DRAKE VMM 860 Buku Petunjuk - Halaman 2

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2 FRONT PANEL DESCRIPTION

Figure 1

F1 - AUDIO Level Control

The setting of this screwdriver adjustment

determines the peak aural carrier deviation.

Clockwise rotation increases the carrier

deviation.

F2 - VIDEO Level Control

The setting of this screwdriver adjustment

determines the video modulation level.

Clockwise rotation increases the modulation

depth.

F3 - POWER Indicator

Lights when the unit is connected to the

required source of DC power via the rear panel

DC INPUT connector.

F4 - A/V Ratio Control

This screwdriver adjustment varies the level of

the aural carrier over a range from 12 to 19 dB

below the visual carrier. The aural carrier

should be adjusted to approximately 15 dB

below the visual carrier (normal operation).

Clockwise rotation increases the aural carrier

level and thus decreases the A/V ratio.

F5 - "CH#" (Channel)

The modulator is factory aligned to the

channel number indicated.

F6 - RF Output Level

This screwdriver adjustment permits

decreasing the RF output level approximately

12 dB below its specified output level as the

control is rotated counterclockwise. The

maximum output level is set with the

adjustment fully clockwise.

REAR PANEL DESCRIPTION

+5V

+12V

GND

Figure 2

R1 - VIDEO INPUT Connector

This is the baseband video input to the IF

circuits. This input accepts baseband input

thru 4.2 MHz video at levels from 0.7 Vp-p to

1.5 Vp-p.

R2 - AUDIO INPUT Connector

This is an unbalanced audio input to the IF

circuits. This "RCA" (phono) connector input

accepts baseband thru 15 kHz audio at a

nominal level of 250 mV RMS (approximately

0 dBm). NOTE: An externally accessible test

point jumper defeats the audio pre-emphasis

for stereo capability.

R3 - DC INPUT Connector

This 3-pin connector (Male) accepts the

appropriate mating DC power cable. Observe

proper orientation and wiring.

R4 - RF OUTPUT Connector

This is the modulator output.

INTERNAL JUMPER

AUDIO PRE-EMPHASIS

(On) MONO

AUDIO PRE-EMPHASIS

(Off) STEREO w/MMTS20

INSTALLATION

CONNECTIONS AND CONTROLS

All connections to and from each modulator

are made through the rear panel. Figure 3

illustrates an installation with 12 modulator units

combined through a passive signal combiner.

Additional channels can be added by using

additional VMM 600 or VMM 860 modulators

and

either

multi-por t

combiners

combinations of two-port combiners.

INSTALLATION NOTES

Level

adjustment

provides

optimum

performance in multi-channel installations. The

modulator outputs should be checked

periodically with a spectrum analyzer to

maintain a ±1 dB variation of adjacent

channel carriers.

AUDIO INPUTS

AC POWER

CORD

VIDEO INPUTS

DC POWER

CABLE

RF COMBINER

R.L. DRAKE COMPANY

230 INDUSTRIAL DRIVE

FRANKLIN, OHIO 45005 U.S.A.

CUSTOMER SERVICE AND PARTS TELEPHONE:

+1 (937) 746-6990

+1 (937) 806-1576

WORLD WIDE WEB SITE: http://www.rldrake.com

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

multi-channel 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.

VMM 600's/VMM 860's

SYSTEM OUT

Figure 3

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