Daniels Electronics Ltd. MT-3 User manual

DANIELS
ELECTRONICS LTD.
TM
MT-3 RADIO SYSTEMS
MT-3 AM TRANSMITTER
MAIN BOARD
INSTRUCTION MANUAL
Covers:
A22-VAP130 AM Audio Processor Version 04
A21-TX3-00 TXMAIN/FPB Common Asembly Version 1.7
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: 3 Previous Issue: 2
Issue Date: December 98 Previous Issue Date: March 98 Daniels Electronics Ltd.
Printing Date: N/A Victoria, BC
Part No.: IM22-MT3AMTXMN PRINTED IN CANADA

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ii MT-3 AM Transmitter Main Board Instruction Manual
Reviewed By:
Quality Assurance:
Larry Freeman _________________
Name 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.

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MT-3 AM Transmitter Main Board Instruction Manual iii
TABLE OF CONTENTS
Page
1 GENERAL......................................................................................1-1
1.1 Introduction...........................................................................1-1
1.2 Performance Specifications.........................................................1-1
1.2.1 General.......................................................................1-1
1.2.2 Audio Specifications........................................................1-2
2 THEORY OF OPERATION ..................................................................2-1
2.1 MT-3 AM Transmitter Main Board ................................................2-1
2.1.1 General.......................................................................2-1
2.1.2 Transmitter Push-To-Talk..................................................2-1
2.1.2.1 Microphone PTT...................................................2-1
2.1.2.2 PTTWithTime-Out-Timer........................................2-2
2.1.2.3 PTT No Time-Out-Timer..........................................2-2
2.1.2.4 Optional Relay......................................................2-2
2.1.2.5 PTT Output .........................................................2-3
2.1.2.6 PTT Voltage Switching............................................2-3
2.1.2.7 Transmitter Standby Modes.......................................2-3
2.1.3 Audio Circuits...............................................................2-4
2.1.3.1 Microphone Audio.................................................2-5
2.1.3.2 Received Audio.....................................................2-5
2.1.4 Channel Selection ...........................................................2-5
2.1.4.1 Synthesized Transmitter...........................................2-5
2.1.4.2 Crystal Controlled Transmitter ...................................2-5
2.1.5 Amplifier Circuits...........................................................2-6
2.2 MT-3 Front Panel Board............................................................2-6
2.3 MT-3 AM Audio Processor.........................................................2-6
2.3.1 General.......................................................................2-6
2.3.2 Power Requirements........................................................2-6
2.3.3 Audio Circuitry..............................................................2-7
2.3.4 PTT Time-Out-Timer .......................................................2-8
3 TRANSMITTER ALIGNMENT.............................................................3-1
3.1 General ................................................................................3-1
3.2 Repair Note...........................................................................3-1
3.3 Printed Circuitboard Numbering Convention.....................................3-1
3.4 Recommended Test Equipment List ...............................................3-1
3.5 Standard Factory Settings and Jumper Configuration...........................3-2
3.5.1 MT-3 AM Transmitter Board Factory Configuration...................3-2
3.5.2 MT-3 AM Audio Processor Factory Configuration.....................3-3
3.6 MT-3 AM Transmitter Board Alignment ..........................................3-3

