Daniels VT-3H035-SWA3 User manual

DANIELS
ELECTRONICS LTD.
TM
MT-3 RADIO SYSTEMS
VHF ENHANCED
TRANSMITTER
INSTRUCTION
MANUAL
Covers model: VT-3H035-SWA3, VT-3H045-SWA3
Copyright ©1998 Daniels Electronics Ltd. All rights reserved. No part of this publication may
be reproduced, stored in a retrieval system or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording or otherwise, without the prior written consent
of Daniels Electronics Ltd.
DE™ is a registered trademark of Daniels Electronics Ltd. registered in the United States Patent
and Trademark Office.
Issue: 1 Rev A Previous Issue: 1
Issue Date: September 98 Previous Issue Date: July 97 Daniels Electronics Ltd.
Printing Date: Month Year Victoria, B.C.
Part No.: IM20-VT3H040 PRINTED IN CANADA

DEDANIELS
ELECTRONICS
ii VT-3H040 VHF Enhanced Transmitter Instruction Manual
Document Control:
This document has been produced, verified and controlled in accordance with
Daniels Electronics’ Quality Management System requirements.
Please report any errors or problems to Daniels Electronics’ Customer Service
Department
NOTE:
The user's authority to operate this equipment could be revoked through any
changes or modifications not expressly approved by Daniels Electronics Ltd.
The design of this equipment is subject to change due to continuous
development. This equipment may incorporate minor changes in detail from
the information contained in this manual.

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual iii
TABLE OF CONTENTS
Page
1 GENERAL
1.1 Introduction.................................................................................................... 1-1
1.2 Manual Organization ..................................................................................... 1-1
1.3 VT-3H040 Transmitter Family Models......................................................... 1-2
1.4 Performance Specifications ........................................................................... 1-3
1.4.1 General............................................................................................... 1-3
1.4.2 Audio Specifications.......................................................................... 1-5
1.4.3 Physical Specifications ...................................................................... 1-6
2 SYSTEM OVERVIEW
2.1 Transmitter Operation.................................................................................... 2-1
2.2 Frequency Selection....................................................................................... 2-2
2.3 Transmitter Assembly and Adjustment ......................................................... 2-2
2.3.1 Complete Transmitter Alignment ...................................................... 2-3
2.3.2 Frequency Change ............................................................................. 2-3
2.3.3 Output Power Adjustment.................................................................. 2-4
2.3.4 Deviation Setting ............................................................................... 2-5
2.3.5 Setting RF Alarm Thresholds ............................................................ 2-5
2.4 Recommended Test Equipment List.............................................................. 2-5
2.5 Repair Note .................................................................................................... 2-6
2.6 Printed Circuitboard Numbering Convention................................................ 2-6
3 ILLUSTRATIONS
3.1 MT-3 Transmitter Front Panel....................................................................... 3-1
3.2 MT-3 Transmitter Case - Exploded View ..................................................... 3-2
4 PARTS LISTS ........................................................................................................... 4-1
5 REVISION HISTORY............................................................................................... 5-1
MODULE MANUALS
Transmitter Main Board Instruction Manual ....................................IM20-MT3TXMN
VT3H040 VHF Amplifier Instruction Manual .............................. IM20-VT3040AMP
OS-3A/H Enhanced Synthsizer Instruction Manual 29-470 MHz ......... IM10-OS3AH
VT-3H040 Channel Designation Table .......................................... IM20-VT3H040CT

