UBS Axcera 334B User Manual

INSTRUCTION MANUAL

334B

2000 WATT VHF LOW BAND

TRANSMITTER

AXCERA, LLC

103 FREEDOM DRIVE P.O. BOX 525 LAWRENCE, PA 15055-0525 USA

[phone] • FAX [phone]

www.axcera.com • [e-mail]

2000-Watt VHF Low Band Transmitter Table of Contents

TABLE OF CONTENTS

CHAPTER 1 INTRODUCTION

SECTION PAGE

1.1 Manual Overview ............................................................................ 1-1

1.2 Assembly Designation Procedure ........................................................ 1-1

1.3 Safety........................................................................................... 1-1

1.4 Contact Information......................................................................... 1-2

1.5 Material Return Procedure................................................................. 1-2

1.6 Limited One-Year Warranty for Axcera Pro ducts .................................... 1-3

CHAPTER 2 SYSTEM DESCRIPTION, MAINTENANCE & REMOTE CONTROL
CONNECTIONS

2.1 System Overview............................................................................ 2- 1

2.2 Control and Status of Transmitter....................................................... 2-4

2.2.1 VHF Exciter Tray .................................................................... 2-5

2.2.2 VHF Amplifier Tray.................................................................. 2-7

2.3 Maintenance.................................................................................. 2-8

2.4 Input Connections........................................................................... 2-9

2.5 Customer Remote Control Connections.......................................... 2-9

CHAPTER 3 INSTALLATION AND SETUP PROCEDURES

3.1 Site Considerations.......................................................................... 3-1

3.2 Unpacking the Cabinet and Trays ....................................................... 3-4

3.3 Installing the Cabinet and Trays......................................................... 3-5

3.4 Setup and Operation Procedures ........................................................ 3-6

CHAPTER 4 CIRCUIT DESCRIPTIONS

4.1 Low-Band VHF Exciter...................................................................... 4-1

4.1.1 Aural IF Synthesizer Board, 4.5 MHz .......................................... 4-1

4.1.2 Sync Tip Clamp/Modulator Board ............................................... 4-3

4.1.3 Delay Equalizer Board ............................................................. 4-6

4.1.4 IF Carrier Oven Oscillator Board ................................................ 4-7

4.1.4.1 IF VCXO Board .............................................................. 4-8

4.1.5 ALC Board, NTSC.................................................................... 4-9

4.1.6 IF Phase Corrector Board ........................................................4-15

4.1.7 VHF Mixer/Amplifier Enclosure Assembly ....................................4-17

4.1.7.1 x2 Multiplier Board ........................................................4-17

4.1.7.2 VHF Filter/Mixer Board ...................................................4-18

4.1.7.3 Low Band VHF Filter/Amplifier Board .................................4-18

4.1.8 Transmitter Control Board .......................................................4-19

4.1.9 Visual/Aural Metering Board .....................................................4-24

4.1.10 Channel Oscillator Assembly, Dual Oven...................................4-25

4.1.10.1 VCXO Channel Oscillator Assembly, Dual Oven ..................4-26

4.1.11 (Optional) EEPROM FSK Identifier Board ...................................4-26

4.1.12 (Optional) IF Attenuator Board ...............................................4-27

4.2 VHF Low-Band Amplifier Trays..........................................................4-27

4.3 3 Way Combiner Assembly..............................................................4-31

334B, Rev. 0 i June 29, 2004

2000-Watt VHF Low Band Transmitter Table of Contents

TABLE OF CONTENTS (continued)

SECTION PAGE

4.4 Harmonic Filter, Bandpass Filter and Coupler Assembly..........................4-31

CHAPTER 5 DETAILED ALIGNM ENT PROCEDURES

5.1 VHF Low-Band Exciter Tray with Baseband Video and Audio Inputs........... 5-1

5.2 VHF Exciter Tray with 4.5-MHz Composite Input Kit ............................... 5-2

5.3 VHF Exciter Tray with Either Baseband or 4.5-MHz Composite Input.......... 5-2

5.4 IF Phase Corrector Adjustment .......................................................... 5-3

5.5 Linearity Corrector Adjustment .......................................................... 5-3

5.6 Low Band VHF Amplifier Trays ........................................................... 5-4

5.6.1 AGC Control Board .................................................................. 5-5

5.6.2 Phase Shifter Board ................................................................ 5-5

5.6.3 VHF Filter/Amplifier Board........................................................ 5-5

5.6.4 VHF Low Band Amplifier Board .................................................. 5-5

5.6.5 Overdrive Protection Board....................................................... 5-5

5.6.6 3-Way Splitter Board ............................................................... 5-6

5.6.7 VHF Low Band Pallet ............................................................... 5-6

5.6.8 3-Way Combiner Board ............................................................ 5-6

5.6.9 Calibration of the Visual + Aural Output Power and VSWR Cutback... 5-6

5.7 Phase and Gain Adjustment of Multiple VHF Amplifier Trays..................... 5-7

5.8 Calibration of the Forward Output Level of the Transmitter...................... 5-8

5.9 Calibration of the Reflected Output Level of the Transmitter..................... 5-8

5.10 3-Way Combiner Assembly.............................................................. 5-9

5.11 Bandpass Filter Assembly................................................................ 5-9

5.12 Complete Board Level Alignment of the VHF Exciter ............................. 5-9

5.12.1 (Optional) 4.5-MHz Composite Input Kit .................................... 5-9

5.12.2 Delay Equalizer Board............................................................ 5-9

5.12.3 Composite 4.5-MHz Filter Board ..............................................5-10

5.12.4 (Optional) 4.5-MHz Bandpass Filter Board.................................5-10

5.12.5 IF Carrier Oven Oscillator Board..............................................5-10

5.12.6 Sync Tip Clamp/Modulator Board ............................................5-10

5.12.7 Aural IF Synthesizer Board, 4.5 MHz ........................................5-12

5.12.8 ALC Board (Part 1 of 2) .........................................................5-13

5.12.9 IF Phase Corrector Board .......................................................5-14

5.12.10 ALC Board, NTSC (Part 2 of 2)..............................................5-14

5.12.11 Channel Oscillator Board, Dual Oven ......................................5-15

5.12.12 x2 Multiplier Board .............................................................5-15

5.12.13 VHF Filter/Mixer Board ........................................................5-16

5.12.14 VHF Low-Band Filter/Amplifier Board......................................5-16

APPENDICES

APPENDIX A SYSTEM SPECIFICATIONS
APPENDIX B SAMPLE LOG REPORT SHEET AND TYPICAL READINGS
APPENDIX C ASSEMBLY DRAWINGS AND PARTS LISTS
APPENDIX D SUBASSEMBLY DRAWINGS AND PARTS LISTS

334B, Rev. 0 ii June 29, 2004

2000-Watt VHF Low Band Transmitter Table of Contents

LIST OF FIGURES

FIGURE PAGE

3-1 1 kW Minimum Ventilation Configuration ....................................... 3-4

3-2 Chassis Trak Cabinet Slides ........................................................ 3-5

5-1 Waveform..............................................................................5-11

