Both the "A"
& "B" input lightswill extinguish. Using a spectrum analyzer, look at the audio
carrier from your TV modulator. (For a clear picture, 20 kHz to 50 kHz resolution per
division is suggested.) Using the front-panel deviation control on the TV modulator,
null the carrier (to thefirst Bessel-null; see diagram 4-1).
To verify that the deviation is adjusted correctly, check the amplitude of the
15.734 kHz stereo pilotsidebands relative to the audio carrier. To do so, set the test
switch to the "STEREO" (right) position and, at reduced audio input levels, look at
the audio carrier and bothsidebands using a spectrum analyzer (onesideband
should be 15.734 kHz above the audio carrier and anothersideband should be
15.734 kHz lower than the audio carrier). If the deviation is properly adjusted, the
two sidebands should be approximately 16 dB down from the carrier (Refer to
diagram 4-2). If they are not, after repeating the Bessel Null procedure, repair and
calibration of the equipment is needed.

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Figure 4-1A
Correct Bessel-null Figure 4-1B Incorrect Bessel-null
Figure 4-2
Main Audio Carrier with
Pilot Carrier Sidebands
Horizontal:
20 kHz/div
Vertical:
10 dB/div
(All Views)
4.1.2 USING THE METER OR PEAK FLASHER ON THE TV MODULATOR:
If you are using the meter on your TV modulator to set the deviation, move the "TEST
MONO STEREO" switch to "TEST" (left position). Increase the Aural Carrier
Deviation (not Level) until the "±25 kHz" or "100%" or "0 VU" light on the TV
modulator comes on. Then, back it off until the light "just" goes off.
NOTE:If SAP or scrambling is being used, be sure that it is off or in the bypass mode
while setting the deviation.
OPERATIONAL NOTE:The audio peak flasher on the TV modulator may flash during
normal stereo operation, and more so if SAP is also present.
4.2 AUDIO CARRIER LEVEL ADJUSTMENT
Whenusing the 4.5 MHz audio carrier output from the MTS-5, the carrier level must
be adjusted, generally both at the MTS-5 and at the TV modulator. In a typical case,
such as when an MTS-5 feeds a Scientific Atlanta 6350, the audio carrier level is
adjusted first at the MTS-5 while monitoring the TV channel output of the SA6350
with a spectrum analyzer: Increase the carrier level at the MTS-5 until the output of
the 6350 ceases to increase, indicating that the 6350 has achieved limiting. This is
the optimum drive level to the 6350; less drive results in noisier audio, and more drive
may splatter the audio into the video. Then adjust the Aural Carrier Level on the
6350 to set it at the desired output level, which is usually 15 dB below the
(unmodulated) video carrier.
4.3 "A"/"B" AUDIO INPUTS
LEDS indicate which input is active, as selected remotely, or by the front-panel switch
(which can enable or override the remote control). If power is applied, and neither
"A" nor "B" is illuminated, the MTS-5's TEST/MONO/STEREO switch is in Test mode.

