Broadcast Electronics AM-500A 500 WATT User manual

AM–500A 500 WATT
AM–1A 1 KILOWATT
AM BROADCAST
TRANSMITTERS
October, 1999 IM No. 597–1112

IMPORTANT INFORMATION
EQUIPMENT LOST OR DAMAGED IN TRANSIT.
When delivering the equipment to you, the truck driver or carrier’s agent will present a receipt for your signature.
Do not sign it until you have: 1) inspected the containers for visible signs of damage and 2) counted the containers
and compared with the amount shown on the shipping papers. If a shortage or evidence of damage is noted, insist
that notation to that effect be made on the shipping papers before you sign them.
Further, after receiving the equipment, unpack it and inspect thoroughly for concealed damage. If concealed dam-
age is discovered, immediately notify the carrier, confirming the notification in writing, and secure an inspection re-
port. This item should be unpacked and inspected for damage WITHIN 15 DAYS after receipt. Claims for loss or
damage will not be honored without proper notification of inspection by the carrier.
RF PRODUCT TECHNICAL ASSISTANCE – REPAIR SERVICE – REPLACEMENT PARTS.
Technical assistance is available from Broadcast Electronics by letter, prepaid telephone, fax, or E–mail. Equip-
ment requiring repair or overhaul should be sent by common carrier, prepaid, insured, and well protected. If proper
shipping materials are not available, contact the Customer Service Department for a shipping container. Do not the
mail equipment. We can assume no liability for inbound damage, and necessary repairs become the obligation of
the shipper. Prior arrangement is necessary. Contact the Customer Service Department for a Return Authoriza-
tion.
Emergency and warranty replacement parts may be ordered from the following address. Be sure to include the
equipment model number, serial number, part description, and part number. Non–emergency replacement parts
may be ordered directly from the Broadcast Electronics stock room by fax at the number shown below.
FACILITY CONTACTS –
Broadcast Electronics, Inc. – Quincy Facility
4100 N. 24th St. P.O. BOX 3606
Quincy, Illinois 62305
Telephone: [phone]
Fax: [phone]
E–Mail: General – [email protected]
Web Site: www.bdcast.com
RF PRODUCT TECHNICAL ASSISTANCE – REPAIR – EMERGENCY/WARRANTY REPLACEMENT PARTS –
Telephone: [phone]
E–Mail: [email protected]
Fax: [phone]
NON–EMERGENCY REPLACEMENT PARTS –
Fax: [phone]
RETURN, REPAIR, AND EXCHANGES.
Do not return any merchandise without our written approval and Return Authorization. We will provide special ship-
ping instructions and a code number that will assure proper handling and prompt issuance of credit. Please furnish
complete details as to circumstances and reasons when requesting return of merchandise. All returned merchan-
dise must be sent freight prepaid and properly insured by the customer.
WARRANTY ADJUSTMENT.
Broadcast Electronics, Inc. warranty is included in the Terms and Conditions of Sale. In the event of a warranty
claim, replacement or repair parts will be supplied F.O.B. factory. At the discretion of Broadcast Electronics, the
customer may be required to return the defective part or equipment to Broadcast Electronics, Inc. F.O.B. Quincy,
Illinois. Warranty replacements of defective merchandise will be billed to your account. This billing will be cleared
by a credit issued upon return of the defective item.
PROPRIETARY NOTICE.
This document contains proprietary data of Broadcast Electronics, Inc. No disclosure, reproduction, or use of any
part thereof may be made except by prior written permission.
MODIFICATIONS.
Broadcast Electronics, Inc. reserves the right to modify the design and specifications of the equipment in this manu-
al without notice. Any modifications shall not adversely affect performance of the equipment so modified.