334B, Rev. 0 iii

2000-Watt VHF Low Band Transmitter Table of Contents

LIST OF TABLES

TABLE PAGE

2-1 334B Trays and Assemblies ........................................................ 2-1

2-2 VHF Exciter Tray Meters ............................................................. 2-5

2-3 VHF Exciter Tray Switches.......................................................... 2-6

2-4 VHF Exciter Tray Fault Indicators ................................................. 2-6

2-5 VHF Exciter Tray Samples .......................................................... 2-6

2-6 VHF Amplifier Tray Switches....................................................... 2-7

2-7 VHF Amplifier Tray Fault Indicators .............................................. 2-8

2-8 VHF Amplifier Tray Control Adjustments........................................ 2-8

2-9 VHF Amplifier Tray Sample ......................................................... 2-8

2-10 334B Customer Remote Control Connections .........................2-10

4-1 VHF Amplifier Tray Boards and Assemblies ...................................4-27

5-1 ALC Board LEDs ......................................................................5-13

334B, Rev. 0 iv

2000-Watt VHF Low Band Transmitter Chapter 1, Introduction

Chapter 1

Introduction

This manual explains the installation,
setup, alignment, and maintenance
procedures for the 334B 2000-watt solid
state VHF Low Band transmitter. It is
important that you read all of the
instructions, especially the safety
information in this chapter, before you
begin to install or operate the unit.

1.1 Manual Overview

This instruction manual is divided into
five chapters and supporting appendices.
Chapter 1, Introduction, contains
information on the assembly numbering
system used by Axcera, safety, contact
information, return procedures, and
warranties. Chapter 2, System
Description, Maintenance and Remote
Control Connections, describes the
transmitter and includes discussions on
system control and status indicators,
maintenance and remote control
connections. Chapter 3 Installation and
Set Up Procedure, explains how to
unpack, install, setup, and operate the
transmitter. Chapter 4, Circuit
Descriptions, contains a detailed
discussion of the circuits and boards that
make up the 334B. Chapter 5, Detailed
Alignment Procedures, provides
information on adjusting the system and
trays to achieve peak operation of the
transmitter and assemblies. The
appendices contain system
specifications, a sample log sheet, typical
operational readings, interconnects,
schematics, assembly and subassembly
drawings and parts lists.

1.2 Assembly Designation Procedure

Axcera has assigned assembly numbers,
such as Ax (x=1,2,3…), to all assemblies,
trays, subassemblies, and boards that
make up the 334B. The assembly
numbers are referenced to in the text of
this manual and shown on the block
diagrams and interconnect drawings

provided in the appendices. These
supporting documents are arranged in
increasing numerical order in the
appendices. Section titles in the text for
assembly, tray descriptions and
alignment procedures also indicate the
associated drawing(s) and the relevant
appendix that contains the drawing.
Sections describing vendor-supplied
items, such as meters and power
supplies, do not contain this information.

1.3 Safety

The transmitters manufactured by Axcera
are designed for ease of operation and
repair while providing protection from
electrical and mechanical hazards. Listed
throughout the manual are notes,
cautions, and warnings concerning
possible safety hazards that may be
encountered while operating or servicing
the transmitter. Please review these
warnings and familiarize yourself with the
operation and servicing procedures
before attempting to maintain or repair
the transmitter.

Read All Instructions – All of the
operating and safety instructions should
be read and understood before operating
this equipment.

Retain Manuals – An instruction manual
provided with the transmitter should be
retained at the transmitter site for future
reference. Axcera provides two
instruction manuals for this purpose; one
manual can be left at the office while the
other can be kept at the site.

Heed all Notes, Warnings, and
Cautions – The avoid injury or damage

to the equipment, all of the notes,
warnings, and cautions listed in this
safety section and throughout the
manual must be followed.

334B, Rev. 0 1-1

2000-Watt VHF Low Band Transmitter Chapter 1, Introduction

Follow Instructions – All of the
operating and use instructions for the
transmitter should be followed.

Cleaning – Unplug or otherwise
disconnect all power from the equipment
before cleaning. Do not use liquid or
aerosol cleaners as damage to silk
screens may occur. Use a damp cloth for
cleaning.

Ventilation – Openings in the cabinets
and tray front panels are provided for
ventilation. To ensure reliable operation
of the transmitter, and to protect the unit
from overheating, these openings must
not be blocked and cleaned regularly.

Servicing – Do not attempt to service
this product yourself until becoming
familiar with the equipment. If in doubt,
refer all servicing questions to qualified
Axcera service personnel.

Replacement Parts – When
replacement parts are needed, use the
replacement part numbers as given on
the parts lists included in this manual, in
Appendix C or Appendix D. If other parts
are used, be sure that the parts have the
same functional and performance
characteristics as the original part.
Unauthorized substitutions may result in
fire, electric shock, or other hazards.
Please contact the Axcera field service
department if you have any quest ions
regarding service or replacement parts.

1.4 Contact Information

The Axcera Field Service Department can
be contacted by phone at (724) 873-
8100 or by fax at [phone].

Before calling Axcera, please be prepared
to supply the Axcera technician with
answers to the following questions. This
will save time and help ensure the most
direct resolution to the problem.

1. What are the Customers’ Name and
call letters?

2. What are the model number and
type of transmitter?

3. Is the transmitter digital or analo g?

4. How long has the transmitter been
on the air? (Approximately when
was the transmitter installed.)

5. What are the symptoms being
exhibited by the transmitter?
Include the status as read on the
LCD display, if present. Also record
the status of any LEDs lo cated on
the front panels of the Trays.
Include all meter readings from the
trays.

1.5 Material Return Procedure

To insure the efficient handling of
equipment or components that have been
returned for repair, Axcera requests that
each returned item be accompanied by a
Material Return Authorization Number
(MRA#).

An MRA# can be obtained from any
Axcera Field Service Engineer by
contacting the Axcera Field Service
Department at [phone] or by fax
at [phone]. This procedure
applies to all items sent to the Field
Service Department regardless of
whether the item was originally
manufactured by Axcera.

NOTE: To prevent damage to the product
during shipping, Axcera will supply a
shipping container to the customer upon
request.

When equipment is sent to the field on
loan, an MRA# is included with the unit.
The MRA# is intended to be used when
the unit is returned to Axcera. All
shipping material should be retained for
the return of the unit to Axcera.

Replacement assemblies are also sent
with an MRA# to allow for the proper
routing of the exchanged hardware.
Failure to close out this type of MRA# will
normally result in the customer being
invoiced for the value of the loaner item
or the exchange assembly.

334B, Rev. 0 1-2

2000-Watt VHF Low Band Transmitter Chapter 1, Introduction

When shipping an item to Axcera, please
include the MRA# on the packing list and
on the shipping container. The packing
list should also include contact
information and a brief description of why
the unit is being returned.

Please forward all MRA items to:

Axcera, LLC
103 Freedom Drive
P.O. Box 525
Lawrence, PA 15055-0525 USA

For more information concerning this
procedure, call the Axcera Field Service
Department.

Axcera can also be contacted through
e-mail at [e-mail] and on the
Web at www.axcera.com.

