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General Instrument STARLINE MB-750D-H Installation Manual

Dual-output amplifier
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Dual-Output Amplifier
Model MB-750D-H
Model MB-750D-H/40
Installation Manual
20 dB
FORWARD CABLE
FWD/
EQUALIZER
RET
IN
JXP
FWD
X0-36
IN
MDR
RESPONSE
20A
CORRECTION
AUTOMATIC CONTROL
BOARD
3
XO-36
SEE-* EQUAL.
*
RETURN
SEE-
ASSEMBLED IN MEXICO
EQUALIZER
Jerrold Communications
General Instrument Corporation
General Instrument
Hatboro, Pa. 19040
POWER SUPPLY
REGULATED DC VOLTAGE
DC (-)
POWER
DC (+)
DC VOLTAGE
ADJUST
ASSEMBLED IN MEXICO
*
EQ-
General Instrument
FORWARD
EQUALIZER
General Instrument Corporation
JXP
GI Communications Division
Hatboro, Pa. 19040
JXP
FWD
DUAL HYBRID
OUT
FWD
POWER DOUBLING
INTR
JXP
MINI-BRIDGER
MB-750D-H
FWD
C80
OUT
C81
C82
20 dB
20 dB
H
PORT
MAN
PORT 3 & 4
L
2
OFF
ACB
SPLIT
JXP
JXP
RET
RET
OUT
IN
AC LINE
VOLTAGE
AC
GROUND
AC
VOLTS (RMS)
FUSE
CAUTION
VOLTAGES IN EXCESS OF 150 VOLTS
MAY BE PRESENT UNDER COVER
X0-36
2
4
X0-36

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  • Page 1 Dual-Output Amplifier Model MB-750D-H Model MB-750D-H/40 Installation Manual General Instrument 20 dB FORWARD CABLE FORWARD FWD/ X0-36 EQUALIZER General Instrument Corporation EQUALIZER GI Communications Division Hatboro, Pa. 19040 DUAL HYBRID POWER DOUBLING INTR MINI-BRIDGER X0-36 MB-750D-H 20 dB 20 dB PORT PORT 3 &...
  • Page 2 General Instrument. General Instrument reserves the right to revise this publication and to make changes in content from time to time without obligation on the part of General Instrument to provide notification of such revision or change.

  • Page 3: Table Of Contents

    Contents Introduction ........................1 Using This Manual ........................1 Related Documentation ......................1 If You Need Help........................2 Calling for Repairs ........................2 Overview ..........................3 Product Description ........................3 Optional Components and Accessories..................4 Assemblies and Modules......................5 Housing Model MB-HSG/60 ....................5 Model MPPS Power Pack ....................5 Forward Amplifier .......................7 Models MBD-SPLT and MBD-DC ..................8 Return Signal Path ......................8...
  • Page 4 Contents Field Installation ......................21 Mechanical Installation ......................21 Housing Connections....................... 21 Mounting the Housing ...................... 21 Power-up ..........................22 Balancing the Amplifier......................22 Manual Thermal Gain Control ....................23 Automatic Level Control ......................23 Closing the Housing ....................... 24 Specifications ........................25 Amplifier ..........................

  • Page 5: Introduction

    Section 1 Introduction ® The General Instrument STARLINE Mini-Bridgers, models MB-750D-H and MB-750D-H/40 are versatile amplifiers used in modern television distribution systems for amplification of standard National Television Sytem Committee (NTSC) television carriers as well as high-definition digital channels. The MB-750D-H and MB-750D-H/40 amplify conventional signals carried in the bandpass between 50 MHz and 550 MHz as well as high-definition digital television signals carried in the bandpass between 550 MHz and 750 MHz.

  • Page 6: If You Need Help

    1-215-674-4800. After business hours, please use 1-215-581-9637. Calling for Repairs If repair is necessary, call the General Instrument Repair Facility at 1-800-642-0442 for a Return for Service Authorization (RSA) number before sending the unit. The RSA number must be prominently displayed on all equipment cartons.

