DRAKE VM1550, Instruction Manual

4     Table of Contents / General Description

Caution Statements

Important Safety Instructions

Table of Contents / General Description

Specifications

Front Panel Controls and Indicators

Rear Panel Connections

2

3

4

5

6

7

Installation

Frequency Allocation Chart

Internal Jumper Selection

Notes

Service Information /
If You Need To Call For Help

Warranty

8

9

10

11

12

13

TABLE OF CONTENTS

GENERAL DESCRIPTION

The R.L Drake VM1550 Video Modulator is a high quality
vestigial sideband heterodyne audio/video modulator that
provides a modulated visual and aural RF carrier output
on VHF channels,  2-13; Midband, A-I; Superband, J-W;
or Hyperband, AA-HH. Consult factory for custom
channels.  All aeronautical channels are offset positive
with a tolerance of ±5 kHz as required by FCC rules.  The
VM1550 is designed to accept video and audio baseband
signals from a satellite receiver, TV camera, video tape
recorder, TV modulator or similar equipment.  The
heterodyne conversion system, in conjunction with the
use of a SAW filter, insures optimum vestigial selectivity
for adjacent channel headends.

IF loop-thru capability in the VM1550 supplies a padded
IF output prior to channel conversion.  This feature
provides the capability to replace the standard internally
generated IF output with an alternate source of composite
IF, or allows insertion of IF scrambling equipment.

VM1550 VIDEO MODULATOR

POWER

OVER

MODULATION

RF  LEVEL

A U D I O   L E V E L

V I D E O   L E V E L

A / V  R A T I O

CHANNEL

The modulator accepts standard (sync negative) polarity
video at a 0.7 -2.5 Vpp level.  All level controls and
modulation indicators are located on the front panel for
ease of operation.

Field-defeatable audio pre-emphasis enables
transmission of BTSC encoded standard baseband stereo
audio signals.