MDS 4790B Original operating instructions

Installation & Operation Guide
MDS 05-2765A01, Rev. B
OCTOBER 2005
400 MHz/900 MHz
Multiple Address System
Master Station Radio
MDS 4790B/9790B

QUICK START GUIDE
1. Install and connect the antenna system to the radio (Page 11).
•Review “Antenna Installation Warning” following the Table of Contents in this manual.
• Use a high-quality gain antenna, mounted in the clear.
• Use high-quality low-loss feedline. Keep the feedline as short as possible, avoiding sharp bends.
2. Switch on the backup battery (Page 17).
• Switch is located behind removable front panel.
• If the battery is discharged, the radio must be operated on AC power for 8 hours before the backup
battery will be available for use.
3. Connect the host computer to the DATA connector on the rear panel (Page 24).
• Connect only the required pins. Do not use a straight-through cable with all pins connected.
• RS/EIA-232 cable length should not exceed 15 meters/50 feet for reliable operation.
4. Verify proper input voltage level and connect power to the radio. Set the power supply
switch(es) to ON.
•Voltage is normally marked on the rear of the power supply. See “Specifications” for voltage ranges.
•The radio can be operated in either a positive or negative ground configuration. The center pin of the
connector is not connected in the radio.
5. Observe front panel indicators for proper operation.
Invisible place holder
ACTIVE (green)—This transceiver board (A or B) is the selected unit.
STBY (yellow)—This transceiver board (A or B) is the standby unit (redundant version only).
ALARM (red)—General fault not covered by the other alarm categories (RX ALR, TX ALR, I/O ALR).
RX ALR (red)—Difficulty receiving. May be due to an antenna problem, receiver fault, or other
condition causing a low received signal level.
TX ALR (red)—Fault with the transmit circuitry.
I/O ALR (red)—The data rate or format is incompatible with the radio settings.
A
B
ACTIVE STBY ALARM RX ALR TX ALR I/O ALR
ACTIVE STBY ALARM RX ALR TX ALR I/O ALR

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide i
TABLE OF CONTENTS
1.0 INTRODUCTION.....................................................................................1
2.0 PRODUCT DESCRIPTION.....................................................................1
2.1 PC-Based Diagnostics .....................................................................2
2.2 Redundant versus Non-redundant Operation ..................................2
2.3 Applications ......................................................................................3
Basic MAS Master Station Operation ...............................................3
2.4 Repeater and Polling Remote Operation .........................................4
Simplex and Switched Carrier Operation.......................................... 6
2.5 Radio Features .................................................................................6
2.6 Model Number Codes ......................................................................7
2.7 Accessories ......................................................................................7
3.0 INSTALLATION PLANNING ....................................................................8
3.1 General Requirements .....................................................................8
Site Selection....................................................................................9
Terrain and Signal Strength ..............................................................9
On-the-Air Test ................................................................................ 10
A Word About Interference.............................................................. 10
3.2 Antenna and Feedline Selection ....................................................11
Antenna System..............................................................................11
Feedline Selection ..........................................................................11
4.0 INSTALLATION PROCEDURES ...........................................................13
4.1 Unpacking and Inspection ..............................................................13
4.2 Mounting the Radio ........................................................................13
Rack Mounting ................................................................................14
Ta b letop Mounting...........................................................................14
Remote Front Panel Mounting—Optional Configuration................. 14
4.3 Primary Power ................................................................................ 15
AC-Powered Units...........................................................................16
DC-Powered Units ..........................................................................16
4.4 Backup Battery ...............................................................................17
Location of Battery Switch ..............................................................17
Low Voltage Disconnect Feature..................................................... 18
Battery Reset Switch (SW1) ...........................................................18
Antenna Installation ........................................................................ 19
Feedline Installation ........................................................................19
4.5 Interface Wiring Connections .........................................................20
Coaxial Connectors (Type-N)—TX, Antenna, RX ...........................20
Ground Connection.........................................................................22