  • Page 7: Overview

    Section 2 Overview Product Description The model MB-750D-H and MB-750D-H/40 Mini-Bridgers are dual output, high gain, three-stage hybrid amplifiers designed to drive both a limited cascade as well as a local distribution system. These amplifiers provide 110-channel capability utilizing a forward bandpass of 50 to 750 MHz and a return path of either 5 to 30 MHz for model MB-750D-H and 5 to 40 MHz for model MB-750D-H/40.

  • Page 8: Optional Components And Accessories

    Overview Figure 1 MB-750D-H and MB-750D-H/40 Mini-Bridger block diagram Optional Components and Accessories The following table provides a list of optional equipment that can be selected to work in conjunction with the mini-bridgers to better satisfy individual system requirements. The table also provides a brief description and basic function of each item to assist the user in the selection process.

  • Page 9: Assemblies And Modules

    Overview Figure 2 Mini-Bridger amplifier module, showing location of accessories Assemblies and Modules This section describes each of the major components and subassemblies associated with the MB-750D-H and MB-750D-H/40 Mini-Bridgers. Housing Model MB-HSG/60 The purpose of the housing is to protect the electronics from the elements and serve as a radiator to dissipate the internally generated heat.
  • Page 10 Overview The pre-regulator is a fixed frequency switching regulator that will present a near perfect power factor to the input line. It includes overvoltage as well as overcurrent protection. The precision output regulator is also protected against overcurrent and short circuits, thus providing a precise output voltage.

  • Page 11: Forward Amplifier

    Overview Figure 4 shows the MPPS power pack installed in the model MB-HSG/60 upper half housing. Figure 4 MPPS Power pack Forward Amplifier The forward amplifier’s electronics consist of two parallel three-stage paths. The first two stages are common to both paths. The preamplifier stage has been selected for its low noise figure, while the output stage provides the desired power at low distortion.

  • Page 12: Models Mbd-Splt And Mbd-Dc

    Overview Figure 5 illustrates the amplifier module with the cover partially cut away to show the location of major components. Figure 5 Forward amplifier module Models MBD-SPLT and MBD-DC One amplifier path in the MB-750D-H* is dedicated to port two as shown in Figure 1. The other path can be used to feed either port three or four by appropriate installation of the furnished MBD-JMP jumper.

  • Page 13: Forward Output Level Control

    Figure 2 shows the location of the optional power control components. Automatic Control Board The Automatic Control Board, General Instrument Model MB-ACB/*, is an optional plug-in board that monitors the amplitude of a designated pilot frequency and automatically adjusts the gain and slope in order to maintain a constant output.

  • Page 14: Preinstallation Procedures

    Section 3 Preinstallation Procedures Prior to installation, the MB-750D-H* amplifier must be equipped with several required accessory items. The required items are to be determined from the data in the system layout documentation. Addition of the required components and bench testing prior to installation is highly recommended.
  • Page 15 Preinstallation Procedures this equalizer installed, the amplifier will reproduce the output tilt of the last upstream amplifier. Example 2: The MB-750D-H* amplifier is to be used in a link following a fiber node. The fiber receiver’s output is flat and connects to the input of the amplifier through 18 dB of cable plus passive loss. Which is the proper equalizer to achieve the 10 dB output tilt from the amplifier? In this instance, the equalizer value can be calculated by using the following method: −...

  • Page 16: Output Passives

    Preinstallation Procedures Figure 6 Tilt versus cable Output Passives The MBD-JMP jumper furnished with the amplifier allows the user to select either port three or port four as the output port. However, if it is desired to provide signal output to both ports, three and four, then the proper output splitter must be installed.

  • Page 17: Power Control Options

    Heatsink compound, General Instrument part number 663-008-000 or its equivalent, can be used between the hybrid flange and the housing to facilitate thermal conductivity. Use of the heatsink compound is not mandatory and is therefore not furnished with the kit.

  • Page 18: Bench Powering The Mb-750S-H/40/E Amplifier

    Preinstallation Procedures Bench Powering the MB-750S-H/40/E Amplifier The recommended method of powering the amplifier on the bench is to apply ac from a 60 Vac supply through a model SSP-PI power combiner to the input port. Alternate methods, such as the use of a 24 Vdc power supply exist and can be used, but the method described here is preferred.

