Drake 300VMF+ Fixed Modulator User Manual

300VMF+

Commercial Video Modulator

(For use in NTSC systems)

INSTRUCTION MANUAL

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

© Copyright 2013 R. L. Drake Holdings, LLC Printed in Taiwan.

Rev: 20130322
10037xx

2 Caution Statements

IMPORTANT SAFEGUARDS

This symbol is intended to alert the user to the presence of non-insulated
“dangerous voltage” within the product’s enclosure, that may be of suffi cient

magnitude to constitute a risk of electric shock to persons.

ing and maintenance (servicing) instructions in the literature accompanying

WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK,

CAUTION: Do not attempt to service this product yourself as opening or removing covers may

ATTENTION: POUR PREVENIR LES CHOCS ELECTRIQUES, NE PAS UTILISER CETTE

VERT.

This symbol is intended to alert the user to the presence of important operat­the appliance.

CAUTION

TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK, DO NOT EXPOSE THIS
APPLIANCE TO RAIN OR MOISTURE

CAUTION

TO REDUCE THE RISK OF ELECTRIC SHOCK,
DO NOT REMOVE COVER (OR BACK)
NO USER SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED PERSONNEL.

DO NOT EXPOSE THIS APPARATUS TO RAIN OR MOISTURE.

expose you to dangerous voltage or other hazards. Refer all servicing to qualifi ed

service personnel.

FICHE POLARISEE AVEC UN PROLONGATEUR, UNE PRISE DE COURANT
OU UNE AUTRE SORTIE DE COURANT, SAUF SI LES LAMES PEUVENT
ETRE INSEREES A FOND SANS EN LAISSER AUCUNE PARTIE A DECOU-

IMPORTANT SAFETY INSTRUCTIONS

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.

8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (includ-

ing amplifi ers) that produce heat.

9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding type plug has two blades and a third grounding prong. The

wide blade or the third prong are provided for your safety. If the provided plug does not fi t into your outlet, con-

sult an electrician for replacement of the obsolete outlet.

10. Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles,
and the point where they exit from the apparatus.

11. Only use attachments/accessories specifi ed by the manufacturer.

12. Use only with the cart, stand, tripod, bracket, or table specifi ed by the manufacturer, or sold with the

apparatus. When a cart is used, use caution when moving the cart/apparatus combination to avoid injury from
tip-over.

13. Unplug the apparatus during lightning storms or when unused for long periods of time.

14. Refer all servicing to qualifi ed service personnel. Servicing is required when the apparatus has been

damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have
fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or
has been dropped.

Table of Contents/Description/Specifi cations 3

TABLE OF CONTENTS
2 Caution Statements 5 Rear Panel Connections and Internal Jumper
2 Important Safety Instructions 6 Installation
3 Table of Contents / General Description 7 Frequency Allocation Charts
3 Specifi cations 8 Service / If You Need To Call For Help
4 Front Panel Controls, Indicators, and 9 Warranty
Connections

DESCRIPTION

The DRACOM 300VMF+ Video Modulator is a vestigial sideband heterodyne audio/video modulator that provides a
modulated visual and aural RF carrier output on any single EIA standard channel from channel 2 through channel 78 plus
channels 95 to 99. This range covers 54 through 552 MHz. Consult factory for custom channels. All aeronautical chan­nels are offset positive with a tolerance of ±5 kHz as required by FCC rules. The 300VMF+ is designed to accept video
and audio baseband signals from a satellite receiver, TV camera, video tape recorder, TV demodulator or similar equip­ment. The heterodyne conversion system, in conjunction with the use of a SAW fi lter, insures optimum vestigial selectivity
for adjacent channel headends. The modulator accepts standard (sync negative) polarity video at a 0.7 -1.5 Vpp level. All
level controls are located on the front panel for ease of operation.

SPECIFICATIONS

RF

Frequency Range:

Channels Available:

FCC Frequency

Offsets:

Output Level:

Output Impedence:

Output Test:

A/V Ratio:

Frequency Stability,

Visual:

Aural Intercarrier

Frequency:

Spurious Outputs:

In-Channel C/N:

Broadband Noise:

54 - 552 MHz.

Factory-ordered for a single channel:

EIA CATV channels 2 to 78 and 95 to 99.

All aeronautical channels offset positive
with a tolerance of ±5 kHz.
+55 dBmV, (typically adjustable from +43
to +55 dBmV).
75 OHMS, return loss of 14 dB, nominal.