ii MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
Diagnostics Connector—J1 ............................................................ 22
4-Wire Audio Connector—J2 ..........................................................23
Data Connector—J3 ....................................................................... 23
Orderwire—J9.................................................................................25
Alarm Contacts—J10 ......................................................................25
4.6 Post Installation Checks .................................................................26
5.0 START-UP AND OPERATION...............................................................26
5.1 Initial Startup .................................................................................. 26
Normal Indications ..........................................................................27
Coordinating Activities by Orderwire...............................................27
Maximizing RSSI.............................................................................28
5.2 Front Panel Indicators ....................................................................28
LED Indicators ................................................................................ 28
Front Panel Display.........................................................................29
6.0 LOCAL DIAGNOSTICS & CONTROL...................................................30
6.1 PC Connection for Diagnostic Work ...............................................31
6.2 PC Command Summary Tables .....................................................33
Commands and Command Parameters..........................................33
6.3 Command Equivalents for Older Transceivers ............................... 36
6.4 Detailed Command Descriptions ...................................................36
AK [16-Digit Alphanumeric String] ..................................................37
ALARM............................................................................................38
AMASK [0000 0000–FFFF FFFF]...................................................39
ASENSE [HI/LO].............................................................................40
BATT [ON/OFF]...............................................................................40
BAUD [9600 abc] ............................................................................41
BAUD [9600S].................................................................................41
CKEY [ON/OFF]..............................................................................41
CTS [0-255].....................................................................................42
DATE [mmm dd yyyy]...................................................................... 42
DECF [0–100] ................................................................................. 42
DECP [0–100].................................................................................43
DF ...................................................................................................43
DIAGLEV [OFF, 1, 2, 3]................................................................... 43
DKEY ..............................................................................................43
DP...................................................................................................43
EMP [ON/OFF]................................................................................43
HREV..............................................................................................44
IF.....................................................................................................44
INCF [1–99].....................................................................................44
INCP [1–99] .................................................................................... 44
INIT .................................................................................................44
IP.....................................................................................................45
KEY.................................................................................................45
LBC [nnnn]......................................................................................45
LOG [CLR] ...................................................................................... 46
MODEL ...........................................................................................46

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide iii
MODEM [NONE/BELL/4800B/9600B] ............................................ 46
NMASK [0000 0000–FFFF FFFF]...................................................47
OPT.................................................................................................48
OWM [xxxxx] ...................................................................................48
OWN [xxxxx] ...................................................................................48
PTT [0-255].....................................................................................48
PWR [20–37]...................................................................................49
RADIO [AUTO/A/B] .........................................................................49
REPEATER [ON/OFF] ....................................................................49
RMIS ............................................................................................... 50
RMOV .............................................................................................50
RMRD .............................................................................................50
RMST..............................................................................................50
RSSI, RSSI! .................................................................................... 50
RX [xxx]...........................................................................................51
RXLEVEL [–20 to +3]......................................................................51
RXMUTE [ON/OFF/Time in msec]..................................................51
RXPAD [ON/OFF] ...........................................................................52
RXTOT [NONE, 1-1440] .................................................................52
SCD [0-255] .................................................................................... 52
SER.................................................................................................52
SHOW [DC/PWR/CURRENT/RADIO] ............................................52
SREV ..............................................................................................53
SQU [1–10] .....................................................................................53
STANDBY [ON/OFF].......................................................................53
STAT................................................................................................54
SWC [ON/OFF] ............................................................................... 55
TEMP .............................................................................................. 55
TIME [hh:mm:ss].............................................................................55
TOT [ON/OFF, 1-255] ....................................................................56
TX [xxxx] ......................................................................................... 56
TXGAIN [ON/OFF] .......................................................................... 56
TXLEVEL [–20 to +3, AUTO] ..........................................................56
6.5 Configuration and Programming using the Front Panel .................57
Programming and Control Buttons..................................................58
Navigating Through the Front Panel Screens .................................60
Switching the Front Panel Display to Configuration Mode ..............60
Use of Control Buttons in Configuration Mode................................61
Making changes to radio functions .................................................61
6.6 Screen Descriptions .......................................................................61
Group 1—Startup Screen and Menu Directory............................... 62
Group 2—Configuration Screens....................................................62
Group 3—Diagnostic Screens ........................................................62
Group 4—Event Log .......................................................................62
7.0 PROBLEM SOLVING ............................................................................77
7.1 Front Panel LEDs ...........................................................................77
7.2 Chassis-Mounted LEDs .................................................................78
7.3 Problem Solving Using a Connected PC .......................................80