1.6 Limited One-Year Warranty for
Axcera Products

Axcera warrants each new product that
it has manufactured and sold against
defects in material and workmanship
under normal use and service for a
period of one (1) year from the date of
shipment from Axcera's plant, when
operated in ac cordance with Axcera's
operating instructions. This warranty
shall not apply to tubes, fuses,
batteries, or bulbs.

Warranties are valid only when and if
(a) Axcera receives prompt written
notice of breach within the period of

warranty, (b) the defective product is
properly packed and returned by the
buyer (transportation and insurance
prepaid), and (c) Axcera determines, in
its sole judgment, that the product is
defective and not subject to any misuse,
neglect, improper installation,
negligence, accident, or (unless
authorized in writing by Axcera) repair
or alteration. Axcera's exclusive liability
for any personal and/or property
damage (including direct, consequential,
or incidental) caused by the breach of
any or all warranties, shall be limited to
the following: (a) repairing or replacing
(in Axcera's sole discretion) any
defective parts free of charge (F.O.B.
Axcera’s plant) and/or (b) crediting (in
Axcera's sole discretion) all or a portion
of the purchase price to the buyer.

Equipment furnished by Axcera, but not
bearing its trade name, shall bear no
warranties other than the special hours ­of-use or other warranties extended by
or enforceable against the manufacturer
at the time of delivery to the buyer.

NO WARRANTIES, WHETHER
STATUTORY, EXPRESSED , OR
IMPLIED, AND NO WARRANTIES OF
MERCHANTABILITY, FITNESS FOR
ANY PARTICULAR PURPOSE, OR
FREEDOM FROM INFRINGEMENT,
OR THE LIKE, OTHER THAN AS
SPECIFIED IN PATENT LIABILITY
ARTICLES, AND IN THIS ARTICLE,
SHALL APPLY TO THE EQUIPMENT
FURNISHED HEREUNDER.

334B, Rev. 0 1-3

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

Chapter 2

System Description, Maintenance & Remote Control Connections

The 334B is a complete 2000-watt VHF
Low Band solid state internally diplexed
television transmitter that operates at a
nominal visual output power of 2000
watts peak sync and an average aural
output power of 200 watts, at an A/V

Table 2-1. 334B Trays and Assemblies

MAJOR ASSEMBLY

DESIGNATOR

A2 AC distribution block
A4 VHF L.B. exciter

A6, A7 & A11 Three VHF amplifier trays 1304363

A8 VHF combiner assembly 1065241
A13 Harmonic filter 1304390
A14 Bandpass filter assembly 1304388
A12 Remote interface assembly 1083510

(Optional)

A25

VHF L.B. Exciter Tray

The (A4) VHF L.B. exciter tray (1070820)
operates using baseband audio and video
inputs to produce a diplexed, modulated,
and on-channel frequency visual + aural
RF output.

NOTE: If your transmitter contains a
precise frequency kit, a precise frequency
control tray provides the PLL circuits that
connect to the VHF exciter tray w/precise
frequency (1304463) for precise channel
oscillator frequency control. Refer to the
334B precise frequency control system
instruction manual for information on the
precise frequency control tray and
system.

Aural IF Synthesizer Board

The baseband audio, either balanced at
TB1 or composite at J6, and the
subcarrier audio at J4, if present, connect
from the rear of the VHF exciter to (A4)
the aural IF synthesizer board (1265-

TRAY/ASSEMBLY NAME DRAWING NUMBER

Precise Frequency Control Tray

ratio of 10 dB, 10% sound, or 100 watts
at 13 dB, 5% sound.

2.1 System Overview

The 334B (1304407) is made up of the
trays and assemblies listed in Table 2-1.

1070820 or

1304463 w/Precise Frequency

1294-1153(+), 1294-1154(0)

or 1294-1155(-)

1303). The board amplifies and controls
the levels of the three possible audio
inputs and provides a single audio
output. A 4.5-MHz CW signal is
generated using a voltage controlled
oscillator (VCO), onto which the audio is
modulated. This produces the modulated

4.5 MHz output of the board that
connects to the sync tip modulator board.
The board also contains a phase lock loop
(PLL) circuit that maintains the precise

4.5-MHz separation between the aural
(41.25 MHz) and the visual (45.75 MHz)
IF frequencies

Sync Tip Clamp/Modulator Board

The baseband video connects from J1 on
the rear of the VHF exciter to (A5) the
sync tip clamp/modulator board (1265-

1302). The sync tip clamp/modulator
board takes the video, amplifies it,
provides a sync tip clamp circuit and
modulates the video with a 45.75 MHz IF
generated by the IF carrier oven
oscillator or IF VCXO board. The audio

334B, Rev. 0 2-1

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

modulated 4.5 MHz IF, from the aural IF
synthesizer board, is mixed with the

45.75 MHz CW to produce a modulated

41.25 MHz aural IF output. The video
modulated 45.75 MHz is then diplexed
with the audio modulated 41.25 MHz to
produce the combined Visual IF + Aural
IF output of the board that connects to
the ALC board.

4.5 MHz Composite Input Kit

NOTE: If your transmitter does not
contain the 4.5 MHz composite input kit,
the following paragraph description does
not pertain. If the (optional) 4.5-MHz
composite input kit is purchased, the 4.5­MHz composite input or the baseband
video and audio inputs are used. The
switching between the inputs is
accomplished by a relay mounted on the
sync tip clamp modulator board that is
controlled by a baseband select. The
baseband select controls a relay that
selects either the 4.5 MHz generated
from the baseband inputs or from the

4.5-MHz composite input. To operate the
transmitter with the (optional) 4.5-MHz
composite input kit using baseband
inputs, the baseband video must be
connected to J1 or J2, the baseband
audio must be connected to the proper
input jack, and a baseband select must
be connected from J7-6 and J7-7. To
operate the transmitter with the
(optional) 4.5-MHz composite input kit
using the 4.5-MHz composite input, the

4.5-MHz composite input must be
connected to J1 or J2 and the baseband
select must be removed from J7-6 and
J7-7.

IF Carrier Oven Oscillator Board

NOTE: If the precise frequency kit is
present in your transmitter, the IF VCXO
Board (1248-1131) will be used.

The IF carrier oven oscillator (1191-

1404) or the IF VCXO board generates
the 45.75 MHz visual IF CW signal that
connects to the sync tip clamp/modulator
board.

ALC Board

The (A8) automatic level control (ALC)
board (1265-1305) provides the ALC and
amplitude linearity correction of the

45.75 MHz + 41.25 MHz IF signal. The
ALC circuit adjusts the level of the
combined IF signal through the board
that controls the output power of the
transmitter. The level controlled
combined IF output of the ALC board
connects to the filter/mixer board.

VHF L.B. Filter/Mixer Board

The (A11-A2) VHF filter/mixer board
(1153-1101) is made up of three
separate circuits. The on channel
frequency RF output of the x2 multiplier
board connects to a filter and amplifier
circuit before it is connected to the mixer
stage. The combined 41.25 MHz + 45.75
MHz IF from the ALC board also connects
to the mixer stage. The RF output of the
mixer is filtered and amplified in the final
circuit before it is connected to the VHF
filter amplifier board.