WARNING
OPERATING HAZARDS
READ THIS SHEET AND OBSERVE ALL SAFETY PRECAUTIONS
ALL PERSONS WHO WORK WITH OR ARE EXPOSED TO POWER TRANSISTORS MUST TAKE PRECAUTIONS
TO PROTECT THEMSELVES AGAINST POSSIBLE SERIOUS BODILY INJURY. EXERCISE EXTREME CARE
AROUND SUCH PRODUCTS. UNINFORMED OR CARELESS OPERATION OF THESE DEVICES CAN RESULT
IN POOR PERFORMANCE, DAMAGE TO THE DEVICE OR PROPERTY, SERIOUS BODILY INJURY, AND POSSI-
BLY DEATH.
DANGEROUS HAZARDS EXIST IN THE OPERATION OF POWER TRANSISTORS
The operation of power tubes and power transistors involves one or more of the following hazards, any one of which,
in the absence of safe operating practices and precautions, could result in serious harm to personnel.
A. HIGH VOLTAGE – Normal operating voltages can be deadly. Additional information follows.
B. RF RADIATION – Exposure to RF radiation may cause serious bodily injury possibly resulting in
blindness or death. Cardiac pacemakers may be affected. Additional information follows.
C. BERYLLIUM – OXIDE POISONING – Dust or fumes from BeO ceramics used as thermal links with
power transistors are highly toxic and can cause serious injury or death. Additional information follows.
D. HOT SURFACES – Surfaces of air–cooled heat sinks radiators can reach temperatures of 100 degrees
centigrade and cause burns if touched. Additional information follows.
E. RF BURNS – Circuit boards with RF power transistors contain high RF potentials. Do not operate an RF
power module with the cover removed.
HIGH VOLTAGE
The transmitter operates at voltages high enough to kill through electrocution. Personnel should always break the
primary circuits when access to the transmitter is required.
RADIO FREQUENCY RADIATION
Exposure of personnel to RF radiation should be minimized, personnel should not be permitted in the vicinity of open
energized RF generating circuits, or RF transmission systems (waveguides, cables, connectors, etc.), or energized
antennas. It is generally accepted that exposure to “high levels” of radiation can result in severe bodily injury includ-
ing blindness. Cardiac pacemakers may be affected.
The effect of prolonged exposure to “low level” RF radiation continues to be a subject of investigation and controver-
sy. It is generally agreed that prolonged exposure of personnel to RF radiation should be limited to an absolute mini-
mum. It is also generally agreed that exposure should be reduced in working areas where personnel heat load is
above normal. A 10 mW/cm2per one tenth hour average level has been adopted by several U.S. Government agen-
cies including the Occupational Safety and Health Administration (OSHA) as the standard protection guide for em-
ployee work environments. An even stricter standard is recommended by the American National Standards Institute
which recommends a 1.0 mW/cm2per one tenth hour average level exposure between 30 Hz and 300 MHz as the
standard employee protection guide (ANSI C95.1–1982).
RF energy must be contained properly by shielding and transmission lines. All input and output RF connections, such
as cables, flanges and gaskets must be RF leakproof. Never operate a power tube without a properly matched RF
energy absorbing load attached. Never look into or expose any part of the body to an antenna, open RF generating
circuit, or RF transmission system while energized. Monitor the tube and RF system for RF radiation leakage at regu-
lar intervals and after servicing.
DANGER –– BERYLLIUM OXIDE CERAMICS (BeO) – AVOID BREATHING DUST OR FUMES
BeO ceramic material is used as a thermal link to carry heat from a transistor to the heat sink. Do not perform any
operation on any BeO ceramic which might produce dust or fumes, such as grinding, grit blasting, or acid cleaning.
Beryllium oxide dust or fumes are highly toxic and breathing them can result in serious personal injury or death. BeO
ceramics must be disposed of only in a manner prescribed by the device manufacturer.
HOT SURFACES
Heat sinks and reject loads are air–cooled or conduction–cooled. The air–cooled external surface can operate at a
high temperature (up to 100°C). All hot surfaces may remain hot for an extended time after the transmitter is oper-
ated to off. To prevent serious burns, take care to prevent and avoid any bodily contact with these surfaces both dur-
ing and for a reasonable cooling down period after operation.

TRANSMITTER WARRANTY VOID NOTICE
THE PRODUCT WARRANTY WILL BE VOID IF THE
TRANSMITTER IS INSTALLED AT A SITE WITH
INADEQUATE LIGHTNING PROTECTION AND A
DEFECTIVE TRANSMISSION LINE SYSTEM.
The transmitter is covered by a two year limited product warranty from Broadcast Elec
tronics. However, the transmitter must be properly installed at a site with adequate
lightning protection and transmission line systems. TO ENSURE THE TRANSMIT
TER WARRANTY IS VALID, the transmitter must be installed: 1) as described by the
INSTALLATION procedures presented in SECTION II of this manual, 2) at a transmitter
site with a lightning protection system described in TRANSMITTER SITE LIGHTNING
PROTECTION SYSTEM CHECKOUT (refer to SECTION II of this manual), and 3) at a
transmitter site with a transmission line system described in TRANSMISSION LINE
AND ANTENNA CHECKOUT (refer to SECTION II of this manual). FAILURE TO
PROPERLY INSTALL THE TRANSMITTER, PROVIDE AN ADEQUATE LIGHT
NING PROTECTION SYSTEM, OR PROVIDE AN ADEQUATE TRANSMISSION
LINE SYSTEM WILL VOID THE WARRANTY ON THE TRANSMITTER. If any
questions develop concerning the transmitter warranty and installation site systems, con
tact the Broadcast Electronics Customer Service Department.
BROADCAST ELECTRONICS, INC.

NOTICE TO THE EQUIPMENT USER
FCC Rule 73.1590 mandates the licensee of each AM station to make measurements for
spurious and harmonic emissions to show compliance with the transmission system re
quirements of Section 73.44 of the Commission's Rules. It is the broadcast station's respon
sibility to ensure that the audio signal input to the Broadcast Electronics A-Series trans
mitters conforms to the audio standard NRSC-1 (published as ANSI/EIA-549-1988). This
is a mandatory requirement to ensure that the equipment complies to Section 73.44 and
Section 73.128(C) of the Commission's Rules.
BROADCAST ELECTRONICS, INC.