iv MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
7.4 Problem Solving Using the Front Panel Display .............................80
Event Log........................................................................................80
7.5 System Bench Testing Set-Up ........................................................ 81
8.0 REPLACING ASSEMBLIES..................................................................82
8.1 Transceiver Board and Power Supply Assemblies ......................... 82
8.2 Installation & Removal of Backup Battery (P/N 28-1575Axx) ........83
8.3 Front Panel .....................................................................................84
8.4 Operating Frequency Change Considerations ...............................85
MDS 4790—400 MHz Notch-Type Duplexers.................................85
MDS 9790—Bandpass-Type Duplexers..........................................86
MDS 4790/9790 Simplex Radios—With Antenna Switch Modules.87
MDS 4790/970—Front End Helical Coil Alignment.........................87
8.5 Testing and Removing an Internal Duplexer ...................................87
Testing.............................................................................................87
Removing the Internal Duplexer......................................................88
8.6 Testing and Removing the Antenna Switch Module ....................... 89
Testing.............................................................................................89
Removing the Antenna Switch........................................................90
8.7 Cooling Fan Maintenance .............................................................91
9.0 RADIO SOFTWARE UPGRADES ........................................................92
9.1 Obtaining New Code ......................................................................92
9.2 Preparing for Download .................................................................92
9.3 Downloading New Code—Procedure ............................................93
10.0 DIAGNOSTICS & CONTROLOF REMOTE TRANSCEIVERS............93
10.1 Diagnostics Levels .......................................................................94
Level 1—Loopback .........................................................................94
Level 2—Advanced Diagnostics .....................................................94
Level 3—Remote Maintenance.......................................................94
11.0 TECHNICAL REFERENCE.................................................................95
11.1 Technical Specifications ......................................................... 95
11.2 RF Propagation Planning .............................................................97
Fresnel Zone Clearance..................................................................97
Earth Curvature ..............................................................................98
Fade Margins .................................................................................. 99
Calculating Path Loss .....................................................................99
11.3 Formulas for System Planning ..................................................... 99
Free Space Path Loss.....................................................................99
Fresnel Zone Boundary ................................................................ 100
Theoretical Signal Strength...........................................................100
Probability of System Fading ........................................................100
11.4 dBm-Volts-watts Conversion Chart ............................................101
DATA SYNCHRONIZER MODULE ...........................................................102

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide v
Copyright Notice
This Installation and Operation Guide and all software described herein
are protected by copyright: 2005 Microwave Data Systems Inc. All
rights reserved.
Microwave Data Systems Inc. reserves its right to correct any errors and
omissions in this publication.
Antenna Installation Warning
1. All antenna installation and servicing is to be performed by
qualified technical personnel only. When servicing the antenna, or
working at distances closer than those listed below, ensure the
transmitter has been disabled.
2. Typically, the antenna connected to the transmitter is fixed-mounted
on the side or top of a building, or on a tower. Depending upon the
application and the gain of the antenna, the total composite power
could exceed 200 watts EIRP. The antenna location should be such
that only qualified technical personnel can access it, and that under
normal operating conditions no other person can touch the antenna
or approach within 3.05 meters (10 feet) of the antenna.
ISO 9001 Registration
Microwave Data Systems adheres to this internationally-accepted
quality system standard.
Quality Policy Statement
We, the employees of Microwave Data Systems Inc., are committed to
understanding and exceeding our customer’s needs and expectations.
• We appreciate our customer’s patronage. They are our business.
• We promise to serve them and anticipate their needs.
RF Exposure
Separation distances
required for FCC RF
Exposure compliance
Antenna Gain vs. Recommended Safety Distance
(MDS 4790B)
Station Antenna Gain
0–5 dBi 5–10 dBi 10–16.5 dBi
Minimum RF Safety
Distance
0.79 meter 1.41 meters 3.05 meters
Antenna Gain vs. Recommended Safety Distance
(MDS 9790B)
Station Antenna Gain
0–5 dBi 5–10 dBi 10–18.65 dBi
Minimum RF Safety
Distance
0.53 meter 0.94 meter 2.58 meters