10 April 2002 MTS-5 PAGE 9of 21
4.3.1 LOCAL & REMOTE AUDIO INPUT SELECTION:
Selection of "A" or "B" inputs, or switching the optional SAP carrier on, may be
accomplished either locally, or remotely. The "A" and "B" positions of the front panel
switch will override remote A/B control.
By grounding a line connected to the A/B terminal on the rear panel of the MTS-5, if
the front-panel switch is in the center "REM" position, the "B" inputs will be selected.
The "REM" terminal is normally pulled to +5 volts by a resistor; any switch, relay, or
appropriate logic device capable of sinking 0.5 mA and pulling the line to within a volt
of ground may be used.
4.3.2 INTERNAL SAP "B" INPUT:
The internal SAP generator is normally connected to the SAP audio program input at
all times. This is generally not a problem, because much of the equipment which can
insert local commercials can switch both the mono SAP audio and the stereo
program audio. If it cannot handle all three channels (Left, Right, & SAP), the
MTS-5's A/B switch can handle the stereo, leaving the commercial insert equipment
to handle the mono SAP program switch-over.
In the event that it is desired to switch the SAP audio to the same signal as the stereo
channel's "B" signal, and at the same time as the stereo channel switches to the "B"
channel, a jump-jack internal to the MTS-5 can be positioned to accomplish this.
That location is labeled P725, and it is on the main MTS-5 board, just in front of the
SAP sub-board. Then, when the main (stereo) channel's "B" input is selected (either
locally or remotely), that same stereo audio program will also be delivered (in mono)
to the SAP channel. The "B" SAP program level is pre-calibrated; if the stereo level
is correct, the SAP level will be correct.
If no jump-jack is installed on P725, the internalSAP's audio is always straight-
through (unswitched).
4.4 STEREO AUDIO LEVELS and AGC CONSIDERATIONS
The MTS-5 is furnished with two sets of level controls on the front panel: "A LEVEL"
"LEFT" & "RIGHT" and "B LEVEL" "LEFT" & "RIGHT". Stereo audio program levels
are monitored with dual peak-reading LEDbargraph meters.
While listening to the audio program, with the audio AGC OFF, use a small flat-blade
screwdriver thru the front-panel access holes to adjust the corresponding level
controls so that both the left and the right meters read approximately 0 VU (regular
flashes of the yellow LEDs on program peaks). The red +3 VU LEDs may flash
briefly with very loud program peaks.

10 April 2002 MTS-5 PAGE 10 of 21
NOTE:It is recommended that the program be listened to while adjusting the audio level
controls, to ascertain that the peak indicators are flashing only on material that is
intended to be loud.
If desired, the audio AGC may be switched on after setting the audio levels. There
should be no significant level change during normal program, but any over-
modulation will be quickly reduced (within milliseconds); conversely, prolonged
under-modulation will be gradually increased. The under-modulation correction is 1:2
dB; that is, if the 15-second time-averaged peak input level drops 10 dB, the peak
output level will drop only 5 dB. The maximum under-modulation gain increase is
limited to approximately 12 dB, in order to avoid increasing background noise
excessively.
4.5 AUDIO AGC OK & HI INDICATORS:
When the audio AGC is on, the OK LED is illuminated whenever the incoming audio
program level is within the normal range of the AGC, where the AGC can "silently"
maintain good program dynamics.
The OK LED may extinguish if the program level remains very low for approx. 15
seconds or more. If the OK LED extinguishes regularly, listen to the audio program
to determine whether or not it is intended to be very quiet. If not, re-adjust the
appropriate front-panel potentiometers so that the OK LED, but not the HI LED, is
usually illuminated.
If the incoming program level increases substantially from the initial setting, the HI
LED will become brighter and remain steadily illuminated, and the OK LED will
extinguish, indicating that the audio AGC is maintaining a relatively constant peak
output level. If the HI LED is on steadily, or for a significant time, the input level
should be manually reduced somewhat with the appropriate front-panel
potentiometers, in order to maintain optimum program dynamics.
It is not essential to switch the AGC off to make minor adjustments of the level
controls; the VU meters give a continual indication of the outgoing audio levels, and
the OK & HI LEDs give a long-term indication of how hard the AGC is working. In
general, the OK LED should always be illuminated, unless there has been a 15-
second period of silence (signal peak levels over 20 dB below the recent peak
levels), in which case the OK LED will extinguish. At that time, the AGC will return to
its standby gain setting, awaiting the arrival of program material, at which time it will
automatically re-activate.
The HI LED should flash occasionally and very briefly on exceptionally loud program
peaks. The HI LED should not normally remain on for more than a few milliseconds.
If it does remain illuminated, the program levels should probably be manually
reduced, to optimize theAGC's range. (There may be a several-second delay before
extinguishing the OK and HI indicators after the incoming program level is reduced,
but there is essentially no delay before illumination as the program level is
increased.)