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VMD860AG VIDEO MODULATOR

This instruction manual also is applicable to the

VMD860AS, VMR860AG, and VMR860AS.

The AS models include a built-in BTSC stereo

audio encoder to provide stereo audio.

The VMR models are electrically identical to the

VMD units except that they are designed for

19" rack mounting.

In this manual, only the VMD860AG model is

discussed except where there are differ-

ences. Any differences will be explained.

The R.L. Drake VMD860AG family of Audio-

Video Modulators includes high quality, vestigial

sideband units with synthesized visual and

aural carriers. The frequency agile units allow

front panel pushwheel switch selection of

standard CATV channels 2 through 135, CATV

subband channels, T7 through T14, or VHF/

UHF TV channels 2 through 69. Additionally,

IRC or HRC CATV channel plans may be

selected after moving an internal jumper.

Aeronautical channels are offset positive with

a tolerance of ±5 kHz as required by FCC

rules.

The heterodyne conversion system, in

conjunction with the use of a SAW filter,

ensures optimum vestigial selectivity for

adjacent channel headends.

Broadband noise and in-channel noise are

reduced to a very low levels to provide

excellent performance in multichannel CATV

headend environments.

® is a registered trademark of the R.L. Drake Company

The modulators are designed to accept any

standard audio/video source such as NTSC

video and audio baseband signals from a

satellite receiver, TV camera, videotape

recorder, TV demodulator, or similar signal

source. The VMD860AS and VMR860AS can

accept stereo audio inputs and produce a

BTSC stereo audio signal.

When stereo audio is required, the preferred

method of providing a BTSC stereo signal is to

use the VMD860AS or VMR860AS model. No

special setup or test equipment is required.

Also, field-defeatable audio pre-emphasis in

the AG models allows transmission of BTSC

encoded baseband stereo audio signals from

an external BTSC stereo encoder, such as the

Drake MMTS20. Optimum performance requires

proper test equipment for setup with external

BTSC encoders.

The AG models will accept either mono or

stereo inputs and output a mono audio signal

with left and right inputs being summed in the

modulator.

The modulators are designed to accept

standard (negative sync) polarity video at 0.6

to 1.5 Vp-p level. All level controls are located

on the front panel for ease of operation. Audio

and video overmodulation indicators are

provided. Output level is +45 dBmV and is

adjustable downward.

FCC predistortion is provided in the video IF.

P/N: 3852411E-04-2007

Printed in the U.S.A.

FRONT PANEL CONTROLS and INDICATORS

F1 - POWER/Error Indicator

Lights when the unit is connected to the

required source of DC power via the rear panel

DC INPUT connector. A flashing condition

indicates an invalid channel setting or other

conditions that would cause the unit to operate

on an invalid channel. The RF output is

switched off for flashing (ERROR) conditions.

F2 - VIDEO Level Control

The setting of this screwdriver adjustment

determines the video modulation level.

Clockwise rotation increases the

modulation depth.

F3 - Video OVER MODULATION LED

With a video input applied, adjust (F2) until this

indicator just illuminates, then set just below

this point.

F4 - AUDIO Level Control

The setting of this screwdriver adjustment

determines the aural carrier deviation. Clock-

wise rotation increases the carrier deviation.

F5 - Audio OVER MODULATION LED

With audio applied, adjust (F4) until this

indicator just illuminates on peaks.

F6 - A/V RATIO Control

This screwdriver adjustment varies the level of

the aural carrier over a range from 12 to

20 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.

F5 F6

Figure 1

F7 -T CHANNEL Switch

Set this switch to the "T" channel setting to

enable "T" channel coverage. Use the Channel

Number switch (F9) to select 7 - 14. For normal

CATV or broadcast TV channels, this switch

must be set to the right to enable selection by

the mode switch (F8).

F8 - Mode Switch

Sets the type of channel, CATV or Broadcast

TV ("BCTV"). This switch does not function if

switch (F7) is in the "T" channel position. The

last position of the switch ("+100") sets a

leading "1" for CATV channels 100 through 125.

See Item (F9) for setting the channel number.

Example 1:

Setting for CATV

channel "125"-

Example 2:

Setting for CATV

channel "25"-

F9 - CHANNEL Number Switch

Sets the desired operating channel for standard

CATV channels 02 through 135, "T" channels

T7 through T14, or Broadcast TV channels 02

through 69. See Item (F8) which sets the type

of channel (CATV or Broadcast TV) and sets

the leading "1" for CATV channels 100 through

125.

F10 - RF OUTPUT LEVEL

This screwdriver adjustment permits decreasing

the RF output level a minimum of 10 dB as the

control is rotated counterclockwise. Set the

control for a desired output level.

F10

CATV +100

CATV

BCTV

T CHANNELS

CHANNEL

CATV +100

CATV

BCTV

T CHANNELS

CHANNEL