X2 Multiplier Board

The (A11-A1) x2 multiplier board (1172-

1111) multiplies the frequency of the RF
from the channel oscillator by a factor of
two using a broadband frequency doubler
circuit. The RF on channel frequency
output of the board connects to the
filter/mixer board.

VHF Low Band Filter Amplifier Board

The VHF low band filter/amplifier board
(1064251) is made up of two separate
circuits. The RF output of t he filter/mixer
board is connected to a filter circuit tuned
for best response on the channel
frequency. The filtered RF is then
connected to an amplifier circuit with a
manual gain control. The output of the
board connects to J15, the RF output jack
located on the rear of the VHF exciter
tray

334B, Rev. 0 2-2

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

Channel Oscillator Board

NOTE: If the precise frequency kit is
present in your transmitter, the VCXO
Channel Oscillator Board (1145-1204)
will be used.

The channel oscillator board (1145-1201)
or VCXO board generates a stable
frequency reference signal of
approximately 100 MHz. The output
connects to the x2 multiplier board.

Transmitter Control Board

The (A17) transmitter control board
(1265-1311) provides system control
functions and the operational LED
indications, which can be viewed on the
front panel of the transmitter. The main
control functions are the
Operate/Standby and Auto/Manual
selections. When the transmitter is
switched to Operate, the board supplies
the enables to the three external VHF
amplifier trays. The board also performs
the automatic switching of the
transmitter to Standby upon the loss of
the video input when the transmitter is in
Automatic.

Visual/Aural Metering Board

The (A19) visual/aural metering board
(1265-1309) provides det ected outputs
of the visual, aural, and reflected output
samples that are used for monitoring on
the front panel meter. These readings are
attained from the forward power and the
reflected power samples from the output
coupler assembly of the transmitter.

4 Way Power Splitter

The RF output of the VHF exciter is split
four ways in (A5) the 4-way power
splitter assembly (ZFSC-4-3BNC). Only
three of the outputs are used in this
configuration, the fourth is terminated.

VHF Low Band Amplifier Tray

The outputs of the splitter feed the three
(A6, A7 and A11) VHF amplifier trays
(1304363). Each tray amplifies the RF
signals to approximately 750 watts peak
of sync visual + aural.

In the VHF amplifier tray, a forward
power sample and a reflected power
sample from the combiner board are
connected to the AGC control board that
provides peak-detected samples that are
monitored on the front panel meter of
the tray.

3 Way VHF Combiner Assembly

The outputs of the three VHF amplifier
trays are combined in (A8) the 3 way
VHF combiner that provides
approximately 2100 watts peak of sync
output.

Harmonic and Bandpass Filters
The output of the combiner assembly is

connected to (A13) a harmonic filter and
(A14) a bandpass filter assembly. The
harmonic and bandpass filters are tuned
to provide a high out -of-band rejection of
unwanted products.

Output Coupler Assembly
The filtered signal is connected to the

(A16) coupler assembly, which provides
a forward and a reflected power sample
to the visual/aural metering board
mounted in the VHF exciter. The forward
sample is processed to provide peak
detected visual and aural power output
samples to the transmitter control board
in the VHF exciter. The reflected power
sample is also peak detected and wired
to the transmit ter control board. The
transmitter control board connects the
visual, aural, and reflected power output
samples to the front panel meter for
visual monitoring of the system
operation.

334B, Rev. 0 2-3

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

2.2 Control and Status of Transmitter
Control and status information for the

transmitter is provided by the meter and
LED indicators on the front panel of the
VHF exciter. The switches and LED
indicators are part of the (A17)
transmitter control board that is mounted
so that the switches and LEDs are
operated or viewed from the front panel
of the VHF exciter.

Switch S1 is an Operate/Standby switch
that controls the output of the
transmitter by providing the Enables
that, when the transmitter is in Operate,
are needed to turn on the switching
power supplies in the three VHF amplifier
trays. When the transmitter is in
Operate, the green LED DS2, located on
the front panel of the VHF exciter. When
it is in Standby, the amber LED DS1 is
on. If the transmitter does not switch to
Operate when S1 is switched to Operate,
check that a dummy jumper plug is
connected to (A12-J9 at pins 21 and 22)
on the remote interface panel. It must
be present for the transmitter to operate.
If the interlock is present, the green LED
DS5, mounted on the transmitter control
board, will be lit.

NOTE: If the remote interface panel is
not present in your transmitter the
dummy jumper plug must be present on
J11, with a jumper between pins 23 and
24, located on the back of the VHF
exciter tray. The jumper provides the
interlock needed for the transmitter to
operate. If the interlock is present, the
green LED DS5, mounted on the
transmitter control board, will be lit.

Switch S2 is an Automatic/Manual switch
that controls the operation of the
transmitter by the presence of the video
input signal. When the switch is in
Automatic, the green LED DS3 is lit and,
if the video input signal to the
transmitter is lost, the transmitter will
automatically switch to Standby. When
the video input signal returns, the
transmitter will automatically switch back
to Operate. In Manual, the amber LED
DS4 is lit and the operation of the
transmitter is controlled by the front
panel switches. During normal operation
of the transmitter, switch S2 should be in
the Auto position. The front panel of the
VHF exciter also has LEDs that indicate a
Video Fault (red LED DS9) and VSWR
Cutback (amber LED DS7).

334B, Rev. 0 2-4

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

2.2.1 VHF Exciter Tray (A4)

Table 2-2. VHF Exciter Tray Meters

METER FUNCTION

This meter reads power in terms of a percentage of the calibrated
output power level on the upper scale. The voltage level or
frequency level is read on one of the bottom two scales. A full­scale reading on the top scale is 120%. 100% is equivalent to the
full-rated 2000 watts peak of sync visual. The meter also reads %
Aural Power, % Exciter Power, % Reflected Power, audio levels,
video levels, and the ALC reading.

With Switch S3 in Position Display

Selects the desired ALC voltage
reading, % Exciter Power,

Switch S3, Meter

Audio

(0 to 100 kHz)

Meter (A4-A18)

ALC

(0 to 10 volts)

% Exciter

(0 to 120)

% Aural Power

(0 to 120)

% Visual Power

(0 to 120)

% Reflected

(0 to 120)

Video

(0 to 1 volt)

% Reflected Power, % Visual
Power, % Aural Power, video
level, or audio level.
Reads the audio level, ±25 kHz
balanced or ±75 kH composite,
on the 0 to 10 scale. Will indicate
baseband audio, if it is connected
to the transmitter, even with the
(optional) video + 4.5-MHz SCA
input selected.
Reads the ALC voltage level,
.8 VDC, on the 0 to 10 scale.
Reads the % Exciter Output
Power Level needed to attain
100% output of the transmitter
on the top scale.
Reads the % Aural Output Power
of the transmitter,
100% = 200 watts at 10 dB A/V
ratio, on the top scale.
Reads the % Visual Output Power
of the transmitter,
100% = 2000 watts peak of sync,
on the top scale.
Reads the % Reflected Output
Power, <5%, on the top scale.
Reads the video level, at white,
on the bottom 0 to 10 scale.