WARNING WARNING
OPERATING HAZARDS
WARNING
WARNING
THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT
GROUNDS WITH HIGH AC AND DC POTENTIALS WITH
RESPECT TO THE CABINET WHICH IS AT EARTH PO
TENTIAL. DO NOT ENERGIZE THE TRANSMITTER
WITH TEST EQUIPMENT CONNECTED TO THE
TRANSMITTER OUTPUT NETWORK, RF POWER MOD
ULE, RF COMBINER, OR POWER SUPPLY COMPO
NENTS.
The Broadcast Electronics AM transmitters contain high voltages and currents. If safety precautions are
not practiced, contact with the high voltages and currents could cause serious injury or death. The trans
mitter is equipped with many built-in safety features, however good judgement, care, and common sense
must be practiced to prevent accidents.
In addition to high voltages and currents, the AM transmitters contain multiple circuit grounds with
high ac and dc potentials with respect to the cabinet which is at earth potential. The potentials could
cause serious injury or death if maintenance personnel simultaneously touch a circuit ground and the
cabinet. As a result, operation of the transmitter with test equipment connected to transmitter output
network, RF power module, RF combiner, or power supply components is extremely dangerous and must
not be attempted. Therefore, never energize the transmitter with test equipment connected to the trans
mitter output network, RF power module, RF combiner, or power supply components. Test equipment
may be connected to the ECU circuit boards from the front of the transmitter using the supplied extender
circuit board with power energized if required.

i
Broadcast Electronics 1996
ALL RIGHTS RESERVED
Printed in the U.S.A.
TABLE OF CONTENTS
PARAGRAPH PAGE NO.
SECTION I GENERAL INFORMATION
1-1 INTRODUCTION 1-1
1-3 EQUIPMENT DESCRIPTION 1-1
1-4 GENERAL 1-1
1-6 EXCITER/CONTROL UNIT 1-1
1-12 OUTPUT NETWORK CHASSIS 1-3
1-16 TRANSMITTER CONFIGURATIONS 1-3
1-18 ACCESSORIES AND SPARE PARTS KITS 1-3
1-20 EQUIPMENT SPECIFICATIONS 1-3
SECTION II INSTALLATION
2-1 INTRODUCTION 2-1
2-3 UNPACKING 2-1
2-6 ENVIRONMENTAL REQUIREMENTS 2-1
2-8 INSTALLATION 2-1
2-10 EQUIPMENT PLACEMENT 2-1
2-12 RACK PREPARATION 2-1
2-14 EQUIPMENT INSTALLATION 2-2
2-15 TRANSMITTER MOUNTING 2-2
2-19 COMPONENT INSTALLATION 2-8
2-22 ECU CIRCUIT BOARDS 2-8
2-23 RF POWER MODULE 2-8
2-24 BATTERY INSTALLATION 2-8
2-25 CIRCUIT BOARD PROGRAMMING 2-8
2-27 EXCITER CIRCUIT BOARD 2-10
2-36 STEREO CIRCUIT BOARD 2-10
2-41 CONTROLLER CIRCUIT BOARD 2-13
2-54 POWER SUPPLY CIRCUIT BOARD 2-15
2-57 REMOTE CONTROL CONNECTIONS 2-15
2-58 GENERAL 2-15
2-83 WIRING 2-18
2-85 AUDIO INPUT CONNECTION 2-18
2-87 EXTERNAL STEREO RF INPUT 2-19
2-88 RF TRANSMISSION LINE CONNECTION 2-19
2-89 EXTERNAL INTERLOCK 2-19
2-90 MODULATION MONITOR 2-20
2-91 AC POWER CONNECTIONS 2-20
2-94 GROUND 2-20
2-95 TRANSMITTER SITE LIGHTNING PROTECTION 2-22
SYSTEM CHECKOUT
2-97 ANTENNA BALL-GAP LIGHTNING 2-22
ARRESTOR
2-101 ANTENNA-TUNING-UNIT SPARK-GAP 2-22
LIGHTNING ARRESTOR
2-102 TRANSMITTER SITE GROUNDING SYSTEM 2-24
2-103 CABLE PROTECTION 2-24
2-110 ANTENNA RF FEED LINE 2-24

ii
PARAGRAPH PAGE NO.
2-111 TRANSMISSION LINE AND ANTENNA 2-25
CHECKOUT
2-113 ANTENNA VSWR 2-25
2-114 COAXIAL SWITCH CONTROLLER. 2-25
2-115 ATU AND PHASOR CHECKOUT 2-25
2-116 INITIAL CHECKOUT 2-25
2-118 PRELIMINARY OPERATION AND ADJUSTMENT 2-26
2-123 POWER LEVEL AND MODULATION MONITOR 2-26
CALIBRATION ADJUSTMENTS
2-135 STEREO ADJUSTMENT 2-28
2-146 SINGLE CHANNEL LEVEL 2-30
SECTION III OPERATION
3-1 INTRODUCTION 3-1
3-3 CONTROLS AND INDICATORS 3-1
3-5 OPERATION 3-12
3-6 TURN-ON 3-12
3-7 OPERATION 3-12
3-14 TURN OFF 3-12
3-16 METERING 3-13
3-17 FORWARD POWER 3-13
3-18 REFLECTED POWER 3-13
3-19 POWER ADJUST 3-13
3-21 MONO/STEREO OPERATION 3-13
3-23 STEREO OPERATION 3-13
3-24 MONO OPERATION 3-13
3-27 PILOT CONTROL 3-14
3-29 EXCITER MONITOR OPERATION 3-14
3-31 MONO/STEREO INDICATIONS 3-14
3-32 INPUT SELECTION 3-14
3-33 POLARITY SELECTION 3-14
3-34 X10 AUTORANGE INDICATIONS 3-14
3-35 FAULT RESET 3-15
3-37 POWER SUPPLY FAULT RESET 3-15
3-39 OVER-CYCLE OFF 3-15
3-41 OVER-MODULATION PWM MUTE 3-15
3-43 TRANSMITTER MONITOR 3-15
3-45 BATTERY TEST 3-15
3-47 CONTROLLER PWM MUTE INDICATOR 3-15
3-49 CONTROLLER REMOTE FAILSAFE 3-16
INDICATOR.
3-51 EXCITER LOCK INDICATOR 3-16
3-53 EXCITER +5V/+15V/-15V INDICATORS 3-16
3-55 STEREO EQUALIZATION INDICATORS 3-16
3-57 RF POWER MODULE INDICATORS 3-16
3-59 HIGH AC LINE CONDITIONS 3-16
SECTION IV THEORY OF OPERATION
4-1 INTRODUCTION 4-1
4-3 OVERALL OPERATION 4-1