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual 1
1 GENERAL
1.1 Introduction
The VT-3H040 transmitter is a low power, synthesized FM transmitter capable of operating in
20 kHz or 25 kHz channels and within one of two bands: 29 MHz to 38 MHz or 38 MHz to 50
MHz. The transmitter is rated for continuous duty at an RF output power of 3.0 Watt. The RF
output power level is preset at the factory. A modular design allows each of the transmitter's
modules; MT-3 Transmitter Main Board, MT-3 Audio Processor, VT-3H040 Amplifier and OS-
3H040 Synthesizer to be individually assembled and tested. This facilitates construction, tuning,
maintainance as well as troubleshooting procedures. The synthesizer module can be programmed
to have up to 16 channels exclusive to one frequency band.
The VT-3H040 Transmitter is designed to interface with Daniels Electronics' MT-3 Repeater
System while maintaining MT-2 System compatibility. Both radio systems are characterized by
dependable, low maintanence performance under the most severe environmental conditions.
1.2 Manual Organization
The organization of this manual reflects the modular makeup of the VT-3 product line. Each
module is fully described within its respective submanual, all of which are contained within this
document. In general, each submanual contains:
1. A functional description and specification summary,
2. a detailed technical description (Theory of Operation) and
3. assembly, setup and alignment procedures relevent to that particular module.
The module manuals are as follows.
Note: material presented in a given "sub-manual" may include information related to other
module versions not directly appllicable to the VT-3H040 Transmitter family (eg, the OS-3H
Synthesizer Instruction Manual covers models from 29 MHz to 512 MHz).
Transmitter Manual: This manual provides an overview of the complete transmitter, manual
organization and assembly in terms of the other modules.
MT-3 Transmitter Main Board: This manual pertains to the audio processor module, transmitter
Main Board and Front Panel Board. Most of the user selectable options are accessed within the
Transmitter Main Board module, including channel selection. Since all external connections
(including power and signal lines) are made to the Transmitter Main Board, most of the material
pertaining to transmitter operation and installation is found here.

DEDANIELS
ELECTRONICS
2 VT-3H040 VHF Enhanced Transmitter Instruction Manual
VT-3H040 VHF Amplifier: The amplifier module provides the final stages of RF power
amplification and harmonic filtering for the transmitter. This manual is intended primarily as a
reference since the amplifier module is adjusted at the factory.
OS-3H040 Synthesizer: This manual pertains to the synthesizer module. Channel selection is
described in the 'Transmitter Main Board' Manual.
VT-3H040 Channel Designation Table: This document relates operating frequency to the
transmitter channel number (see section 2.1).
1.3 VT-3H040 Transmitter Family Models
The VT-3H040 line of transmitters has a single RF power output rating of 3.0 Watt, with wide
band FM (20 kHz or 25 kHz channels) and employs synthesizer based frequency generation. The
two basic (i.e. no options added) band specific models of the transmitter are as follows:
VT-3H035-SWA3: 29 MHz to 38 MHz
VT-3H045-SWA3 38 MHz to 50 MHz
The frequency is determined by the model of synthesizer and by the lowpass filter that is
installed in the amplifier module (see the VT-3H040 VHF Amplifier manual for details). A
group of channels spanning 38 MHz can be accomodated by one of the models providing that the
frequency span does not exceed 1.0 MHz. Model VT-3H035-SWA3 can operate at frequencies
up to 38.5 MHz and is the preferred choice when spanning 38 MHz. Consult the factory for
futher information regarding operation around this frequency.

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual 3
1.4 Performance Specifications
1.4.1 General
The following is a general set of specifications for the generic VT-3H040 transmitter. Additional
specifications, specific to individual modules may be found in their respective submanuals.
Type: MT-3 Series Transmitter
Family: VT-3H040
Compatibility: MT-2 Series and MT-3 Series Radio Systems
Frequency Range: 29.0 MHz to 50.0 MHz
RF Power Output: 3.0 Watt Fixed (± 1.5 dB with temperature and
supply voltage).
System Impedance: 50 Ω; Type N connector.
Duty Cycle: 100%: Continuous operation from -30˚C to +60˚C
(optional -40˚C to +60˚C).
Harmonic Emissions: More than 90 dB below carrier.
Spurious Emissions: More than 80 dB below carrier.
Transmitter Mismatch Protection: 20:1 VSWR at all phase angles.
Transmitter Alarm: Forward power sense and reverse VSWR;
- open collector output (separate or 'OR'ed);
- linear output (separate lines only).
Modulation: 16K0F3E
Synthesizer Reference Frequency: 9.600000 MHz or 10.000000 MHz ; selectable.
Channel Spacing: 20 / 25 kHz
Frequency Stability: Standard: ±1 ppm, -30˚C to +60˚C,
optional -40˚C to +60˚C
Channel Selection: In 5 kHz or 6.25 kHz increments selected through
four internal BCD rotary switches. Preset capability
for 16 channel memory selectable through external
control.