334B, Rev. 0 2-5

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

Table 2-3. VHF Exciter Tray Switches

SWITCH FUNCTION

The momentary switch S1 applies a ground to K1, a latching
relay on the transmitter control board. K1 will switch either

S1

Transmitter

Operate/Standby

S2
Mode Select
Auto/Manual

R1

Power Adjust

Table 2-4. VHF Exciter Tray Fault Indicators

INDICATOR DESCRIPTION

DS9

Video Loss

(Red)

DS7

VSWR Cutback

(Amber)

SAMPLE DESCRIPTION

f(IF)

f(IC)

f(s)

Exciter O/P

Transmitter O/P

to Operate or to Standby depending on which direction S1 is
pushed. When switched to Operate, the low, Enable
commands are applied to the VHF amplifier trays. These
Enables will turn on the VHF amplifier trays. The opposite
occurs when the switch is turned to Standby.
The momentary switch S2 applies a ground to K2, a latching
relay on the transmitter control board. K2 will switch the
transmitter to Automatic or Manual depending on which
direction S2 is pushed. In Automatic, the video fault
command from the ALC Board will control the operation of
the transmitter. The transmitter will switch to Standby, after
a slight delay, if the input video is lost and will switch back to
Operate, quickly, when the video is restored. In Manual, the
transmitter is controlled by the operator using the front panel
Operate/Standby switch or by remote control.
The 5 kΩ pot (A20) sets the ALC level on the ALC board that
controls the output power of the transmitter.

Indicates that the input video to the transmitter has been
lost. The fault is generated on the ALC board in the VHF
exciter tray.
Indicates that the reflected power level of the transmitter has
increased above 20%. This automatically cuts back the
output power level to 20%. The fault is generated on the
transmitter control board in the VHF exciter tray.

Table 2-5. VHF Exciter Tray Samples

A sample of the visual IF that is taken from the sample jack
on the IF carrier oven oscillator board.
A sample of the intercarrier signal that is taken from the
sample jack on the aural IF synthesizer board.
A sample of the channel oscillator output that is taken from
the sample jack of the channel oscillator assembly.
An output power sample of the exciter that is take n from the
VHF filter/amplifier board.
A forward power sample of the transmitter that is taken from
the output coupler assembly through the visual/aural
metering board.

334B, Rev. 0 2-6

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

2.2.2 VHF Amplifier Tray (A6, A7 & A11)

Table 2-6. VHF Amplifier Tray Switches

SWITCH FUNCTION

CB1

On/Off Circuit Breaker

S1

Switch, Meter

S2

Switch, Meter

Switches 220 VAC through a 15-amp circuit breaker-type
protection device. The switch lights if AC is present. The
AC is applied to the switching power supply in the tray.

Selects the desired % Visual Forward Output Power, %
Visual Reflected Power reading, AGC Voltage, Power Supply
Voltage, or Current

With Switch S1 in

Position

Reads the % Forward Output

% Forward

% Refl (Reflected)

AGC Voltage

Power Supply

Current

Selects the current of the transistor devices on the high
band amplifier boards. S1 must be in the Current position.

With Switch S2 in

Position

I1

I2

I3

ID

Power of the tray (100%= 750
watts peak of sync + aural)
Reads the % Reflected Output
Power (<5%)
Reads the AGC level of the tray
(1 to 3 VDC)
Reads the voltage from the
switching power supply
(+30 VDC)
Uses Switch S2 to indicate the
current of transistor devices

Reads the current of (A3-A1) the
low band amplifier board (idling
current=1.8 amps and operating
current=12-13 amps, black
picture)
Reads the current of (A3-A2) the
low band amplifier board (idling
current=1.8 amps and operating
current=12-13 amps, black
picture)
Reads the current of (A3-A3)
the low band amplif ier board
(idling current=1.8 amps and
operating current=12-13 amps,
black picture)
Reads the current of (A2-A1) the
low band amplifier board (idling
current=3 amps and operating
current=3 amps, black picture )

Display

Display

334B, Rev. 0 2-7

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

Table 2-7. VHF Amplifier Tray Fault Indicators

INDICATOR DESCRIPTION

DS1

Overdrive

DS2

Enable

DS3

Module Status

DS4

VSWR Cutback

DS5

Overtemperature

Table 2-8. VHF Amplifier Tray Control Adjustments

ADJUSTMENT DESCRIPTION

R2 – A7

Phase

R3 – A6

Gain

SAMPLE DESCRIPTION

J5

RF Front Panel Sample

2.3 Maintenance

The 334B is designed with components
that require little or no periodic
maintenance except for the routine
cleaning of the fans and the openings in
front panels of the trays.

The amount of time between cleanings
depends on the conditions within the
transmitter room. While the electronics
have been designed to function even if
covered with dust, a heavy buildup of
dust, dirt, or insects will affect the
cooling of the components. This could
lead to a thermal shutdown or premature
failure of the affected trays.

When the front panels of the trays
become dust covered, the top covers

Indicates that the level of drive is too high. The protection
circuit will limit the drive level to the set threshold. The fault
is generated on the overdrive protection board.
Indicates that the Enable supplied by the exciter tray is
present
Indicates that the forward power sample level is lower than

the set reference level
Indicates that the reflected level of the tray has increased
above 20%; this will automatically cut back the output power
of the tray. The fault is generated on the AGC control board.
Indicates that the temperature of (A4-A5, A4-A6 or A5-A2)
one of the thermal switches is above 175° F. When this fault
occurs, the Enable to the switching power supply is
immediately removed.

Adjusts the phase of the RF output by approximately 70°.

Adjusts the gain of the RF output when the amplifier control

board is in the AGC mode.

Table 2-9. VHF Amplifier Tray Sample

Forward power sample of the tray from the AGC control

board.

should be removed and any accumulated
foreign material should be removed. A
vacuum cleaner, utilizing a small wand­type attachment, is an excellent way to
suction out the dirt. Alcohol and other
cleaning agents should not be used
unless you are certain that the solvents
will not damage components or the silk­screened markings on the trays and
boards. Water-based cleaners can be
used, but do not saturate the
components. The fans and heatsinks
should be cleaned of all dust or dirt to
permit the free flow of air for cooling
purposes.

It is recommended that the operating
parameters of the transmitter be
recorded from the meters on the trays at
least once a month. It is suggested that

334B, Rev. 0 2-8

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

this data be retained in a rugged folder
or envelope. A sample format for a log
sheet is provided in Appendix B.
Photocopies of the log sheet should be
made to allow you to make continued
data entries.

2.4 Input Connections

The baseband audio input connects to
(A12) the A/V input and remote interface
assembly. The baseband audio connects
to TB1 for balanced audio or to jack J6
for composite, stereo, audio. The
baseband video input connects to jack
J2. NOTE: If another transmitter is
using the same composite audio and
video inputs, the loop through
connections on the rear of the VHF
exciter can be used. The video can be
connected to J2 and the composite audio
to J13.

NOTE: If your transmitter contains a
precise frequency kit, a 5/10 MHz
reference input must be connected to the
BNC jack J19 on the remote interface
assembly.