iii
PARAGRAPH PAGE NO.
4-5 POWER SUPPLY CIRCUITRY OPERATION 4-1
4-7 POWER SUPPLY CIRCUIT BOARD OPERATION 4-1
4-9 RF CIRCUITRY OPERATION 4-1
4-11 RF POWER MODULE MODULATOR CIRCUIT 4-1
BOARD OPERATION
4-13 RF POWER MODULE AMPLIFIER CIRCUIT 4-1
BOARD OPERATION
4-15 CONTROLLER CIRCUIT BOARD OPERATION 4-1
4-17 EXCITER CIRCUIT BOARD OPERATION 4-1
4-19 STEREO CIRCUIT BOARD OPERATION 4-1
SECTION V MAINTENANCE
5-1 INTRODUCTION 5-1
5-3 SAFETY CONSIDERATIONS 5-1
5-7 FIRST LEVEL MAINTENANCE 5-1
5-9 ROUTINE MAINTENANCE 5-2
5-10 INSPECTION AND CLEANING 5-2
5-11 CONTROLLER BATTERY 5-2
5-12 AIR FILTER 5-2
5-13 FLUSHING FAN 5-2
5-15 SPARK GAP 5-2
5-16 SECOND LEVEL MAINTENANCE 5-2
5-19 OVERALL TRANSMITTER 5-3
5-20 ELECTRICAL ADJUSTMENTS 5-3
5-21 TRANSMITTER FREQUENCY 5-3
RE-PROGRAMMING
5-23 TROUBLESHOOTING 5-3
5-25 TRANSMITTER INDICATORS 5-4
5-26 TRANSMITTER TROUBLESHOOTING 5-6
PROCEDURES
5-27 TRANSMITTER COMPONENT LOCATIONS 5-6
5-28 POWER SUPPLY CIRCUIT BOARD 5-11
5-29 SAFETY CONSIDERATIONS 5-11
5-31 REMOVING/INSTALLING A POWER SUPPLY 5-11
CIRCUIT BOARD
5-35 TROUBLESHOOTING PROCEDURES 5-11
5-37 RF POWER MODULE 5-17
5-38 SAFETY CONSIDERATIONS 5-17
5-40 RF POWER MODULE ASSEMBLY PROCEDURE 5-17
5-42 RF POWER MODULE EXCHANGE PROGRAM 5-18
5-44 TROUBLESHOOTING PROCEDURES 5-18
5-46 DIRECTIONAL COUPLER/LIGHTNING 5-20
DETECTION/LIGHTNING PROTECTION CIRCUIT
BOARDS
5-47 SAFETY CONSIDERATIONS 5-20
5-49 ELECTRICAL ADJUSTMENTS 5-21
5-50 MODULATION CALIBRATION CONTROLS 5-21
5-51 DIRECTIONAL COUPLER NULL CONTROLS 5-21
5-52 TROUBLESHOOTING PROCEDURES 5-21
5-55 ECU 5-22

iv
PARAGRAPH PAGE NO.
5-56 SAFETY CONSIDERATIONS 5-22
5-58 ECU CIRCUIT BOARD INSTALLATION/REMOVAL 5-22
5-61 ELECTRICAL ADJUSTMENTS 5-23
5-63 ECU EXTENDER CIRCUIT BOARD OPERATION 5-23
5-65 CONTROLLER CIRCUIT BOARD ADJUSTMENTS 5-23
5-66 P1 SET - P5 SET CONTROLS 5-23
5-67 FWD AND RFL CALIBRATIONS 5-24
5-68 ECU METER SWITCH CIRCUIT BOARD 5-24
ADJUSTMENTS
5-69 FORWARD POWER METER LOW AND HIGH 5-24
SCALE CALIBRATIONS
5-70 REFLECTED POWER METER LOW AND HIGH 5-24
SCALE CALIBRATIONS
5-71 FWD AND RFL CALIBRATIONS 5-24
5-72 STEREO CIRCUIT BOARD ADJUSTMENTS 5-24
5-73 STEREO ADJUSTMENT 5-24
5-74 EXCITER CIRCUIT BOARD ADJUSTMENTS 5-24
5-75 MODULATION CALIBRATION 5-24
5-76 PHASE MODULATOR CALIBRATION 5-24
5-77 SYMMETRY CONTROL 5-24
5-78 IPM CORRECTION CIRCUIT CONTROLS 5-25
5-79 SINGLE CHAN MONO LEVEL CONTROL 5-25
5-80 AVERAGE MODULATION LIMIT CONTROL 5-25
5-81 NEG LIMIT CONTROL 5-25
5-94 FREQUENCY CALIBRATION CONTROL 5-26
5-104 DISPLAY CIRCUIT BOARD ADJUSTMENTS 5-27
5-105 L/L+R AND R/L-R DISPLAY CALIBRATION 5-27
CONTROL
5-117 TROUBLESHOOTING PROCEDURES 5-27
5-119 COMPONENT REPLACEMENT PROCEDURE 5-32
5-125 INTEGRATED CIRCUITS 5-33
SECTION VI PARTS LIST
6-1 INTRODUCTION 6-1
SECTION VII DRAWINGS
7-1 INTRODUCTION 7-1
SECTION A APPENDIX
Introduction A-1
LIST OF TABLES
TABLE NO. TITLE PAGE NO.
1-1 ELECTRICAL CHARACTERISTICS 1-4
1-2 PHYSICAL AND ENVIRONMENTAL 1-7
CHARACTERISTICS
3-1 AM-1A/AM-500A CONTROLS AND INDICATORS 3-1
3-2 ECU CONTROLS AND INDICATORS 3-3

