RACK MOUNTING
Adequate ventilation is very important in multichannel
installations. Units should be spaced apart by at least
one panel height wherever possible, and some air
movement is advisable in enclosed rack cabinets.
Excessive heat will shorten component life and modulator
performance will be degraded without proper cooling.
USE WITH A STEREO ENCODER
An external BTSC stereo encoder may be used with the
VM2551. To sett the VM2551 for a flat audio response
that will accept the BTSC composite stereo input - remove
the top cover of the VM2551. Observing the PCB that
contians the Audio, Video, A/V Ratio, and other compo-
nents, locate the small slide switch - SW2. Set switch
SW2 to the Pre-emphasis OFF position. The factory
default setting is Pre-emphasis ON - for mono operation.
CONNECTIONS AND CONTROLS
All connections to and from the VM2551 are made
through the rear panel. Additional channels can be
added by using additional VM2551 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 to 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 Level'
and 'A/V Ratio' controls are used respectively to make
these adjustments. If an output level of less than
+40 dBmV is required, add an attenuator of the
appropriate value to the modulator output.
6 Installation