vi MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
• We are committed to providing solutions that are cost effective,
innovative and reliable, with consistently high levels of quality.
• We are committed to the continuous improvement of all of our
systems and processes, to improve product quality and increase
customer satisfaction.
Revision Notice
While every reasonable effort has been made to ensure the accuracy of
this manual, product improvements may result in minor differences
between the manual and the product shipped to you. If you have addi-
tional questions or need an exact specification for a product, please con-
tact our Customer Service Team using the information at the back of this
guide. In addition, manual updates can often be found on our Web site
at www.microwavedata.com .
FCC Part 15 Notice
The transceiver complies with Part 15 of the FCC Rules. Operation is
subject to the following two conditions: (1) this device may not cause
harmful interference, and (2) this device must accept any interference
received, including interference that may cause undesired operation.
This device is specifically designed to be used under Section 15.247 of
the FCC Rules and Regulations. Any unauthorized modification or
changes to this device without the express approval of Microwave Data
Systems may void the user’s authority to operate this device. Further-
more, this device is intended to be used only when installed in accor-
dance with the instructions outlined in this manual. Failure to comply
with these instructions may also void the user’s authority to operate this
device.
Warning—400 MHz Distress Beacons
In the U.S.A., the 406 to 406.1 MHz band is reserved for use by distress
beacons. Since the MDS 4790 Series radio is capable of transmitting in
this band, take precautions to prevent the radio from transmitting
between 406 to 406.1 MHz.
ESD Notice
To prevent malfunction or damage to this radio, which may be caused
by Electrostatic Discharge (ESD), the radio should be properly
grounded by connection to the ground stud on the rear panel. In addition,
the installer or operator should follow proper ESD precautions, such as
touching a grounded bare metal object to dissipate body charge, prior to
adjusting front panel controls or connecting or disconnecting cables on
the front or rear panels.

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide vii
Environmental Information
The equipment that you purchased has required the extraction and use
of natural resources for its production. Improper disposal may contami-
nate the environment and present a health risk due to hazardous sub-
stances contained within. To avoid dissemination of these substances
into our environment, and to diminish the demand on natural resources,
we encourage you to use the appropriate recycling systems for disposal.
These systems will reuse or recycle most of the materials found in this
equipment in a sound way. Please contact MDS or your supplier for
more information on the proper disposal of this equipment.

viii MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide 1
1.0 INTRODUCTION
This guide presents installation and operating instructions for
MDS 4790B and MDS 9790B Series master stations. These models are
backward-compatible units designed to work with earlier radio products
manufactured by MDS such as MDS 2300/4300 or MDS 4710B/9710B
Series transceivers. These “B” model master stations can also be used in
systems that include MDS 2100/4100 Series master stations.
The MDS 4790B and 9790B are intended to be used as a replacement
master station or an expansion unit in an existing system which uses the
MDS 2100 or 4100 master station. The MDS x790B master is intended
to be compatible with the 9600, 4800, and Bell 1200 baud data modems
used in the MDS 2100 and 4100 Series while providing limited support
for the DTMF diagnostics when used with InSite™ or the MDS2000
diagnostics program.
This manual begins with an overall description of radio features and is
followed by the steps required to install the unit and place it into normal
operation. Additionally, the guide contains troubleshooting tips for
resolving system difficulties that may be encountered. After installation,
this guide should be kept near the master station for future reference.
2.0 PRODUCT DESCRIPTION
The master station (Figure 1) is a full-duplex data telemetry radio suit-
able for use in a Multiple Address System (MAS) and Supervisory Con-
trol and Data Acquisition (SCADA) applications. The radio uses
microprocessor control and Digital Signal Processing (DSP) technology
to provide highly reliable communications even under adverse condi-
tions.
The MDS 4790B operates in the 400 MHz frequency band (310 to
512 MHz). The MDS 9790 operates between 800 and 960 MHz. Radios
are available in either a redundant configuration or a non-redundant con-
figuration. Refer to Section 2.2 on page 2 for further description.