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iv MT-3 AM Transmitter Main Board Instruction Manual
3.6.1 General....................................................................... 3-3
3.6.2 MT-3 AM Transmitter Board Test Points................................ 3-4
3.7 Module Installation and Removal.................................................. 3-4
3.8 MT-3 AM Audio Processor Alignment ........................................... 3-5
3.8.1 General....................................................................... 3-5
3.8.2 MT-3 AM Audio Processor Adjustment ................................ 3-5
4 TRANSMITTERINTERCONNECTPINDEFINITIONS.............................. 4-1
5 ILLUSTRATIONS AND SCHEMATIC DIAGRAMS................................... 5-1
5.1 MT-3 AM Transmitter Block Diagram............................................ 5-1
5.2 MT-3 AM Transmitter Board Electrical Assembly............................... 5-3
5.2.1 MT-3AM Transmitter Main Board Component Layout (Top)........ 5-3
5.2.2 MT-3AM Transmitter Main Board Component Layout (Bottom)... 5-4
5.2.3 MT-3 AM Transmitter Main Board Schematic Diagram ............... 5-5
5.3 MT-3 Front Panel Board............................................................ 5-6
5.3.1 MT-3 Front Panel Board Component Layout........................... 5-6
5.3.2 MT-3 Front Panel Board Schematic...................................... 5-7
5.4 MT-3 AM Audio Processor Electrical Assembly ................................ 5-8
5.4.1 MT-3 AM Audio Processor Component Layout........................ 5-8
5.4.2 MT-3 AM Audio Processor Schematic Diagram........................ 5-9
6 PARTSLISTS................................................................................. 6-1
6.1 Transmitter Main Board Parts List................................................. 6-1
6.1.1 Transmitter Main Board Electrical Parts List............................ 6-1
6.1.2 Transmitter Main Board Mechanical Parts List.......................... 6-3
6.1.3 MT-3 Front Panel Board Electrical Parts List........................... 6-4
6.2 MT-3 AM Audio Processor Parts List ............................................ 6-4
6.2.1 MT-3 AM Audio Processor Electrical Parts List........................ 6-4
7 REVISION HISTORY........................................................................ 7-1

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MT-3 AM Transmitter Main Board Instruction Manual 1-1
1 GENERAL
1.1 Introduction
The MT-3 AM Transmitter Main Board integrates the MT-3 Front Panel Board, MT-3 AM Audio
Processor, Synthesizer or Crystal Control module and Amplifier module together to make a
working MT-3 AM series transmitter (see section 5.1: MT-3 AM 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 Control 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 to the 48 pin type 'F' connector on the rear of the Transmitter Main Board and are routed to
the other modules. The front and rear back plates are attached to the Transmitter Main Board and
together with the extruded aluminum shell, as discussed in the assembly section of the Transmitter
Manual, form the transmitter enclosure.
1.2 Performance Specifications
1.2.1 General
Type: MT-3 AM Series Transmitter
Compatibility: VT-3A Series Amplifier, OCT-3 Crystal Oscillator, OST-3
Frequency Synthesizer.
Modulation: 6K00A3 (Amplitude Modulation)
Operating Temperature Range: -30˚C to +60˚C, optional - 40˚C temperature test.
Operating Humidity: 95% RH (non-condensing) at +25°C.
Operating Voltage: +13.8Vdc , +9.5 Vdc Regulated.
Front Panel Control: One 3 position switch
• NORM (repeat mode)
• OFF
• KEY TX
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.).

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1-2 MT-3 AM Transmitter Main Board Instruction Manual
1.2.2 Audio Specifications
Audio Input: -30 to 0 dBm into a 600Ωbalanced load.
Audio Response: Flat audio; +1/-3 dB: 300 Hz - 3 kHz
Audio Distortion: Less than 3% -40˚C to +60˚C at 30% modulation
Less than 5% -40˚C to +60˚C at 90% modulation

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MT-3 AM Transmitter Main Board Instruction Manual 2-1
2 THEORY OF OPERATION
2.1 MT-3 AM Transmitter Main Board
2.1.1 General
Switch SW1 on the Front Panel Board is a DPDT switch which controls the operation of the
transmitter as discussed in the operations section of the Transmitter Manual. When SW1 is in the
'OFF' position the transmitter is turned off; however, +13.8 Vdc is still present on the Transmitter
Main Board as the +13.8 Vdc supply is not switched. When SW1 is in the 'KEYED' position,
+9.5 Vdc is supplied to the transmitter circuitry and the transmitter is continuously turned on.
When SW1 is in the 'NORM' position, +9.5 Vdc is supplied to the transmitter circuitry and the
transmitter can be keyed from several Push-To-Talk inputs.
Refer to section 5.2.3 Transmitter Main Board Schematic Diagram".
2.1.2 Transmitter Push-To-Talk
All three of the Push-To-Talk (PTT) inputs that key the transmitter are active low (< +2.0 Vdc).
One PTT input is on the front panel microphone connector. The other two PTT inputs: PTT WTO
(PTT With Time-Out-Timer) and PTT NTO (PTT No Time-Out-Timer), are on the backplane
connector of the transmitter board. If required, the microphone's PTT input can be configured to
activate the transmitter's Time-Out-Timer (TOT). An isolated PTT input can be made available by
installing an optional relay (RELAY1) and configuring jumpers J2 to J4 so that the relay controls
the PTT circuitry.
2.1.2.1 Microphone PTT
Jumper J1 on the MT-3 Front Panel Board configures the microphone's PTT input (MIC PTT) to
either bypass or activate the transmitter's TOT. Soldering jumper J1 in the 'x' position (default)
selects the MIC PTT NTO line which bypasses the TOT. Soldering J1 to the 'y' position selects
the MIC PTT WTO line which activates the transmitter's TOT. When SW1 is in the 'KEYED'
position the MIC PTT NTO line is automatically grounded. Refer to Section 5.3.1, "MT-3 Front
Panel Board Component Layout" for the location of jumper J1.

