DRAKE MMTS20 Manual - Página 4

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4
INSTALLATION
CONNECTIONS AND CONTROLS
All connections to and from each modulator
are made through the rear panel. Figure 3
illustrates an installation with (11) modulator
units combined through a passive signal
combiner. Additional channels can be added
by using additional fixed channel or agile type
modulators and either multi-port combiners or
combinations of two-port combiners.
INSTALLATION NOTES
Level adjustment provides optimum
performance in multichannel installations.
The modulator outputs should be checked
periodically with a spectrum analyzer to
VIDEO INPUT
MMTS20
AUDIO IN
To Video Input
STEREO
RIGHT LEFT
ENCODER
of MMTS20
AC POWER
DC POWER
CORD
CABLE
RF COMBINER
maintain a ±1 dB variation of adjacent channel
carriers. Aural/Visual (A/V) ratios should be
held to -15 dB or less. The output 'RF' and 'A/V
(Ratio)' controls are used respectively to make
these adjustments.
RACK MOUNTING
Adequate ventilation is very important in
multichannel installations. Some air movement
is mandatory in enclosed rack cabinets.
Excessive heat will shorten component life and
modulator performance will be degraded without
proper cooling.
To Video Input of
Video Modulator
MODULATOR UNIT
(Fixed channel and/or Agile type -
audio response set for "Flat")
SYSTEM OUT
Figure 3
INSTALLATION - AUDIO LEVEL SETTINGS
METHOD 1:
Connect the MMTS20, Audio/Video Modulator,
compatible DC power source, video source
signal and test equipment as shown.
Video Source
Video Input
Loop-Through
Audio
Cable
Composite
Audio Out
DC Input
DC Input
Left Audio In
Right Audio In
MMTS20
REAR PANEL
MODULATOR
1) Set the 'Test Tone' switch on the front panel
of the MMTS20 to the 'ON' position.
PILOT
LOCK
ON
TEST
TONE
OFF
2) Using the connected spectrum analyzer, tune
the aural carrier to the center of the screen.
Spectrum Analyzer Settings:
SPAN: 100 kHz.
Res BW: 1 kHz.
SWEEP: 300 mSec.
VBW: 1 kHz.
Aural Carrier Centered
Make certain that the audio response of the A/V
modulator is set for 'FLAT' (pre-emphasis
defeated).
Coaxial Cable
A/V
3) Adjust the 'Audio Level' control on the front
panel of the connected A/V modulator for a
setting that nulls the aural carrier. If more than
one null is found, use the lowest audio gain
setting that produces a null of the aural carrier.
MODULATOR
AUDIO
VIDEO
Aural Carrier Null
5
SPECTRUM
ANALYZER