v
TABLE NO. TITLE PAGE NO.
3-3 POWER MODULE CONTROLS AND INDICATORS 3-10
5-1 AM-1A/AM-500A INDICATORS 5-4
5-2 AM-1A/AM-500A TROUBLESHOOTING 5-7
5-3 POWER SUPPLY MODULE TROUBLESHOOTING 5-16
5-4 RF POWER MODULE TROUBLESHOOTING 5-18
5-5 DIRECTIONAL COUPLER CIRCUIT BOARD 5-21
TROUBLESHOOTING
5-6 LIGHTNING DETECTION CIRCUIT BOARD/SPARK GAP 5-22
TROUBLESHOOTING
5-7 LIGHTNING PROTECTION CIRCUIT BOARD 5-22
TROUBLESHOOTING
5-8 EXCITER CIRCUIT BOARD TROUBLESHOOTING 5-28
5-9 STEREO CIRCUIT BOARD TROUBLESHOOTING 5-30
5-10 CONTROLLER CIRCUIT BOARD TROUBLESHOOTING 5-31
5-11 ECU POWER SUPPLY TROUBLESHOOTING 5-32
6-1 AM-1A REPLACEABLE PARTS LIST INDEX 6-1
LIST OF ILLUSTRATIONS
FIGURE DESCRIPTION PAGE NO.
1-1 AM-1A TRANSMITTER 1-2
2-1 AM-1A/AM-500A TRANSMITTER INSTALLATION 2-3
2-2 AM-1A/AM-500A TRANSMITTER RACK 2-5
INSTALLATION DIAGRAM
2-3 COMPONENT INSTALLATION 2-9
2-4 EXCITER CIRCUIT BOARD PROGRAMMING 2-11
2-5 STEREO CIRCUIT BOARD PROGRAMMING 2-12
2-6 CONTROLLER CIRCUIT BOARD PROGRAMMING 2-14
2-7 REMOTE CONTROL AND AUDIO CONNECTIONS 2-16
2-8 AM-1A/AM-500A RF OUTPUT AND MODULATION 2-19
MONITOR CONNECTORS
2-9 AM-1A/AM-500A PRIMARY AC WIRING 2-21
2-10 ANTENNA LIGHTNING PROTECTION SYSTEM 2-23
2-11 TEST EQUIPMENT CONNECTIONS, POWER LEVEL 2-27
CALIBRATION
2-12 TEST EQUIPMENT CONNECTIONS, SEPARATION 2-29
2-13 EQUALIZATION LISSAJOUS PATTERNS 2-31
3-1 AM-1A/AM-500A CONTROLS AND INDICATORS 3-2
3-2 ECU CONTROLS AND INDICATORS 3-5
3-3 AM-1A POWER MODULE CONTROLS AND 3-11
INDICATORS
4-1 AM-1A/AM-500A TRANSMITTER BLOCK DIAGRAM 4-3
4-2 POWER SUPPLY SIMPLIFIED SCHEMATIC 4-5
4-3 POWER SUPPLY CIRCUIT BOARD SIMPLIFIED 4-7
SCHEMATIC
4-4 RF CIRCUITRY SIMPLIFIED SCHEMATIC 4-9
4-5 MODULATOR CIRCUIT BOARD SIMPLIFIED 4-11
SCHEMATIC
4-6 POWER AMPLIFIER CIRCUIT BOARD SIMPLIFIED 4-13
SCHEMATIC
4-7 CONTROLLER CIRCUIT BOARD SIMPLIFIED 4-15
SCHEMATIC

vi
FIGURE DESCRIPTION PAGE NO.
4-8 EXCITER CIRCUIT BOARD SIMPLIFIED 4-19
SCHEMATIC
4-9 STEREO CIRCUIT BOARD SIMPLIFIED 4-21
SCHEMATIC
5-1 AM-1A/AM-500A COMPONENT LOCATOR 5-12
5-2 ECU/COMBINER COMPONENT LOCATOR 5-15
5-3 EXCITER CIRCUIT BOARD ADJUSTMENT 5-26
CONTROLS