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2-2 MT-3 AM Transmitter Main Board Instruction Manual
2.1.2.2 PTT With Time-Out-Timer
Pins B10 and Z10 of the backplane connector are the PTT WTO input. When the PTT WTO
signal, which is normally high, falls below +2.0 Vdc, the transmitter is keyed. The transmitter is
disabled when the PTT WTO input rises above +2.3 Vdc or if the TOT's time-out period is
exceeded. If the time-out period is exceeded the PTT WTO input must go high (>+2.3 Vdc) and
then low again in order to rekey the transmitter.
The PTT WTO threshold of approximately +2 Vdc (0.3 Vdc hysteresis) is set by U1a, R1, R2,
R3, R4, R9, and R10 while diodes D1 and D2 provide overvoltage protection for U1a. The PTT
WTO signal output from U1a is 'AND'ed with the MIC PTT WTO by U2a. When either the PTT
WTO or the MIC PTT WTO is activated the output of U2a goes low which triggers the
transmitter's TOT located on the MT-3 Audio Processor. The TOT's output is 'AND'ed with the
MIC PTT NTO signal (U2c) and the PTT NTO signal (U2d). When any one of the preceding
three signals (TOT's output, MIC PTT NTO, PTT NTO) go low the transmitter is activated by
transistors Q1 to Q7 which switch power to the various modules.
2.1.2.3 PTT No Time-Out-Timer
Pins B14 and Z14 of the backplane connector are the PTT NTO input. When the PTT NTO signal,
which is normally high, falls below +2.0 Vdc, the transmitter is keyed. As long as the PTT NTO
signal remains below +2.0 Vdc the transmitter will remain keyed. The transmitter is disabled when
the PTT NTO signal rises above +2.3 Vdc.
The PTT NTO threshold of approximately +2 Vdc (0.3 Vdc hysteresis) is set by U1b, R5, R6,
R7, R8, R9, and R10 while diodes D3 and D4 provide overvoltage protection for U1b. The PTT
NTO signal is 'AND'ed with the output of U2c (MIC PTT NTO signal 'AND'ed with the TOT
output) by U2d. When the output of U2d goes low the transmitter is activated by transistors Q1 to
Q7 which switch power to the various modules.
2.1.2.4 Optional Relay
The transmitter's PTT circuitry can be completely isolated by installing RELAY1. Jumpers J2 to
J4 configure the relay to provide an isolated PTT input for either the PTT WTO line or PTT NTO
line. The isolated PTT input is enabled by energizing the relay. The transmitter board will accept
any of the Aromat TF2E line relays. These relays are DPDT, single side stable, and have coil
voltages ranging from +3 Vdc to +48 Vdc. Only one set of relay contacts are used to activate the
PTT circuitry, the other set of contacts are brought out to the backplane connector.
To configure the isolated input for PTT WTO operation jumpers J2, J4 must be in the 'y'position,
J3 must be in the 'x' position. In this mode, pins B10 and Z10 no longer function as the PTT
WTO input; however, pins B14 and Z14 continue to function as the normal PTT NTO input.