2 MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
Invisible place holder
Figure 1. MDS 4790/9790 Series Master Station
All assemblies, including the duplexer and power supply, are contained
in the radio’s compact (2RU high) enclosure. (Certain combinations of
receive and transmit frequencies and splits will use an external duplexer
in a separate rack unit.) The radio’s compact size allows it to fit into
most existing systems, in either tabletop or rack mounting arrange-
ments. Connectors are provided on the rear panel for easy connection of
power, antenna, data, alarm and diagnostic functions.
2.1 PC-Based Diagnostics
MDS x790B radios use DTMF diagnostic signaling, and are therefore
not compatible with newer MDS Network-Wide Diagnostics (InSite 6)
which uses packetized digital data to convey diagnostic information.
The MDS x790B is, however, compatible with InSite 5 diagnostic soft-
ware. This software is included on the InSite 6 CD, and includes on-line
instructions for its use. While it does not contain all of the features
offered by InSite 6, the software allows for local or remote connection
to the radio system, and can be used to monitor and adjust several radio
parameters. The front panel monitor function of InSite 5 will not be
available , but key parameters from the master are present along with
polled diagnostic data from the remote radios. Contact MDS for
ordering information. See DIAGNOSTICS & CONTROLOF REMOTE
TRANSCEIVERS on page 93 for details.
2.2 Redundant versus Non-redundant Operation
A redundant configuration means that the master station has two com-
plete transceiver boards and power supplies installed in the enclosure. In
the event of a failure in the primary equipment, the controlling logic
causes a switch-over to the standby unit. The standby transceiver board
ENTER
ESCAPE
ACTIVE
ACTIVE
STBY ALARM RX ALR TX ALR
STBY ALARM RX ALR TX ALR LINE
LINE

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide 3
is constantly monitored for operational readiness, but its power ampli-
fier does not operate when it is in standby mode. In a non-redundant
configuration, there is only one transceiver board installed in the enclo-
sure, and back-up transceiver board operation is not possible.
Transceiver boards may be moved from one master station to another,
or an additional transceiver board may be added to a non-redundant
master station. Installing or replacing a transceiver board will cause the
boards to communicate briefly with each other to establish which board
will operate as the active board and which operates as the standby. For
more information on installation, see Transceiver Board and Power
Supply Assemblies on page 82.
(Note: The
STANDBY ON command must be invoked for a faulty module
to be detected and reported by the radio—See Section 6.0 on page 30 for
details.)
2.3 Applications
The MDS 4790/9790 Series is designed for point-to-multipoint data
transmission in oil and gas pipeline communications, transactional sys-
tems and telecommunications systems. An MAS network provides com-
munications between a central host computer and remote terminal units
(RTUs) or other data collection devices. The operation of the radio
system is transparent to the computer equipment.
The following paragraphs describe some basic setups of the
MDS x790B master station. In some cases, specific settings or com-
mands are necessary for proper operation of the equipment, and these
are discussed in the text that follows. Review this information prior to
installing the equipment, and refer to Section 6.0 on page 30 for detailed
information on issuing commands.
Basic MAS Master Station Operation
Figure 2 shows a typical point-to-multipoint system using an
MDS 4790/9790 Series master station. This is a basic system consisting
of a central master station and several associated remote units.