NOTE: If your transmitter contains a
receiver tray the RF input connects to the
“N” connector J1 or the “F” connector J18
on the remote interface assembly.

If the (A12) A/V input and remote
interface panel is not present in your

system, the baseband video and audio
inputs connect directly to the rear of the
VHF exciter.

NOTE: If your transmitter does not
contain the 4.5 MHz composite input kit,
the following description does not pertain
to your transmitter. The baseband video
input or the 4.5-MHz composite input
connects to jacks J1 or J2, which are
loop-through connected. The baseband
audio input connects to TB1 for balanced
audio or to jacks J3 or J13, which are
loop-thru connected, for composite,
stereo, audio. To use the (Optional) 4.5­MHz composite input kit, the baseband
audio can remain connected to the VHF
exciter even if the 4.5-MHz composite
input kit is used, but the baseband video
must be removed from J1 or J2 and the

4.5-MHz composite input must be
connected to J1 or J2. The baseband
select command must be removed from
J7-6 and J7-7.

2.5 Remote Connections

The remote connections listed in Table 2­10 are made to the (A12) A/V input and
remote interface assembly. The remote
connections are made to the 37 pos “D”
connector J9 or the 25 pos “D” connector
J10 on the assembly. Refer to the
interconnect drawing (1304391) to
confirm the remote pin connections.

334B, Rev. 0 2-9

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

Table 2-10. 334B Remote Interface Connections to (A12) the A/V Input

and Remote Interface Assembly

FUNCTION

Transmitter Enable Interlock J9-21

REMOTE JACK/PIN

NUMBER

INTERFACE TYPE

J9-21 and J9-22 must be
connected together for
normal operation. The

Transmitter Enable Interlock Rtn. J9-22

(1176-1038) jumper jack or
an external interlock can be
used.

Remote Control Commands

Transmitter Standby (Disable) J9-9 Contact closure
Transmitter Standby/Operate Rtn. J9-10
Transmitter Operate (Enable) J9-11 Contact closure

Transmitter Manual J9-15 Contact closure
Transmitter Auto/Manual Rtn. J9-16
Transmitter Auto J9-17 Contact closure

Power Level Raise (Optional) J9-27 Contact closure
Pwr Lvl Raise/Lower Rtn (Optional)

J9-28

Power Level Lower (Optional) J9-29 Contact closure

Modulator Select (Optional) J9-31 Contact closure
Modulator Select Rtn (Optional) J9-32

Remote Status Indications

Transmitter Operate (Enable) Ind. J9-12 50 mA max current sink
Operate/Standby Ind. Return J9-13
Transmitter Standby (Disable) Ind. J9-14 50 mA max current sink

Transmitter Aut o Indicator J9-18 50 mA max current sink
Auto/Manual Indicator Return J9-19
Transmitter Manual Indicator J9-20 50 mA max current sink

VSWR Cutback Indicator J9-23 50 mA max current sink
VSWR Cutback Indicator Return J9-24

Video Loss (Fault) Indicator J9-25 50 mA max current sink
Video Loss (Fault) Ind. Rtn. J9-26

Receiver Fault (Optional) J9-30

334B, Rev. 0 2-10

2000-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections

FUNCTION

Visual Output Power J9-1
Visual Output Power Rtn J9-2

Aural Output Power J9-3
Aural Output Power Rtn J9-4

Reflected Power J9-5
Reflected Power Rtn J9-6

Exciter Output Power J9-7
Exciter Output Power Rtn J9-8

Forward Output Power (A6) VHF
Amp #1
Forward Output Power (A6) Rtn J10-2

Reflected O/P Power (A6) VHF
Amp #1
Reflected O/P Power (A6) Rtn J10-4

Forward Output Power (A7) VHF
Amp #2
Forward Output Power (A7) Rtn J10-7

Reflected O/P Power (A7) VHF
Amp #2
Reflected O/P Power (A7) Rtn J10-9

Forward Output Power (A11) VHF
Amp #3
Forward Output Power (A11 Rtn J10-11

Reflected O/P Power (A11 VHF
Amp #3
Reflected O/P Power (A11) Rtn J10-13

NOTE: If your transmitter does not
contain the (A12) A/V input and remote
interface assembly, the remote
connections are made directly to the rear
of the VHF exciter at J10 a 25 pos “D”
connector or J11 a 37 pos “D” connector
and to each of the VHF amplifier trays at
J3 a 25 pos “D” connector. Refer to the

REMOTE JACK/PIN

NUMBER

Remote Metering

J10-1

J10-3

J10-6

J10-8

J10-10

J10-12

interconnect drawing (1304391) to
confirm the remote pin connections.

This concludes this chapter on the
System Description, Maintenance and
Remote Control Connections.

INTERFACE TYPE

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

1V full scale at 1kΩ source
resistance

334B, Rev. 0 2-11

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

Chapter 3

Installation and Setup Procedures

There are special considerations that
need to be taken into account before the
334B can be installed. For example, if
the installation is completed during cool
weather, a heat -related problem may not
surface for many months, suddenly
appearing during the heat of summer.
This section provides planning
information for the installation and set up
of the transmitter.

3.1 Site Considerations

The transmitter requires an AC input line
of 220 VAC with a rating of 25 amps that
connects to the transmitter cabinet.
Make sure that the proposed site for the
transmitter has the necessary voltage
requirements.

The 334B is designed and built to provide
long life with a minimum of maintenance.
The environment in which it is placed is
important and certain precautions must
be taken. The three greatest dangers to
the transmitter are heat, dirt, and
moisture. Heat is usually the greatest
problem, followed by dirt, and then
moisture. Over-temperature can cause
heat-related pro blems such as thermal
runaway and component failure. Each
amplifier tray in the transmitter contains
a thermal interlock protection circuit that
will shut down that tray until the
temperature drops to an acceptable level.

A suitable environment for the
transmitter can enhance the overall
performance and reliability of the
transmitter and maximize revenues by
minimizing down time. A properly
designed facility will have an adequate
supply of cool, clean air, free of airborne
particulates of any kind, and no
excessive humidity. An ideal
environment will require temperature in
the range of 40° F to 70° F throughout
the year, reasonably low humidity, and a
dust-free room. It should be noted that

this is rarely if ever attainable in the real
world. However, the closer the
environment is to this design, the greater
the operating capacity of the transmitter.

The fans, designed and built into the
transmitter, will remove the heat from
within the trays, but additional means
are required for removing this heat from
the building. To achieve this, a few
issues need to be resolved. The first step
is to determine the amount of heat to be
removed from the transmitter room.
There are generally three sources of heat
that must be considered. The first and
most obvious is the heat from the
transmitter itself. This can be
determined by subtracting the average
power to the antenna (1400 watts) from
the AC input power (4800 watts) . This
number in watts (3400) is then multiplied
by 3.41, which gives 11,594, the BTUs to
be removed every hour. 12,000 BTUs
per hour equals one ton, so a 1-ton air
conditioner will cool a 2000-watt
transmitter.