DEDANIELS
ELECTRONICS
4 VT-3H040 VHF Enhanced Transmitter Instruction Manual
Standby Current and rise time: 95 % RF power, 95 % system deviation within;
(See also 'Transmitter Main • 10 ms: typ. 185 mA (Mode 4);
Board Instruction Manual) • 25 ms: typ. 160 mA (Mode 2);
• 50 ms: typ. 15 mA (Mode 1);
• Mode 3 not used in Synthesized Transmitters.
DOC Type Approval RSS119 Issue 6
FCC Type Acceptance: Parts 22, 90 FCC ID: H4JVT-3H040-S
Operating Temperature Range: -30˚C to +60˚C, optional -40˚C temperature test.
Operating Humidity: 95% RH (non-condensing) at +25˚C.
Operating Voltage: +13.8 Vdc Nominal (range +11 to +16 Vdc),
+9.5 Vdc Regulated.
Total Transmit Current: 0.8 Amp typical; 1.2 Amp maximum
Front Panel Controls: NORM (repeat mode), OFF, and KEY TX (Tx on).
PTT Activation: Active to ground with or without time-out timer.
Microphone activated with or without time-out
timer.
Front Panel switch: KEY TX - without time-out
timer; NORM - with or without time-out-timer;
Isolated (optional relay) with or without time-out
timer.
PTT Time Out Timer: Selectable from 1 sec. to 8 hrs. (factory set 5 min.).

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual 5
1.4.2 Audio Specifications
Audio Input: Balanced 600 ohm or unbalanced (optional).
Input level sensitivity, -25 dBm to 0 dBm.
Audio Response: Pre-emphasis (6 dB per octave); +1.0 to -2.0 dB
from 300 Hz to 3 kHz;
Flat Audio Response: +1 to -1 dB from 100 Hz to 3 kHz.
Audio Deviation: Preset to ±3.0 kHz with a 1 kHz tone.
Subtone Audio Input 1: 0.5 Vpp at 200 Hz for ±500 Hz deviation
(internally adjustable).
Subtone Audio Input 1 Frequency range: 60 Hz to 300 Hz.
Subtone Audio Input 2: 0.5 Vpp at 100 Hz for ±500 Hz deviation
(internally adjustable).
Subtone Audio Input 2 Frequency range: DC to 150 Hz.
Direct Modulation Input: 0.5 Vrms at 1 kHz or ±3 kHz deviation.
Direct Modulation Frequency range: DC to 5 kHz.
Audio Distortion: Less than 2.5% THD; 1 kHz tone at 1.5 kHz or
3 kHz deviation (-40°C to +60°C).
Hum and Noise: Better than 55 dB
(test receiver band limited: 400 Hz to 30 kHz).

DEDANIELS
ELECTRONICS
6 VT-3H040 VHF Enhanced Transmitter Instruction Manual
1.4.3 Physical Specifications
Physical Dimensions: Width: Height: Depth:
7.1 cm (2.8 in) 12.8 cm (5.05 in) 19 cm (7.5 in)
Module Weight: 1.5 kg (3.3 lbs)
Corrosion Prevention: Anodized aluminum construction. Stainless steel
hardware. Selectively conformal coated glass epoxy
2 and 4 layer printed circuitboards. Gold plated
module connectors.
Module Design: Compact Eurostandard modular design. Plug-in
modules mate with Daniels standard M3 repeater
subrack. Subracks / modules comply with IEEE
1101, DIN 41494 and IEC 297-3 (mechanical size /
modular arrangement).
External Connections: RF Connection: type N connector located on the
transmitter module front panel. Motherboard
Connections (Audio, Power, and Control) are made
through a 48 pin, gold plated, type F connector on
the rear of the transmitter module. User connection
made through mated "mother board" assembly of
the repeater subrack. Type F standard connector
complies with DIN 41612 Level 2 (200 mating
cycles, 4 day 10 ppm SO2gas test with no
functional impairment and no change in contact
resistance).
Handle Text Colour: Orange.