1-1
SECTION I
GENERAL INFORMATION
1-1. INTRODUCTION.
1-2. Information presented by this section provides a general description of the Broadcast
Electronics AM-1A/AM-500A transmitters and lists equipment specifications.
1-3. EQUIPMENT DESCRIPTION.
1-4. GENERAL.
1-5. The AM-1A transmitter is a 1 kW solid-state C-QUAMstereo AM transmitter designed
for continuous operation in the 522 kHz to 1705 kHz broadcast band (refer to Figure 1-1).
The AM-500A transmitter is a 500 Watt solid-state C-QUAMstereo AM transmitter
designed for continuous operation in the 522 kHz to 1705 kHz broadcast band. The trans
mitters consist of modular components assembled in two individual units. The
exciter/control unit chassis (ECU) contains: 1) the exciter circuit board, 2) the controller
circuit board, 3) the stereo circuit board, and 4) the controller switch and display circuit
board. The output network chassis contains a: 1) power amplifier module, 2) power supply
module, 3) bandpass filter assembly, 4) directional coupler circuit board, 5) lightning
protection circuit board, and 6) lightning detection circuit board. Specific transmitter fea
tures include:
1. Built-in C-QUAMAM stereo circuitry.
2. A high efficiency Class E solid-state RF power amplifier module.
3. A high efficiency switching power supply.
4. A CMOS digital controller with extensive VSWR detection and foldback circuitry
which reduces carrier interruptions caused by weather disturbances.
1-6. EXCITER/CONTROL UNIT. The transmitter exciter/control unit (ECU) is a modular as
sembly containing plug-in stereo, exciter, and controller circuit boards. In addition to the
circuit boards, the ECU is equipped with forward and reflected power meters to provide
transmitter output power status indications.
1-7. Stereo Circuit Board. The ECU stereo circuit board is a modular plug-in assembly con
taining C-QUAMAM stereo circuitry. The C-QUAMstereo system is a mode of AM
stereo transmission utilizing amplitude modulated monaural (L+R) information and inde
pendently quadrature modulated stereo (L-R) information. The results produce a stereo
transmission system compatible with mono receivers.
1-8. The stereo circuit board is designed with remote/local controlled mono left, mono right,
mono L+R, and stereo modes of operation. Two equalization circuits are provided to allow
the transmitter to be configured for operation into two different antennas.
C-QUAMis a registered trademark of Motorola Inc.

1-2
FIGURE 1-1. AM-1A TRANSMITTER
597-1112-1
COPYRIGHT 1996 BROADCAST ELECTRONICS, INC
AM-1A TRANSMITTER
1-9. Exciter Circuit Board. The ECU exciter circuit board is a modular plug-in exciter assem
bly. Instrumentation amplifiers provide balanced left and right channel transformerless
audio inputs. The exciter carrier frequency is established by a digital frequency synthe
sizer. The synthesizer is a phase-locked-loop circuit which provides extremely accurate
and reliable carrier frequency operation. A PWM (pulse-width-modulation) circuit is used
to generate an RF drive signal for application to a modulator circuit board in an RF power
module. If a stereo circuit board failure is encountered or when the stereo circuit board is
removed from the ECU chassis, the exciter circuitry is designed to automatically configure
to monophonic operation.
1-10. Controller Circuit Board. All transmitter control operations are directed by the ECU con
troller circuit board. The controller circuit board consists of CMOS logic control and moni
toring circuitry. The circuitry is designed to interface to all popular remote control systems
such as the Broadcast Electronics VMC-16 voice remote control system.
1-11. The transmitter power is controlled by a power control circuit. The circuit allows the
transmitter to be operated at five power levels. A power trim circuit allows the transmitter
output power to be adjusted to a precise level. An antenna interlock circuit is provided to
prevent the transmitter from operating into an incorrect antenna. A reflected power detec
tion circuit operates in association with the power control circuit to foldback the transmit
ter power during high VSWR conditions. In addition to the reflected power detector, a
lightning detector circuit is provided to mute the transmitter when high voltage is present
at the transmitter output during a lightning storm.

1-3
1-12. OUTPUT NETWORK CHASSIS. The output network chassis contains: 1) a bandpass filter,
2) an RF power module, 3) a power supply circuit board, 4) a lightning detection circuit
board, 5) a lightning protection circuit board, and 6) a directional coupler assembly. The
bandpass filter is provided to attenuate all harmonic frequencies to FCC, DOC, and CCIR
levels.
1-13. RF Power Module. Each transmitter is equipped with a single RF power module. The
power module is a modular plug-in assembly containing two RF power amplifier circuit
boards and one modulator circuit board. The AM-1A power module will produce 1100
watts of RF power. The AM-500A power module will produce 550 watts of RF power.
1-14. The RF power module is designed using Class E amplifier technology. A Class E amplifier
exhibits high efficiency and provides superior audio performance. In addition to the supe
rior efficiency and audio performance, the power module is designed to be removed from
the chassis for maintenance.
1-15. Power Supply. A modular switching power supply provides dc operating potentials for the
transmitter. The power supply design uses an SCR controlled bridge to rectify the ac line
voltage into a dc potential. The supply is filtered and routed to the RF power module for
control and regulation. A fault detection circuit monitors power supply activity for failure
conditions. A separate modular switching power supply provides operating potentials for
the ECU circuitry.
1-16. TRANSMITTER CONFIGURATIONS.
1-17. The transmitters can be ordered in the following configurations:
P/N DESCRIPTION
907-1000-001 AM-1A 1 kW AM Transmitter for operation
in the 522 kHz to 1705 kHz broadcast band,
196V - 252V ac 50/60 Hz single phase supply.
907-0500-001 AM-500A 500W AM Transmitter for operation
in the 522 kHz to 1705 kHz broadcast band,
196V - 252V ac 50/60 Hz single phase supply.
1-18. ACCESSORIES AND SPARE PARTS KITS.
1-19. The following text presents accessories and spare parts kits available for use with the
AM-1A/AM-500A transmitters.
P/N DESCRIPTION
977-0027 Recommended semiconductor kit.
977-0028 100% semiconductor kit.
977-0029 Recommended spare parts kit. Includes selected
meters, switches, fuses, filters, etc. Does not
include semiconductors.
977-0037 Basic semiconductor kit for AM-A series, AM-1A,
AM-6A, AM-10A.
1-20. EQUIPMENT SPECIFICATIONS.
1-21. Refer to Table 1-1 for electrical specifications or Table 1-2 for physical specifications of the
AM-1A/AM-500A transmitter.