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MT-3 AM Transmitter Main Board Instruction Manual 2-3
To configure the isolated input for PTT NTO operation jumpers J2, J4, must be in the 'x' position
J3 must be in the 'y' position. In this mode, pins B14 and Z14 no longer function as the PTT NTO
input; however, pins B10 and Z10 continue to function as the normal PTT WTO input.
2.1.2.5 PTT Output
Pin B24 on the backplane connector is an open drain output (Q9) which is pulled low anytime the
transmitter is keyed and the synthesizer is locked. A crystal controlled transmitter does not have a
locked condition so pin B24 is pulled low anytime the transmitter is keyed. Q9, an N-channel
MOSFET capable of sinking currents up to 2 Amps, is activated by Q8 which is activated by the
Qualified PTT signal (JS2-6) of the synthesizer or crystal control module. The Qualified PTT
signal also controls the LED ENA line for diode D1 on the front panel board and enable line for the
VT-3A Amplifier Module (JP1-1).
2.1.2.6 PTT Voltage Switching
The PTT voltage switching circuitry is comprised of transistors Q1 through Q7 and the associated
resistors. The base of Q1 is driven by the output of U2d which is the combined PTT signal from
all of the PTT inputs. When the transmitter is keyed, Q1 is turned off and subsequently transistors
Q3, Q4, and Q6 are turned on. Transistors Q3, Q4, and Q6 provide three different functions:
•Q3 provides the active low signal for the synthesizer or crystal module PTT input;
•Q4 turns on Q5 which turns on the +9.5 Vdc Switched supply;
•Q6 turns on Q7 which turns on the +9.5 Vdc PTT Switched supply.
The '+9.5 Vdc Switched' supply (Q5) can also be activated by installing jumper J6 or by externally
grounding the TX Standby Line (pins B12 and Z12). The '+9.5 Vdc PTT Switched' supply and
the '+9.5 Vdc Switched' supply both provide +9.5 Vdc but depending on how jumpers J6, J7 and
J18 are configured the transmitter's standby mode will change.
2.1.2.7 Transmitter Standby Modes
The VT-3A130 Transmitter has four different standby modes that trade-off standby current
consumption for start-up speed. The standby modes are determined by three jumpers: jumper J6
which always turns on the '+9.5 Vdc Switched' supply, jumper J7 which selects the power source
for the MT-3 AM Audio Processor and jumper J18 which selects the enable line for the OST-
3A128 Synthesizer or OCT-3 Crystal Control Module.
The actual current and start-up time may depend on the frequncy controlled source (crystal or
synthesizer) and amplifier module. The current and start-up times given below are representative
values intended only as a guideline.

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2-4 MT-3 AM Transmitter Main Board Instruction Manual
•MODE 1:Jumper J6 out
- the audio processor is switched by a PTT signal
- the synthesizer or crystal module is switched by a PTT signal
- standby current: Synthesized - typically 13 mA
Crystal Controlled - typically 6 mA
- start-up time: Synthesized - typically 40 ms
Crystal Controlled - typically 40 ms
•MODE 2:Jumper J6 in, jumper J7 in the 'y' position, jumper J18 in the 'x' position
- the audio processor is switched by a PTT signal
- the synthesizer or crystal module is enabled all of the time
- standby current: Synthesized - not used in this mode
Crystal Controlled - typically 6 mA
- start-up time: Synthesized - not used in this mode
Crystal Controlled - typically 40 ms
• MODE 3:Jumper J6 in, jumper J7 in the 'x' position, jumper J18 in the 'y' position
- the audio processor is enabled all of the time
- the synthesizer or crystal module is switched by a PTT signal
- standby current: Synthesized - typically 19 mA
Crystal Controlled - typically 11 mA
- start-up time: Synthesized - typically 40 ms
Crystal Controlled - typically 8 ms
•MODE 4:Jumper J6 in, jumper J7 in the 'x' position, jumper J18 in the 'x' position
- the audio processor is enabled all of the time
- the synthesizer or crystal module is enabled all of the time
- standby current: Synthesized - typically 163 mA
Crystal Controlled - typically 23 mA
- start-up time: Synthesized - typically 12 ms
Crystal Controlled - typically 8 ms
2.1.3 Audio Circuits
All of the audio signal conditioning (e.g. limiting, filtering) is performed by the MT-3 AM Audio
Processor. The transmitter board routes the audio lines from the backplane connector to the audio
processor. The audio lines routed to the audio processor are: a 600 ohm balanced input (pins B18
and Z18), and a MIC AUDIO from the MT-3 FRONT PANEL BOARD. It is here that the MIC
audio is processed in the same manner as the 600 ohm balanced audio.
The audio processor's balanced input pins are isolated from pins B18 and Z18 by a transformer
(T1). Two audio outputs from the MT-3 AM Audio Processor are routed to the VT-3A130
Amplifier.