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual 3-1
3 ILLUSTRATIONS
3.1 MT-3 Transmitter Front Panel
VT3040M1
ON / OFF SWITCH
TYPE N RF
OUTPUT JACK
SMA REFERENCE
INPUT JACK
TRANSMIT INDICATOR LED
TRANSMITTER
MODEL IDENTIFIER
FACTORY SET
OPERATING
FREQUENCY
MICROPHONE
CONNECTOR
TRANSMITTER
TX
REFERENCE
INPUT
DANIELS
ELECTRONICS LTD.
OFF
NORM
KEY TX
MIC
RF OUT
FREQUENCY (MHz)
33.25000
MADE IN CANADA
VT-3H035-SWA3
MADE IN CANADA
MADE IN CANADA
ORANGE TEXT

DEDANIELS
ELECTRONICS
3-2 VT-3H040 VHF Enhanced Transmitter Instruction Manual
3.2 MT-3 Transmitter Case - Exploded View
3 FINGER GASKET (2)
A
A
A
A
B
B
B
B
MT3TXM2B

DEDANIELS
ELECTRONICS
VT-3H040 VHF Enhanced Transmitter Instruction Manual 5-1
5 REVISION HISTORY
ISSUE DATE DESCRIPTION AND (REASON)

DANIELS
ELECTRONICS LTD.
TM
MT-3 RADIO SYSTEMS
FM TRANSMITTER
MAIN BOARD
INSTRUCTION MANUAL
Covers: Main Board for
UT-3/xxx-xxxx UHF FM Transmitters and
VT-3/xxx-xxxx VHF FM Transmitters
With: Version 1.8 FM Audio Processor Board or
Version 2.3 FM Audio Processor Board
Copyright ©2003 Daniels Electronics Ltd. All rights reserved. No part of this publication may be reproduced, stored
in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or
otherwise, without the prior written consent of Daniels Electronics Ltd.
DE™ is a registered trademark of Daniels Electronic Ltd. registered in the U.S. Patent and Trademark Office.
Printing Date: Apr 2003 Daniels Electronics Ltd.
Issue Date: Apr 2003 Previous Issue Date: Nov 98 Victoria, BC
Issue: 4Previous Issue: 3
Part No.: IM20-MT3TXMN PRINTED IN CANADA

ii Transmitter Main Board Instruction Manual IM20-MT3TXMN
Reviewed By:
Quality Assurance:
CLAUDIA BOORMAN
_________________
Quality Manager Signature Date
NOTE:
The user's authority to operate this equipment could be revoked through any
changes or modifications not expressly approved by Daniels Electronics Ltd.
The design of this equipment is subject to change due to continuous
development. This equipment may incorporate minor changes in detail from the
information contained in this manual.