4 MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
Invisible place holder
Figure 2. Typical MAS Network
The MDS 4790B and 9790B are compatible with the standard 9600,
4800 and 1200 baud modems and 4-wire analog mode used in the
MDS 2100 and 4100 master stations. InSite or MDS 2000 diagnostics
can be used from the master station to read data from MDS x710 or
MDS x310 series remotes, but the remote Deviation and Frequency
Error readouts are not available. Local diagnostic monitoring of the
master station connected to the diagnostics computer is available on the
Network View screen of InSite’s DTMF menu.
DTMF diagnostics polling will interrupt the normal remote transceiver
payload data. Use remote diagnostics if the payload data interruptions
can be tolerated, or pause the system data polling when diagnostics are
in use.
2.4 Repeater and Polling Remote Operation
An MAS system using a repeater station with a polling-remote is shown
in Figure 3. Notice that the polling remote radio is operating in
half-duplex mode and the repeater is operating in full-duplex mode.
The MDS 4790B and 9790B are compatible with the standard 1200,
4800 and 9600 baud modems and with 4-wire analog mode used in an
MDS 2100 and 4100 Repeater and Polling Remote.
Repeater operation works best with the external Data Synchronizer
module attached to the
DATA INTERFACE
port, J3 instead of using the
built-in
REPEATER
mode. (See “REPEATER [ON/OFF]” on page 49..)
This is especially true when using the 4800 baud modem. The Data Syn-
–
IDIAG13.8 VDC
PWR
+
–
HOST SYSTEM
REMOTE RADIO
SWC OFF
RTU
RTU
RTU
RTU
–
IDIAG 13.8VDC
PWR
+
–
–
IDIAG 13.8 VDC
PWR
+
–
–
IDIAG13.8VDC
PWR
+
–
–
IDIAG 13.8 VDC
PWR
+
–
RTU
MDS MASTER
STA TION
CONTINUOUSLY
KEYED
REMOTE RADIO
SWC OFF
REMOTE RADIO
SWC OFF
REMOTE RADIO
SWC OFF
REMOTE RADIO
SWC OFF

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide 5
chronizer module buffers the receive data and re-transmits it with ideal
timing. It is important to leave the built-in
REPEATER
mode set to
OFF
for
the MDS x790B to use the external Data Synchronizer module. (See
“DATA SYNCHRONIZER MODULE” on page 102. for more details.)
The internal
REPEATER ON
mode can be used for 1200 and 9600 baud if
the remotes are MDS 2310 or 4310 Series radios. For MDS 4710 and
9710 remotes, the remote’s PTT delay must be set to 5 ms for reliable
operation. When operating 4-wire analog Repeaters (
MODEM NONE
) the
Data Synchronizer module is not used.
Switched Carrier (
SWC
) should always be
ON
for the Repeater because it
will be receiving from remote radios operating in switched carrier mode.
(See “SWC [ON/OFF]” on page 55..) The Repeater will usually be con-
tinuously keyed in such cases. When the radio is used as a polling
remote listening to a continuously keyed repeater station,
SWC
should be
set to
OFF .
Invisible place holder
Figure 3. Typical Repeater and Polling-Remote Network
The Polling Remote is capable of full-duplex operation but will gener-
ally be used with the RXMUTE command ON and set to 15 ms to prevent
it from hearing its own data back from the Repeater. (See “RXMUTE
[ON/OFF/Time in msec]” on page 51..) The repeater squelch tail noise
will also be removed. When
RXMUTE
is
OFF
the Polling Remote will con-
tinuously hear the repeater. Switched Carrier (
SWC
) should always be
OFF
for the Polling Remote if it is receiving from a continuously-keyed
Repeater.
–
IDIAG 13.8 VDC
PWR
+–
HOST SYSTEM
REMOTE RADIO
RTU
RTU
RTU
RTU
–
IDIAG13.8 VDC
PWR
+
–
–
IDIAG13.8 VDC
PWR
+
–
–
IDIAG 13.8 VDC
PWR
+
–
–
IDIAG 13.8 VDC
PWR
+–
RTU
CONTINUOUSLY
KEYED
REMOTE RADIO
REMOTE RADIO
REMOTE RADIO
REMOTE RADIO
POLLING REMOTE
REPEATER
HALF-DUPLEX
SWITCHED CARRIER
TX HIGH
RX LOW
TX LOW
RX HIGH
TX LOW
RX HIGH
TX LOW
RX HIGH
TX LOW
RX HIGH
TX LOW
RX HIGH
TX LOW
RX HIGH