-30 dB, ±3 dB (referenced to
RF OUTPUT level).
Audio Carrier -20 to -12 dB referenced to
video carrier, adjustable.

Within ±10 kHz of assigned channel
frequency; ±5 kHz on FCC
offset channels.

4.5 MHz, ±5 kHz.

-60 dBc minimum, measured at -15 dB A/V
ratio and with modulator output level of
+55 dBmV.
Better than 60 dB.

-95 dBc @ ±30 MHz or
greater spacings. (Specifi ed levels are
referenced to the video carrier and
measured in a 4 MHz bandwidth).

VIDEO

Input level for 87.5%

Modulation:

Input Impedance:

Frequency Response:

Video S/N:

L/C Delay:

Differential Gain:

Differential Phase:

AUDIO

Input Level for

25 kHz Peak Deviation:

Input Impedance:

Pre-emphasis:

Frequency Response:

4.5 MHz Intercarrier Stability:
Total Harmonic Distortion:

Hum and Noise:

GENERAL

Modulator Power

Requirement:

Auxiliary AC Outlet:

Total AC Power Input:

Operating Temperature

Range:

Size:

Weight:

Connectors:

1 Vp-p ±3 dB, manual gain adjust with
front panel control.
75 Ohms, return loss of 18 dB
minimum.
Flat ±2 dB from 30 Hz to 4.2 MHz.
60 dB, luminance weighted.
Within 50 nSec of 0 nSec L/C delay
(complies with FCC rules, 76.605).
Less than ±5% (10 to 90% APL).
Less than ±5 degrees (10 to 90% APL).

175 mV rms minimum. Manual gain
adjustment with front panel control.
10K Ohms, unbalanced.
75 mSec.(fl at by moving internal jumper)
40 Hz to 15 kHz, ±1.5 dB, referenced to
75 mSec pre-emphasis curve.
Within ±5 kHz, 00 C to +500 C.

1.5% maximum.

-60 dB minimum, referenced
to 25 kHz peak deviation.

115 VAC ±10%, 60Hz, 10 Watts.
Nominal 120 VAC, 600 Watts, maximum.
Nominal 120 VAC 60 Hz,
610 Watts, maximum.

0 C to +50 C, ambient.
19” W x 1.75” H x 4.0” D.

3.6 lbs.
Video input, Audio input, RF output, and
Monitor output are all type F.

4 Front Panel Description

F1 F2 F3 F4 F5 F6 F7

F1 - POWER Indicator

Lights when the unit is connected to a source of AC
power.

F2 - OUTPUT TEST Connector

Provides a reduced level sample of the RF output signal.
The level at this connector is approximately 30 dB lower in
level than the RF OUTPUT signal. It is used to monitor
the active signal without affecting the level or quality of the
RF output signal.

F3 - CHANNEL Designation

The label indicates the fi xed channel output for your
particular model. The 300VMF+ is capable of fi xed

channel output (factory tuned) within the following
ranges: Channel 2 through 78 and 95 through 99.

F4 - RF OUTPUT LEVEL

This screwdriver adjustment permits decreasing the RF

output level a minimum of 12 dB below its specifi ed

output level as the control is rotated counterclockwise.
The maximum output level of +55 dBmV is set with the
adjustment approximately fully clockwise.

NOTE: If an output level of less than +43 dBmV is
required, add an attenuator of the appropriate value at
the modulator output.

Example: For an output level of +35 dBmV, add a 12 dB
attenuator pad to the modulator output and set the
output level to +47 dBmV.

F5 - 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 normally 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.

F6 - AUDIO LEVEL Control

The setting of this screwdriver adjustment determines the
peak aural carrier deviation. Clockwise rotation
increases the carrier deviation. After installing the unit,
and with an audio source connected, adjust the AUDIO
LEVEL control for 25 kHz deviation. If an audio
modulation meter is not available, use a TV set and
adjust for equal volume as compared to a known off-air
broadcast. Monitor for a few minutes to assure that
maximum volume of the audio source program does not
cause an over-modulation condition.

F7 - VIDEO LEVEL Control

The setting of this screwdriver adjustment determines the
video modulation level. Clockwise rotation increases the
modulation depth. After installing the unit, and with a
nominal 1 Volt P-P video source connected, adjust the
VIDEO LEVEL control for the correct percentage of
modulation (87.5%). If test equipment is not available for
such measurements, then adjust for proper picture
contrast when viewed on a TV set (compare with known
off-air broadcast picture quality).