Transmitter Main Board Instruction Manual IM20-MT3TXMN iii
TABLE OF CONTENTS
1 GENERAL.......................................................................................................................1-1
1.1 Introduction............................................................................................................1-1
1.2 Performance Specifications....................................................................................1-1
1.2.1 General Specifications......................................................................................1-1
1.2.2 Audio Specifications........................................................................................1-2
2 THEORY OF OPERATION............................................................................................2-1
2.1 Transmitter Main Board.........................................................................................2-1
2.1.1 General Theory of Operation...........................................................................2-1
2.1.2 Transmitter Push-To-Talk................................................................................2-1
2.1.2.1 Microphone PTT.........................................................................................2-1
2.1.2.2 PTT With Time-Out-Timer..........................................................................2-2
2.1.2.3 PTT No Time-Out-Timer.............................................................................2-2
2.1.2.4 PTT Relay....................................................................................................2-2
2.1.2.5 PTT Output..................................................................................................2-3
2.1.2.6 PTT Voltage Switching................................................................................2-3
2.1.3 Transmitter Standby Modes.............................................................................2-4
2.1.3.1 Audio Circuits..............................................................................................2-6
2.1.3.2 Microphone Audio.......................................................................................2-6
2.1.3.3 Received Audio............................................................................................2-6
2.1.4 Channel Selection.............................................................................................2-6
2.1.4.1 Synthesized Transmitter...............................................................................2-6
2.1.4.2 Crystal Controlled Transmitter.....................................................................2-7
2.1.5 Amplifier Circuits.............................................................................................2-7
2.1.6 Time-Out-Timer Circuitry................................................................................2-8
2.1.6.1 Optional Time-Out Timer on the Audio Processor Board............................2-8
2.2 MT-3 Front Panel Board........................................................................................2-10
2.3 Version 1.8 Audio Processor.................................................................................2-11
2.3.1 General.............................................................................................................2-11
2.3.2 Power Requirements........................................................................................2-11
2.3.3 Audio Processor Turn-on Time........................................................................2-12
2.3.4 Audio Processor Signals..................................................................................2-12
2.3.4.1 Audio Processor Outputs.............................................................................2-12
2.3.4.2 Audio Processor Modulation Output...........................................................2-12
2.3.4.3 Audio Processor Low Frequency / Direct Mod. Output..............................2-13
2.3.4.4 Audio Processor Inputs...............................................................................2-13
2.3.4.5 Audio Processor Microphone Input.............................................................2-13
2.3.4.6 Audio Processor Balanced Input..................................................................2-13
2.3.4.7 Audio Processor Auxiliary Input.................................................................2-14
2.3.4.8 Audio Processor Subtone Inputs.................................................................2-14
2.3.4.9 Audio Processor Direct Modulation Input...................................................2-14

iv Transmitter Main Board Instruction Manual IM20-MT3TXMN
2.4 Version 2.3 Audio Processor.................................................................................2-15
2.4.1 Introduction......................................................................................................2-15
2.4.2 Version 2.3 FM Audio Processor Block Diagram...........................................2-17
2.4.3 Factory Configuration......................................................................................2-18
2.4.4 Turn-on Time...................................................................................................2-19
2.4.5 Low Frequency Modulation.............................................................................2-19
2.4.6 Audio Processor Signals..................................................................................2-20
2.4.6.1 FM Audio Processor Outputs......................................................................2-20
2.4.6.2 Audio Processor Modulation Outputs.........................................................2-20
2.4.6.3 Audio Processor Microphone Input.............................................................2-21
2.4.6.4 Audio Processor Balanced Input..................................................................2-21
2.4.6.5 Audio Processor Auxiliary Input.................................................................2-21
2.4.6.6 Audio Processor Subtone Inputs.................................................................2-22
2.4.6.7 Direct Modulation Input..............................................................................2-22
2.4.6.8 Low Frequency Modulation.........................................................................2-22
2.4.7 Audio Processor Signal Paths (Version 2.3)....................................................2-23
3 TRANSMITTER ALIGNMENT.....................................................................................3-1
3.1 General...................................................................................................................3-1
3.2 Repair Note............................................................................................................3-1
3.3 Printed Circuit Board Numbering Convention .......................................................3-1
3.4 Recommended Test Equipment List.......................................................................3-2
3.5 Standard Factory Settings and Jumper Configuration............................................3-2
3.5.1 MT-3 Transmitter Main Board Factory Configuration.....................................3-2
3.6 MT-3 Transmitter Main Board Configuration........................................................3-4
3.6.1 General.............................................................................................................3-4
3.6.2 MT-3 Transmitter Main Board Test Points......................................................3-4
3.7 Module Installation and Removal...........................................................................3-5
3.8 Audio Processor Alignment ...................................................................................3-6
3.8.1 Multiple Channel Transmitters.........................................................................3-7
3.8.2 Audio Processor Version Identification and Adjustment Locations..................3-7
3.8.3 Audio Processor Alignment Procedures...........................................................3-9
3.8.3.1 Transmitters with Pre-Emphasis and CTCSS Subtone................................3-9
3.8.3.2 Transmitters with Flat Audio and CTCSS subtone......................................3-13
4 TROUBLESHOOTING..................................................................................................4-1
4.1 Balanced Input Test................................................................................................4-1
4.2 Frequency Response Test......................................................................................4-1
4.3 Subtone Input Test.................................................................................................4-1
5 TEMPERATURE COMPENSATION............................................................................5-1
6 TRANSMITTER INTERCONNECT PIN DEFINITIONS............................................6-1
7 AUDIO PROCESSOR JUMPER CONFIGURATIONS...............................................7-1
7.1 Version 1.8 Audio Processor Jumper Configuration..............................................7-1
7.2 Version 2.3 Audio Processor Jumper and Select Value Tables ..............................7-3

