Drake VM2551A Agile Modulator – 550 MHz - Manual (Page 4)

4 Table of Contents / Description / Specifications
2 Caution Statements
2 Important Safety Instructions
4 Table of Contents / Description / Specifications
5 Front / Rear Panel Controls and Indicators
6 Operation
7 Adjustments
8
10
Channel Assignments
11
Service / If You Need to Call For Help
Warranty
SPECIFICATIONS
TABLE OF CONTENTS
A manual or auto-switching alternate IF input, labeled E AS input,
is provided for connection of an Emergency Alert System 44 MHz
IF signal. When the EAS IF signal appears at the EAS input, the
main video and audio modulated IF is replaced by the EAS input
signal.
The EAS/Alternate IF feature allows a choice between manual
and automatic selection of the EAS/ALT IF input signal. This
is done through a 3 position terminal strip on the rear of the unit.
In the manual mode the EAS/ALT IF feature is activated by a contact
closure switch, which completes a ground connection. In the
automatic mode, two positions on the terminal strip are jumpered
together enabling an automatic detection circuit in the unit. When an
EAS/ALT IF signal is routed to the EAS/ALT port the unit automatically
switches to that alternate signal.
DESCRIPTION
The R.L. Drake VM2551A Agile Video Modulator is a high quality,
vestigial sideband unit with synthesized visual and aural carriers.
It is designed to accept NTSC video and audio baseband signals from
a satellite receiver or similar equipment. Front panel video and audio
level controls with accompanying modulation indicators permit easy
setup of the proper modulation levels. The A/V ratio and RF output level
controls are also provided on the front panel. A rear panel EAS alternate
IF input is also provided.
Synthesized operation provides complete frequency agility, allowing
front panel selection of any standard CATV channel from 2 to 78. FCC-
required offsets for aeronautical channels are automatically provided for
each channel that requires an offset. For special applications, IRC or HRC
CATV frequencies or off-air broadcast frequencies can be selected from
the front panel.
A high quality IF SAW filter with FCC pre-distortion eliminates adjacent
channel interference and provides optimum delay characteristics.
VIDEO INPUT
Connector: F-Type (Female)
Impedance: 75 ohms
Return Loss: 18 dB
Video Input Level: 0.7 volt Peak-to-Peak
Signal-to-Noise Ratio: 58 dB
Differential Gain: 2.0%
Differential Phase: 1.0 degree
Over-modulation Indicator: 87 to 92%
L/C Delay: Per FCC Requirements
RF OUTPUT
Connector: F-Type (Female)
Impedance: 75 ohms
Return Loss: 12 dB
Channel Modes: CATV (STD, IRC, HRC), UHF, VHF
Power Level Range: +50 to +60 dBmV (in 0.2 dB increments)
Video Flatness: fv-0.5 to fv+4.2 MHz: 1.5 dB p/v
Carrier-to-Noise: -63 dB
Broadband Noise: -77 dBc
Spurious Outputs: -63 dBc
Aural/Visual Carrier Ratio: -15 ± 5 dB
GENERAL
AC Power: 117 VAC ± 10%, 60 Hz, 23 Watt max
Fuse: 0.4A Type T 250 V
Temperature Range: 32° to 122° F
Size: 19.0” W x 14.25” D x 1.75” H
Weight: 7 lbs.
MONO AUDIO
Connector: RCA-Type
Input Impedance: Greater than 10k ohms, unbalanced
Input Level: 0.5 to 4.0 volt Peak-to-Peak
Frequency Range: 50 Hz to 15 kHz
Frequency Response: ± 0.5 dB
Total Harmonic Distortion: 1% @ 25 kHz deviation
Signal-to-Noise Ration: 59 dB
Over-modulation Threshold: 25 ± 2 kHz peak deviation
IF
Input/Output Connector: F-Type (Female)
Aural Frequency: 41.25 MHz
Visual Frequency: 45.75 MHz
COMPOSITE IF
Aural: +20 dBmV
Visual: +35 dBmV
Input/Output Impedance: 75 ohms
Input/Output Return Loss: 16/15 dB
EAS / ALTERNATIVE IF
Connector: F-Type (Female)
Input Level: +30 dBmV @ 45.75 MHz
Switch Isolation: Greater than 60 dB
VM2551A VIDEO MODULATOR