1-4
TABLE 1-1. ELECTRICAL CHARACTERISTICS
(Sheet 1 of 3)
PARAMETER SPECIFICATION
RF POWER OUTPUT
AM-1A 5 watts to 1100 watts. Five preset power levels
available by local or remote control.
AM-500A 5 watts to 550 watts. Five preset power levels
available by local or remote control.
RF CARRIER FREQUENCY 522 kHz to 1705 kHz (as ordered).
RANGE Accommodates 9 kHz or 10 kHz channel spacing
(9 kHz spacing requires an optional crystal).
RF OUTPUT IMPEDANCE 50 Ohms, unbalanced.
OUTPUT CONNECTOR Type N Connector.
LOAD VSWR 1.30 : 1 at full carrier power. Will operate into a
higher VSWR with automatic power reduction.
Open and short circuit protected. Load VSWRs
higher than 1.30 : 1 are accommodated with an
optional matching network.
HARMONIC AND SPURIOUS Meets or exceeds FCC, DOC, and CCIR require-
SUPPRESSION ments when preceded by external NRSC-1 com-
patible audio low-pass filters.
CARRIER FREQUENCY ±3ppm, 0°to 50°C (+32°to +122°F).
STABILITY
CARRIER SHIFT Less than 1% at 95% negative modulation at
1 kHz.
TYPE OF MODULATION Pulse Width Modulation of L+R envelope with
integrated C-QUAM AM stereo. An RF input
connector is also provided for an external stereo
exciter.
OPERATING MODES Stereo, mono L+R, mono L, mono R, by local or
remote control.
MODULATION CAPABILITY
AM-1A Greater than 145% peak positive capability at
1100 watts. 130% into a 1.5 : 1 VSWR.
AM-500A Greater than 145% peak positive capability at
500 watts. 130% into a 1.3 : 1 VSWR.
MODULATION INPUT Peak reading, color coded, LED bar graph display
INDICATION with an autorange feature for monitoring positive
or negative input levels of four different audio
channels (L/R or L+R/L-R).
AUDIO INPUT LEVEL +10 dBm, ±1 dB, L+R (or mono) to produce 100%
L+R envelope modulation. Other input levels can
be accommodated.

1-5
TABLE 1-1. ELECTRICAL CHARACTERISTICS
(Sheet 2 of 3)
PARAMETER SPECIFICATION
AUDIO INPUT IMPEDANCE 600 Ohms. Inputs are balanced, transformerless,
and resistive with passive RFI filtering. Other
impedances can be accommodated.
AUDIO FREQUENCY RESPONSE
(MONOPHONIC)
AM-1A ±0.5 dB, 20 Hz to 10 kHz at 90% negative
modulation (linear phase mode). +0.1 dB
-3 dB, 20 Hz to 10 kHz at 90% negative
modulation, standard configuration. 90%
negative modulation referenced at 1 kHz (9 dBm).
AM-500A ±1.0 dB, 20 Hz to 10 kHz at 90% negative
modulation (linear phase mode). +0.1 dB
-3 dB, 20 Hz to 10 kHz at 90% negative
modulation, standard configuration. 90%
negative modulation referenced at 1 kHz (9 dBm).
AUDIO HARMONIC DISTORTION
AM-1A Mono Less than 0.8%, 20 Hz to 10 kHz at 1 kW.
Less than 1.5%, 20 Hz to 10 kHz at 500 W.
Less than 2.0%, 20 Hz to 10 kHz at 250 W.
Less than 3.0%, 20 Hz to 10 kHz at 100 W.
The mono audio harmonic distortion
specifications are referenced to an audio input
level which generates 90% modulation at 1 kHz
(9 dBm).
AM-1A Stereo Less than 1.5% at 50% single channel
modulation, 50 Hz to 10 kHz at rated power.
AM-500A Mono Less than 1.2%, 20 Hz to 10 kHz at 500 Watts.
The mono audio harmonic distortion
specifications are referenced to an audio input
level which generates 90% modulation at 1 kHz
(9 dBm).
AM-500A Stereo Less than 2.0% at 50% single channel
modulation, 50 Hz to 10 kHz at rated power.
INTERMODULATION DISTORTION 1.2% or less at 1:1 ratio. 1.7% or less at 4:1 ratio.
(MONO) 60/7000 Hz SMPTE standards with 85%
modulation at rated power.
CCIF INTERMODULATION 1.0% or less at 1:1 ratio. 4 kHz/5 kHz with 85%
DISTORTION (MONO) modulation at rated power.
TRANSIENT INTERMODULATION 1.0% or less at 4:1 ratio. 2.96 kHz square wave
DISTORTION (MONO) 8 kHz sinewave with 85% modulation at rated
power.