Transmitter Main Board Instruction Manual IM20-MT3TXMN v
7.2.1 Wideband VHF and UHF Synthesized Transmitters.......................................7-3
7.2.2 Narrowband VHF and UHF Synthesized Transmitters....................................7-4
7.2.3 Wideband Crystal Transmitters........................................................................7-6
7.2.4 Narrowband Crystal Transmitters....................................................................7-7
7.2.5 LTRTM Configuration.......................................................................................7-8
8 ILLUSTRATIONS AND SCHEMATIC DIAGRAMS...................................................8-1
8.1 Transmitter Block Diagram....................................................................................8-1
8.2 Transmitter Main Board - Top Side Component Layout.......................................8-3
8.3 Transmitter Main Board - Bottom Side Component Layout...................................8-4
8.4 Transmitter Main Board - Schematic Diagram......................................................8-5
8.5 Front Panel Board - Component Layout...............................................................8-6
8.6 Front Panel Board - Schematic Diagram...............................................................8-7
8.7 Version 1.8 Audio Processor - Component Layout................................................8-8
8.8 Version 1.8 Audio Processor - Schematic Diagram ..............................................8-9
8.9 Version 2.3 Audio Processor - Component Layout................................................8-10
8.10 Version 2.3 Audio Processor - Schematic Diagram...............................................8-11
8.11 Optional Time Out Timer Assembly......................................................................8-12
9 PARTS LISTS..................................................................................................................9-1
9.1 Transmitter Main Board Parts List.........................................................................9-1
9.1.1 Transmitter Main Board Electrical Parts List....................................................9-1
9.1.2 Transmitter Main Board Mechanical Parts List................................................9-3
9.1.3 MT-3 Front Panel Board Electrical Parts List..................................................9-4
9.2 MT-3 Audio Processor Parts List (Version 1.8)....................................................9-5
9.3 FM Audio Processor Parts List (Version 2.3)........................................................9-8
10 REVISION HISTORY.....................................................................................................10-1

vi Transmitter Main Board Instruction Manual IM20-MT3TXMN
LIST OF FIGURES
LIST OF TABLES
Figure 1 Audio Processor Block Diagram........................................................................2-17
Figure 2 Interconnection Pin Layout Diagram..................................................................2-18
Figure 3 Microphone and Balanced Input Circuitry,V2.3 Audio Processor.....................2-23
Figure 4 Limiter and Splatter Filter, V2.3 Audio Processor...............................................2-24
Figure 5 Bypassing Compression,V2.3 Audio Processor................................................2-25
Figure 6 TX Audio Control Circuitry,V2.3 Audio Processor...........................................2-26
Table 1 Mode Condition Table..........................................................................................2-4
Table 2 Standby Mode Selection Table.............................................................................2-5
Table 3 FM Audio Processor Total Current Consumption................................................2-5
Table 4 Time-Out-Timer Settings......................................................................................2-9
Table 5 MT-3 Audio Processor Current Consumption...................................................2-11
Table 6 Bandwidth Table.................................................................................................2-15
Table 7 Factory Configuration........................................................................................2-18
Table 8 Turn on Time......................................................................................................2-19
Table 9 Transmitter Main Board Jumpers.........................................................................3-3
Table 10 Main Board Test Points........................................................................................3-4
Table 11 Waveform Levels..................................................................................................4-1
Table 12 Interconnection Pin Definitions ............................................................................6-1
Table 13 Audio Processor Version 1.8 Jumper Settings......................................................7-2
Table 14 Jumper and Select Values Table - Wideband Synthesized Transmitters ...............7-3
Table 15 Jumper and Select Values Table - Narrowband Synthesized Transmitters............7-4
Table 17 Jumper and Select Values Table - Wideband Crystal Transmitters.......................7-6
Table 18 Jumper and Select Values Table - Narrowband Crystal Transmitters....................7-7
Table 19 Jumper and Select Values Table - LTRTM Modulated Transmitters.......................7-8