The second source of heat is other
equipment in the same room. This
number is calculated in the same way as
the equation for BTUs. T he third source
of heat is equally obvious but not as
simple to calculate. This is the heat
coming through the walls, roof, and
windows on a hot summer day. Unless
the underside is exposed, the floor is
usually not a problem. Determining this
number is usually best left up to a
qualified HVAC technician. There are far
too many variables to even estimate this
number without reviewing the detailed
drawings of the site that show all of the
construction details. The sum of these
three sources is the bulk of the heat that
must be removed. There may be other
sources of heat, such as personnel, and
all should be taken into account.

334B, Rev. 0 3-1

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

Now that the amount of heat that must
be removed is known, the next step is to
determine how to accomplish this. The
options are air conditioning, ventilation,
or a combination of the two. Air
conditioning is always the preferred
method and is the only way to create
anything close to an ideal environment.

Ventilation will work quite well if the
ambient air temperature is below 100° F,
or about 38° C, and the humidity is kept
at a reasonable level. In addition, the air
stream must be adequately filtered to
ensure that no airborne particulates of
any kind will be carried into the
transmitter. The combination of air
conditioning for summer and ventilation
during the cooler months is acceptable,
when the proper cooling cannot be
obtained through the use of ventilation
alone and using air conditioning
throughout the year is not feasible.

Caution: The use of air conditioning
and ven tilation simultaneously is not
recommended. This can cause
condensation in transmitters.

The following precautions should be
observed regarding air conditioning
systems:

1. Air conditioners have an ARI
nominal cooling capacity rating.
In selecting an air conditioner, do
not assume that this number can
be equated to the requirements of
the site. Make certain that the
contractor uses the actual
conditions that are to be
maintained at the site in
determining the size of the air
conditioning unit. With the
desired conditioned room
temperature under 80° F, the unit
must be derated, possibly by a
substantial amount.

2. Do not have the air conditioner
blowing directly onto the
transmitter. Condensation may
occur on, or worse in, the

transmitter under certain
conditions.

3. Do not isolate the front of the
transmitter from the back with the
thought of air conditioning only
the front of the unit. Cooling air is
drawn in at the front of all
transmitters and in the front and
back of others. Any attempt to
isolate the front from the rear will
adversely affect the flow of cooling
air.

4. Interlocking the transmitter with
the air conditioner is
recommended to keep the
transmitter from operating without
the necessary cooling.

5. The periodic cleaning of all filters
is a must.

When using ventilation alone, the
following general statements apply:

1. The blower, with attendant filters,
should be on the inlet, thereby
pressurizing the room and
preventing dirt from entering the
transmitter.

2. The inlet and outlet vents should
be on the same side of the
building, preferably the leeward
side. As a result, the pressure
differential created by wind will be
minimized. Only the outlet vent
may be released through the roof.

3. The inlet and outlet vents should
be screened with 1/8-inch
hardware cloth (preferred) or
galvanized hardware cloth
(acceptable).

4. Cooling air should enter the room
as low as practical but in no case
higher than four feet above the
floor. The inlet must be located
where dirt, leaves, snow, etc., will
not be carried in wit h the cooling
air.

334B, Rev. 0 3-2

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

5. The exhaust should be located as
high as possible. Some ducting is
usually required to insure the
complete flushing of heated air
with no stagnant areas.

6. The area of the filter, located in
the ducting, must be large enough
to insure a maximum air velocity
of 300 feet per minute through the
filter. This is not a conservative
number but a never-exceed
number. In a dusty or remote
location, this number should be
reduced to 150 CFM.

7. The inlet and outlet(s) must have
automatic dampers that close any
time the ventilation blower is off.

8. In those cases in which
transmitters are regularly off for a
portion of each day, a
temperature-differential sensor
that controls a small heater must
be installed. This sensor will
monitor inside and outside
temperatures simultaneously. If
the inside temperature falls to
within 5° F of the outside
temperature, the heater will come
on. This will prevent condensation
when the ventilation blower comes
on and should be used even in the
summer.

9. A controlled-air bypass system
must be installed to prevent the
temperature in the room from
falling below 40° F during
transmitter operation.

10. The blower should have two
speeds, which are thermostatically
controlled, and also be interlocked
with the transmitter.

11. The blower on high speed must be
capable of moving the required
volume of air into a half inch of
water pressure at the required
elevation. The free air delivery
method must not be used.

12. Regular maintenance of the filters,
if used, can not be
overemphasized.

13. It is recommended that a site plan
be submitted to Axcera for
comments before installation
begins.

In calculating the blower requirements,
filter size, and exhaust size, if the total
load is known in watts, 2000 CFM into ½
inch of water will be required for each
5000 watts. If the load is known in
BTUs, 2000 CFM into ½ inch of water will
be required for each 17,000 BTUs. The
inlet filter must be a minimum of seven
square feet, larger for dusty and remote
locations, for each 5000 watts or 17,000
BTUs. The exhaust must be at least four
square feet at the exhaust screen for
each 5000 watts or 17,000 BTUs.

The information presented in this section
is intended to serve only as a general
guide and may need to be modified for
unusually severe conditions. A
c ombination of air conditioning and
ventilation should not be difficult to
design (see Figure 3-1). System
interlocking and thermostat settings
should be reviewed with Axcera.

As with any equipment installation, it is
always good practice to consult the
manufacturer when questions arise. The
field support department at Axcera can
be contacted at [phone].

334B, Rev. 0 3-3

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

Figure 3-1. 1 kW Minimum Ventilation Configuration

3.2 Unpacking the Cabinet and Trays

Note: Air conditioning and any
related heat exhau st ducts should be
in place before continuing with the
installation of the transmitter.

Thoroughly inspect the cabinet and all
other materials upon their arrival.
Axcera certifies that upon leaving our
facility the equipment was undamaged
and in proper working order. The
shipping containers should be inspected
for obvious damage that indicates rough
handling. Check for dents and scratches
or broken switches, meters, or
connectors. Any claims against in-transit
damage should be directed to the carrier.
Inform Axcera as to the extent of any
damage as soon as possible.

Remove the cabinet and the trays from
the crates and boxes. Remove the straps
that hold the cabinet to the shipping skid
and slide the cabinet from the skid.
Remove the plastic wrap and foam
protection from around the cabinet. Do
not remove any labeling or tags from any
cables or connectors; these are
identification markers that make
assembly of the transmitter much easier.

Remove the two L-brackets, mounted on
the front panel rails, which held the trays
in place during shipment. The trays are
mounted in the cabinet using Chassis
Trak cabinet slides as shown in Figure
3-2. The tray slides are on the sides of
the three VHF amplifier trays and the
VHF exciter tray. Inspect the trays for
any loose hardware or connectors,
tightening as needed.

334B, Rev. 0 3-4

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

Figure 3-2. Chassis Trak Cabinet Slides

Open the rear door and inspect the
interior of the cabinet for packing
materials and carefully remove any that
are found. Slowly slide each tray in and
out to verify that they do not rub against
each other and have no restrictions to
free movement. It may be necessary to
adjust the position of the trays to keep
them from rubbing. This is accomplished
by loosening the cabinet slide mounting
bolts that hold the front of the slide to
the mounting frame of the cabinet and
moving the tray up or down, as needed,
to correct for the rubbing.