6 MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
MDS InSite or MDS 2000 diagnostics is not supported in Repeater and
Polling Remote modes. The DTMF diagnostics data will not be passed
through an MDS x790B repeater, and an MDS x790B Polling Remote
cannot receive diagnostic data from a MDS 2100 or 4100 Repeater.
However, if the MDS x790B Repeater has the diagnostic connection
directly to its back panel, it will handle diagnostic polls to the remotes
and the MDS x790B Polling Remote. For best results, stop the polling
traffic prior to using diagnostics. Note that radio firmware (software)
revisions 2.0.0 and higher will mute the modem data during DTMF
diagnostics.
Configuring the radio for repeater operation is accomplished by con-
necting the Data Synchronizer Module (P/N 03-1389A02) to the DB-25
DATA connector, J3 on the rear panel.
Simplex and Switched Carrier Operation
System-wide simplex operation is achieved by switching the master sta-
tion carrier on to transmit, then off to receive. The same frequency is
used for both transmit and receive.
Switched carrier, a half-duplex mode, works in the same way, except
that different frequencies are used for transmit and receive.
2.5 Radio Features
Reliability is a hallmark of the MDS 4790/9790 Series design. The radio
employs a one-piece transceiver board which minimizes RF losses and
eliminates the need for inter-board cabling. This also allows easy
plug-in replacement should servicing become necessary.
In addition, the optional redundant version of the radio includes redun-
dant transceiver boards and power supply modules that automatically
become active in the event of a failure in either of the transceiver boards
or power supplies. This ensures continued operation in the event of most
transceiver board failures.
The following list highlights many of the radio’s key features. For a full
listing of specifications, see Section 11.1 on page 95.
• Operation from 15, 24, 48 or 125 Vdc and 115/230 Volt AC
sources.
•Configuration, control and diagnostics from front panel display
or connected PC
• Remote diagnostics via a connected PC and radio software
• Time stamping of alarms and major events
•Flexible mounting (rack or tabletop); front panel can be (option-
ally) mounted separately from radio chassis

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide 7
2.6 Model Number Codes
The radio model number is printed on the label on the end of the radio’s
enclosure and provided through the software command MODEL
(Page 46), provides key information about how the radio was configured
when it was shipped from the factory. This number is subject to many
variations depending on what options are installed and where (country)
the product is used. Contact MDS is you have questions on the meaning
on the code.
2.7 Accessories
The radio can be used with one or more of the accessories listed in
Table 1. Contact the factory for ordering information.
Table 1. Radio Accessories
Option Description Part No.
Diagnostics and
Control Software
PC-based software for local control,
diagnostics, and software upgrades of the
radio.
03-3533A01
Diagnostic and
Control Interface
Cable
Allows connection of a PC to the radio for
control and diagnostics (DB-9 to DB-9).
97-1971A04
Front Panel Back
Mounting Kit
Allows rear-rack mounting of the
detachable front panel. Used in
installations where all controls and
indicators must be accessible from the rear
of the radio.
03-3228A01
12 Vdc Inverter Allows operation of an AC radio on 12 Vdc.
Inverter converts nominal 12 Vdc to 115
Vac.
97-2665A02
Orderwire Adapter External device that allows temporary
voice communication with other units in the
network. Useful for setup and testing of the
radio system.
02-1297A01
Orderwire Handset Telephone handset that is fully compatible
with the MDS O/W Adapter.
12-1307A01
Cavity Filter Kit
(For MDS 9790x)
Removes or attenuates interfering
900 MHz signals from the receiver input.
May be necessary in areas with high
powered stations nearby, such as paging
transmitters. Available for use with an
internal or external duplexer.
03-3621Axx
RF Combiner Panel,
24 MHz splits
(MDS 9790x only)
Combines the outputs of two master
stations into one antenna. Designed for
cases where both masters use a 24 MHz
split.
03-1882Axx
RF Combiner Panel,
9/24 MHz splits
(MDS 9790x only)
Combines the outputs of two master
stations into one antenna. Designed for
cases where one master uses a 9 MHz
split and the other uses a 24 MHz split.
03-3665Axx