Transmitter Main Board Instruction Manual IM20-MT3TXMN 1-1
1GENERAL
1.1 Introduction
The MT-3 Transmitter Main Board integrates the MT-3 Front Panel Board, MT-3 Audio
Processor, Synthesizer or Crystal Controlled Oscillator module, and Amplifier module together to
comprise a MT-3 series transmitter (see section 5.1: MT-3 Transmitter Block Diagram). The Front
Panel Board and the Audio Processor are soldered directly to the Transmitter Main Board while the
Amplifier and the Synthesizer or Crystal Controlled Oscillator module are frequency band
sensitive, plug-in modules. Circuitry and jumpers on the Transmitter Main Board control the
operation of the modules as well as the overall operation of the MT-3 transmitter. Power and signal
connections are made through the 48 pin type 'F' connector on the rear of the Transmitter Main
Board where they are then routed to the other MT-3 modules. The front and rear panels are
attached to the Transmitter Main Board and together with the extruded aluminum shell, form the
transmitter enclosure.
Note: LTRTM is a trademark of E.F. Johnson Co.
1.2 Performance Specifications
1.2.1 General Specifications
Type: MT-3 Series Transmitter
Compatibility: MT-3 Series Amplifier, OC-3 Crystal Controlled Oscillator
module, OS-3 and OS-3H Frequency Synthesizer modules.
Modulation: 11K0F3E or 16K0F3E (Frequency Modulation).
Operating Temperature Range: -30˚C to +60˚C, optional -40˚C to +60˚C temperature test.
Operating Humidity: 95% RH (non-condensing) at +25°C.
Operating Voltage: +9.5 VDC Regulated. +13.8 VDC Nominal (11 - 16 VDC).
Front Panel Controls: NORM (repeat mode), OFF, and KEY TX (TX on).

1-2 Transmitter Main Board Instruction Manual IM20-MT3TXMN
PTT Activation: • Active to ground with or without time-out-timer.
• Microphone activated with or without time-out-timer.
• Front Panel switch: KEY TX - without time-out-timer.
• NORM - with or without time-out-timer.
• Isolated (optional relay) with or without time-out-timer.
PTT Time-Out-Timer: Selectable from 1 sec. to 8 hrs. (Factory Default: 5 min.).
1.2.2 Audio Specifications
Audio Input: Balanced 600 ohm or unbalanced (optional).
Input level sensitivity, -25 dBm to 0 dBm.
Audio Response: Pre-emphasis (6 dB per octave); +1.0 to -1.0 dB
from 500 Hz to 2.5 kHz;
Flat Audio Response: +1 to -1 dB from 300 Hz to 2.5 kHz.
Audio Deviation: Preset to ±1.5 kHz (Narrow Band) or ±3.0 kHz (Wide Band)
with a 1 kHz tone (capable ±2.5 kHz or ±5.0 kHz).
Subtone Audio Input 1: 0.5 Vpp at 200 Hz for ±500 Hz deviation
(internally adjustable).
Subtone Audio Input 1 Frequency range: 60 Hz to 300 Hz.
Subtone Audio Input 2: 0.5 Vpp at 100 Hz for ±500 Hz deviation
(internally adjustable).
Subtone Audio Input 2 Frequency range: DC to 150 Hz.
Direct Modulation Input: 0.5 Vrms at 1 kHz or ±3 kHz deviation.
Direct Modulation Frequency range: DC to 5 kHz.