3.3 Installing the Cabinet and Trays

The air intake to the 2000-watt
transmitter is only intended for room air.
The cabinet should be positioned for
adequate air intake and exhaust, the
opening of the rear door, if present;
access to the trays, including sliding
them out for testing, the main AC
hookup, and the installation of the output
transmission line. The cabinet should be
grounded using copper strapping
material and should be permanently
mounted to the floor of the site using the
holes in the bottom of the cabinet.

Once the cabinet is in place, and the
trays are checked for damage, the main
AC hookup can be made.

Caution: Before connecting the 220
VAC, make certain that the circuit
breaker associated with the
transmitter has been switched off.

The main AC input circuit to the 2000­watt transmitter should be a 25-amp,
220-VAC line, using AWG 10 wire, inside
of a 1-1/4-inch conduit. The three wire
220 VAC input is connected to the AC
distribution block, white to white, black
to black and green to green by stripping
the ends of the wires, approximately ½”,
and placing them into the proper hole
and tightening the retaining screws that
holds them in place. NOTE: The 220VAC
should be connected by a qualified
electrician.

The AC is distributed to the trays through
AC plugs that connect from the power
distribution block to the rear of each tray.

The output of the (A16) coupler assembly
at (A16-J2), which is a 1-5/8” connector
and the RF output for the transmitter,
should connect to the transmission line
for the antenna system.

334B, Rev. 0 3-5

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

This completes the unpacking and
installation of the 334B 2000-watt VHF
television transmit ter. Refer to the setup
and operation procedures that follow
before applying power to the transmitter.

3.4 Setup and Operation Procedures

Initially, the transmitter should be turned
on with the RF output at (A16-J2) of the
coupler assembly terminated into a
dummy load of at least 2000 watts. If a
load is not available, check that the
output of the coupler assembly is
connected to the antenna.

The baseband audio and video inputs and
any remote control connections must be
made to the (A12) A/V input and remote
interface assembly. The baseband
balanced audio input connects to the
terminal block TB1 or the composite
audio input connects to the BNC jack J6.
Connect the baseband video input to the
BNC jack J2.

NOTE: If your transmitter does not
contain the 4.5 MHz composite input kit,
the following description does not pertain
to your transmitter. The baseband audio
input can remain connected when the

4.5-MHz composite input is in use
without affecting the operation of the
tray. Connect the baseband video input
to BNC jack J2 on the A/V input and the
remote interface assembly. If the
(optional) 4.5-MHz composite input kit is
purchased, connect the 4.5-MHz
composite input to the BNC jack J2. To
use the 4.5-MHz composite input, the

4.5-MHz composite input must be
connected to J2 and the baseband select
must be removed from J7-6 and J7-7 on
the rear of the VHF exciter tray. To use
the baseband video and audio inputs, the
baseband video input must be connected
to J2, the baseband audio must be
connected to the proper jack, and the
baseband select must be connected from
J7-6 and J7-7 on the rear of the VHF
exciter tray.

If the (A12) A/V input and remote
interface assembly is not present in the
system, connections are made directly to
the rear of the VHF exciter tray.
Connect the baseband balanced audio
input to the terminal block TB1 or the
composite audio input to the BNC jack J3
or J13 on the rear of the VHF exciter.
The baseband audio input can remain
connected when using the (Optional) 4.5 ­MHz composite input, if present, without
affecting the operation of the tray.
Connect the baseband video input to the
BNC jack J2 or J1 also on the rear of the
VHF exciter or, if the (optional) 4.5-MHz
composite input kit is purchased, connect
the 4.5-MHz composite input to the BNC
jack J2 or J1. To use the 4.5-MHz
composite input, the 4.5-MHz composite
input must be connected to J2 or J1 and
the baseband select must be removed
from J7-6 and J7-7 on the rear of the
tray. To use the baseband video and
audio inputs, the baseband video input
must be connected to J2 or J1, the
baseband audio must be connected to
the proper jack, and a baseband select
must be connected from J7-6 and J7-7.

Switch on the main AC for the
transmitter and the circuit breakers
located on the re ar of the VHF exciter,
and on the front of the three VHF
amplifier trays. On the VHF exciter tray,
switch the Operate/Standby switch to
Standby and the Auto/Manual switch to
Manual. Normal operation of the
transmitter is in Automatic, which uses
the video input to the VHF exciter as an
Operate/Standby switch. In Auto, if the
input video is lost for approximately 7
seconds, the transmitter will
automatically revert to Standby and,
when the video signal is restored, the
transmitter will quickly return to Operate.

Move the Operate/Standby switch on the
VHF exciter tray to Operate. This will
apply enables to the switching power
supplies in each of the VHF amplifier
trays. Observe that a power supply
voltage reading of +28 V is on the front

334B, Rev. 0 3-6

2000-Watt VHF Low Band Transmitter Chapter 3, Installation and Setup Procedures

panels of the VHF amplifier trays, in the
power supply position.

NOTE: If the transmitter does not switch
to Operate when the Operate/Standby
switch is placed in Operate, check that on
the (A12) A/V input and remote interface
assembly an external interlock plug is
connected to J9, with a jumper wired
from pins 21 to 22. If the (A12) A/V
input and remote interface assembly is
not present in your transmitter, check
that an external interlock plug is
connected to J11, with a jumper wired
from pins 23 to 24, on the rear of the
VHF exciter.

With the transmitter in Operate, monitor
the front panel meter of the VHF exciter
tray. In the % Visual Power position, it
should read 100%. If necessary, adjust
the screwdriver adjust power pot on the
front panel of the VHF exciter for 100%.
Check the % Reflected Power position. If
the % Reflected Power is very high,
above 10%, a problem exists with the
output coaxial lines and they will need to
be checked. A center bullet missing from
the coax lines or loose bolts on the
connections can cause this problem.

The gain and phase controls on the front
panels of the individual VHF amplifier
trays were adjusted at the factory to
obtain an output of 100% for the
transmitter and should not need to be
readjusted. The front panel readings on
the individual VHF amplifier trays may

not be the same. Refer to the Test Data
Sheet for the transmitter to compare the
final readings from the factory with the
readings on each of the trays after the
setup. If a reading is off by a significant
amount, refer to the phasing and power
adjustment procedures for the VHF
amplifier trays in Chapter 5, Detailed
Alignment Procedures, of this manual
before trying to make any adjustments.

If a dummy load is connected to the
transmitter, switch the unit to Standby
and switch off the main AC circuit
breaker. Remove the dummy load and
make all of the connections that are
needed to connect the transmitter to the
antenna. Switch the main AC circuit
breaker on and the Operate/Standby
switch to Operate. Adjust the output
power screwdriver pot to achieve an
output of 100%.

If the transmitter is already connected to
the antenna, check that the output is
100%. If necessary, adjust the power
screwdriver pot.

This completes the transmitter setup and
operation procedure s for the 334B VHF
low band transmitter. The transmitter
can now be operated normally.

If a problem occurred during the setup
and operation procedures, refer to
Chapter 5, Detailed Alignment
Procedures, of this manual for more
information.

334B, Rev. 0 3-7