DRAKE VM2551 Gebrauchsanweisung - Seite 6

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Installation

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.

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.