1-6
TABLE 1-1. ELECTRICAL CHARACTERISTICS
(Sheet 3 of 3)
PARAMETER SPECIFICATION
INCIDENTAL PHASE 30 dB below equivalent 100% L-R C-QUAM
MODULATION modulation 50 Hz to 10 kHz at rated power.
(STEREOPHONIC) Measured with an audio input level which
generates 95% negative L+R envelope modulation
at 1 kHz (9.5 dBm).
STEREO SEPARATION
AM-1A -30 dB or greater, 50 Hz to 10 kHz. Measured
with 50% single channel modulation into a 50
ohm resistive load at rated power.
AM-500A -25 dB or greater, 50 Hz to 10 kHz. Measured
with 50% single channel modulation into a 50
ohm resistive load at rated power.
SQUAREWAVE OVERSHOOT
Mono 0.1% or less at 400 Hz, 90% modulation with high
frequency boost disabled.
Stereo 1% or less at 400 Hz, 50% single channel modula-
tion with high frequency boost disabled.
SQUAREWAVE TILT Less than 1% at 40 Hz. Less than 1.5% at 20 Hz.
Measured with 90% negative modulation.
NOISE
Mono Greater than 65 dB below a reference level equiva-
lent to 100% negative modulation in a 22 Hz to
30 kHz bandwidth, unweighed.
Stereo Greater than 55 dB below a reference level equiva-
lent to 100% negative modulation of either left or
right channel in a 22 Hz to 30 kHz bandwidth,
unweighed.
AC INPUT VOLTAGE 196V to 252V ac, 50/60 Hz, single phase. Includes
built-in MOVs for surge suppression.
AC POWER CONSUMPTION
AM-1A 1.37 kW, no modulation of 1 kW carrier.
2.05 kW, 100% sinusoidal modulation of 1 kW
carrier.
Measured at 1 kW into a 50 Ohm resistive load at
220V ac.
AM-500A 830 watts, no modulation of 500 watt carrier.
1.25 kW, 100% sinusodial modulation of 500 Watt
carrier. Measured at 500 watts into a 50 Ohm
resistive load at 220V ac.

1-7
TABLE 1-2. PHYSICAL AND ENVIRONMENTAL CHARACTERISTICS
(Sheet 1 of 2)
PARAMETER SPECIFICATION
OVERALL EFFICIENCY
AM-1A 73% or greater, 100% sinusoidal modulation of
carrier, ac line to RF output. Measured at 1 kW
into a 50 Ohm resistive load at 220V ac.
AM-500A 60% or greater, 100% sinusodial modulation of
carrier, ac line to RF output. Measured at 500
Watts into a 50 Ohm resistive load at 220V ac.
SAFETY Meets IEC 215 specifications.
OUTPUT POWER Less than 1% change in output power with
variation of ac line voltage from 196-252 volts.
METERING
AM-1A Output Forward Power: 1) High scale - 0 to 1200
watts and 2) Low scale - 0 to 300 watts. Output
Reflected Power: 1) High scale - 0 to 120 watts
and 2) Low scale - 0 to 30 watts. Ac Line
Voltage: Scale - 150 to 300 volts. AM-1A forward
power meter complies with FCC rule 73.1215(a)
within the 60 watt to 1100 watt range.
AM-500A Output Forward Power: 1) High scale - 0 to 600
watts and 2) Low scale - 0 to 150 watts. Output
Reflected Power: 1) High scale - 0 to 60 watts
and 2) Low scale - 0 to 12 watts. Ac Line
Voltage: Scale - 150 to 300 volts. AM-500A
forward power meter complies with FCC rule
73.1215(a) within the 30 watt to 500 watt range.
RF MONITORING PROVISIONS 2 volts RMS nominal RF output sample into a 50
Ohm input. Adjustable from the output network
chassis rear panel for each of the five preset
power levels.
REMOTE INTERFACE Built-in interface for most control and monitoring
systems.
PHYSICAL
DIMENSIONS
ECU Chassis Width: 19.0 Inches (48.3 cm).
Height: 10.5 Inches (26.7 cm).
Depth: 14.4 Inches (36.6 cm).
Output Network Chassis Width: 19.0 Inches (48.3 cm).
Height: 14 Inches (35.6 cm).
Depth: 27.1 Inches (68.8 cm).
WEIGHT 90.6 Pounds (41.1 kg), unpacked.

1-8
TABLE 1-2. PHYSICAL AND ENVIRONMENTAL CHARACTERISTICS
(Sheet 2 of 2)
PARAMETER SPECIFICATION
CUBAGE 7.3 Ft3(0.21 m3).
ENVIRONMENTAL
COOLING Low velocity air with cleanable filters. 250 Cubic
Feet Per Minute (7.08 m3/min).
OPERATING TEMPERATURE 0°to 50°C (+32°to +122°F).
OPERATING HUMIDITY 0 to 95% (non-condensing).
MAXIMUM ALTITUDE
60 Hz Models 0 to 10,000 feet above sea level (0 to 3048 Meters).
50 Hz Models 0 to 7,500 feet above sea level (0 to 2286 Meters).
NOTE - AM-500A - All specifications measured at 500 watts into a 50 ohm resistive load using
Broadcast Electronics AS-10 modulation monitor.
AM-1A - All specifications measured at 1100 watts into a 50 ohm resistive load using
Broadcast Electronics AS-10 modulation monitor.