  • Page 19: Figure 9 Restoring Impedance Match, Port 4

    Preinstallation Procedures To improve the match at port 4, merely bend capacitor C38 toward the adjacent connector. The wire which connects to the output connector should also be dressed as close to the circuit board as possible. The components involved in this procedure are illustrated to the left in Figure 9. A more detailed side view of section A-A is illustrated to the right in Figure 9.

  • Page 20: Sweep Response And Gain Testing

    Preinstallation Procedures Sweep Response and Gain Testing Typical connection of test equipment for preinstallation testing is shown in Figure 10. Figure 10 Typical test equipment and connections Simulate the field location of the unit under test by applying the sweep signal through the equivalent cable loss on the bench.

  • Page 21: Manual Thermal Gain Control

    Preinstallation Procedures Manual Thermal Gain Control Manual thermal gain compensation is standard in the amplifier and is designed to compensate for cable attenuation changes with temperature. Control is selectable and depends on the position of the thermal control selector. This jumper is located on the circuit board and can be positioned to .

  • Page 22: Operational Gain

    Preinstallation Procedures Figure 11 MDR-750/10 Board Figure 12 Effect of flatness controls Operational Gain After the required flatness has been obtained, the operational gain of the unit can be measured. Refer to Appendix A, Specifications, for proper operational gain values. The amplifier’s gain is the measured gain plus the sum of all losses, including the power combiner and cable.
  • Page 23 Preinstallation Procedures Automatic Level Control To test the operation of the MB-ACB/* Option, proceed with the following steps: If necessary, refer to the steps for manual thermal control operation previously outlined on page 16. Switch to the ACB control mode by repositioning the thermal control jumper within the module.

  • Page 24: Field Installation

    Section 4 Field Installation Mechanical Installation The conventional method of installation is to suspend the unit by clamping it to the strand installed for the support of the coax cable. Two factory equipped strand clamps are provided for this purpose and can be positioned on either side of the housing to permit convenient curb side entry.

  • Page 25: Power-Up

    Both the input and the output test points are 75 Ohm source impedance, and 20 dB below actual levels. A test probe, General Instrument model GFAL, facilitates connection to the test points and is recommended. All test probes that contain signal matching and attenuating electronics, such as General Instrument model SPD-30, cannot be used for this test as the value measured will be in error.

  • Page 26: Automatic Level Control

    Field Installation resulting measurement will be flat. Figure 6 in Section 3, Preinstallation Procedures, provides a comparison of cable loss versus slope for three different operating frequencies. Open the housing and check the ac and dc voltages to assure that both are within the required limits.

  • Page 27: Closing The Housing

    Field Installation To adjust the automatic gain control: Connect the signal level meter to the output test point and tune the meter to the high end active channel; for example, tune to 745.25 MHz for a 750 MHz system. Turn the control on the MB-ACB/* board to maximum (fully CW).

  • Page 28: Specifications

    Appendix A Specifications The specifications listed below apply to the MB-750D-H* amplifier as used without the return amplifier or automatic control board options. Amplifier Parameter Specification Passband 50 to 750 MHz MB-750D-H 52 to 750 MHz MB-750D-H/40 Minimum full gain at 750 MHz 39 dB Operational gain at 750 MHz 35 dB...

  • Page 29: Automatic Control Board, Mb-Acb

    Specifications Automatic Control Board, MB-ACB/∗ Parameter MB-ACB/403.25 MB-ACB/499.25 403.25 MHz 499.25 MHz Pilot frequency Amplifier output range Minimum + 39 dBmV + 39 dBmV Maximum + 50 dBmV + 50 dBmV ± 0.75 dB ± 0.75 dB Control stiffness for level changes of – 3 to + 4 dB DC supply 24 Vdc, 75 mA 24 Vdc, 75 mA...
  • Page 30 Specifications MB-750S-H/40/E Mini-Bridger Installation Manual...
  • Page 31 General Instrument Corporation GI Communications Division Printed in U.S.A. 436-915-200, 4/95...

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Starline mb-750d-h/40

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