8 MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
3.0 INSTALLATION PLANNING
The installation of the radio is not difficult, but it does require some
planning to ensure reliability and efficiency. This section provides tips
for selecting an appropriate site, choosing antennas and feedlines, and
minimizing the chance of interference. This material should be reviewed
before beginning equipment installation.
3.1 General Requirements
There are three main requirements for installing the radio—adequate
and stable primary power, a good antenna system, and the correct inter-
face between the radio and the data device. Figure 4 shows a typical sta-
tion arrangement.
Invisible place holder
Figure 4. Typical Station Arrangement
Redundant Radio
Upgrade Kit
Adds an additional transceiver board and
power supply to a single-radio chassis.
Operating frequency must be specified
when ordering.
Consult
Factory
Data Synchronizer
Module Kit
Processes incoming data and regenerates
it for retransmission to the next station.
Improves bit-error rate in repeater systems.
02-1565A02
Table 1. Radio Accessories (Continued)
Option Description Part No.
TO INPUT
POWER SOURCE
LOW LOSS
COAXIAL CABLE
OMNIDIRECTIONAL
ANTENNA
HOST COMPUTER
DIAGNOSTICS
COMPUTER
ENTER
ESCAPE
ACTIVE
ACTIVE
STBY ALARM RX ALR TX ALR
STBY ALARM RX ALR TX ALR LINE
LINE

MDS 05-2765A01, Rev. B MDS x790B Series I/O Guide 9
Site Selection
For a successful installation, careful thought must be given to selecting
the site for the master station and the remote radios. Suitable sites should
offer:
•An antenna location that provides an unobstructed path to all the
remote radios in the system
•Asource of adequate and stable primary power
• Suitable entrances for antenna, interface or other required
cabling.
These requirements can be quickly determined in most cases. A possible
exception is the first item—verifying that an unobstructed transmission
path exists. UHF radio signals travel primarily by line-of-sight, and
obstructions between the sending and receiving stations will affect
system performance.
If you are not familiar with the effects of terrain and other obstructions
on radio transmission, the following discussion will provide helpful
background.
Terrain and Signal Strength
A line-of-sight path between stations is highly desirable and provides
the most reliable communications link in all cases. A line-of-sight path
can often be achieved by mounting each station antenna on a tower or
other elevated structure that raises it high enough to clear surrounding
terrain and other obstructions.
The requirement for a clear transmission path depends on the distance
to be covered by the system. If the system is to cover only a limited dis-
tance, say 3.1 miles (5 km), then some obstructions in the transmission
path may be tolerable. For longer range systems, any obstruction could
compromise the performance of the system, or block transmission
entirely.
The signal strength at the receiver must exceed the sensitivity limit by
an amount known as the fade margin to provide reliable operation under
various conditions.
Section 11.2 on page 97 includes a detailed discussion of path planning,
and should be reviewed before beginning an installation. Computer soft-
ware is also available for this purpose that can greatly simplify the steps
involved in planning a path.

10 MDS x790B Series I/O Guide MDS 05-2765A01, Rev. B
On-the-Air Test
If you’ve analyzed the proposed transmission path and feel that it is
acceptable, an on-the-air test of the equipment and path should be con-
ducted. This not only verifies the path study results, but allows you to
see firsthand the factors involved at each installation site.
The test can be performed by installing a radio at each end of the pro-
posed link and checking the RSSI value reported at the radio’s front
panel display. (See Front Panel Indicators on page 28.) If adequate
signal strength cannot be obtained, it may be necessary to mount the sta-
tion antennas higher, use higher gain antennas, or select a different site
for one or both stations.
To prepare the equipment for an on-the-air test, follow the general
installation and operation procedures given in this guide and become
familiar with the operating instructions given in Section 5.0 on page 26.
A Word About Interference
Interference is possible in any radio system. However, since the
MDS 4790/9790 Series is designed for use in a licensed system, inter-
ference is less likely because geographic location and existing operating
frequencies are taken into account when allocating frequencies.
The risk of interference can be further reduced through prudent system
design and configuration. Allow adequate separation between frequen-
cies and radio systems.
Keep the following points in mind when setting up your radio system:
1. Systems installed in lightly populated areas are least likely to
encounter interference; those in urban and suburban environments
are more likely to be affected by other devices operating on nearby
frequencies.
2. Directional antennas should be used at the remote end of the link.
They confine the transmission and reception pattern to a compara-
tively narrow beam, which minimizes interference to and from sta-
tions located outside the pattern.
3. If interference is suspected from another system, it may be helpful
to use antenna polarization that is opposite to the interfering sys-
tem’s antennas. An additional 20 dB (or more) of attenuation to
interference can be achieved by using opposite antenna polarization.