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MT-3 AM Transmitter Main Board Instruction Manual 2-5
2.1.3.1 Microphone Audio
Normally the audio from a transmitter's microphone is transmitted by that transmitter; however, the
Transmitter Main Board can be configured by the MIC IN and MIC OUT lines so that the audio
from an external microphone modulates transmitter. The configuration of the MIC IN (pin Z4) and
MIC OUT (pin B4) lines on the MT-3 Transmitter Board are controlled by jumpers J16 and J17
respectively. Jumper J16 selects the audio source for the MT-3 AM Audio Processor's
microphone input. Jumper J17 is used to enable or disable the MIC OUT line. Normally the
transmitter's microphone is selected (J16 in the 'x' position) and the MIC OUT line is enabled (J17
is installed).
2.1.3.2 Received Audio
Pin B20 is the audio input from the transmitter's corresponding receiver. The default setting for
this line is to have it AC coupled (Jumper J9 is out) and directly connected to the front panel board
RX AUDIO line.
2.1.4 Channel Selection
2.1.4.1 Synthesized Transmitter
Eight backplane connections are used to communicate with the synthesizer unit. Pins D28, D30,
and D32 are used (in house) to program the synthesizer. Channel select lines (pins D20, D22,
D24, and D26) are used once the synthesizer is programmed to select one of 16 channels. If the
channel select lines are all low (channel 0) the channel for the synthesizer is read from switches
FSW1 (most significant), FSW2, FSW3, and FSW4 (least significant). Since the resulting
frequency is dependent on the transmitter model, refer to the section on frequency selection in the
Transmitter Manual or to the channel designation tables for that particular transmitter.
2.1.4.2 Crystal Controlled Transmitter
The crystal control module is a direct replacement for the synthesizer module and therefore uses the
same connections as the synthesizer to connects to the MT-3 AM Transmitter Main Board. The
channel select lines and switches FSW1 to FSW4 are not used by the crystal control module as the
transmitter's operating frequency is determined by the crystal control module's crystal frequency.
A frequency multiplication factor, described in the manual for this module, relates the crystal
frequency to the operating frequency .

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2-6 MT-3 AM Transmitter Main Board Instruction Manual
2.1.5 Amplifier Circuits
The MT-3A series Amplifier has 5 connections that are cabled to the transmitter board: +13.8
Vdc, +9.5 Vdc, Enable, Mod and Gnd. The +13.8 Vdc supply (JP1-3) is always on while the
+9.5 Vdc supply (JP1-2) is always switched by a PTT signal. The enable line (JP1-1) is active
low and is controlled by the Qualified PTT signal from the synthesizer.
Jumpers J12, J13, J14, and J15 are not installed.
2.2 MT-3 Front Panel Board
The MT-3 Front Panel Board is a subsection of the MT-3 AM Transmitter Board which is used to
mount the front panel switch, diode, and microphone connector. The main purpose of the board is
to eliminate a wiring harness for the front panel components. Jumper J1, located on the rear of the
circuitboard, is used to select whether or not the MIC PTT line activates the transmitter's TOT:
•Jumper J1: 'x' position MIC PTT NTO no time-out-timer (factory setting)
'y' position MIC PTT WTO with time-out-timer
Refer to section 5.3.2 "MT-3 Front Panel Board Schematic Diagram".
2.3 MT-3 AM Audio Processor
2.3.1 General
The MT-3 AM Audio Processor is a versatile circuitboard that can provide several types of audio
processing. The module also has an on-board programmable push-to-talk (PTT) time-out-timer
(TOT) on an attached circuitboard. A continuous +9.5 Vdc supply and a continuous +13.8 Vdc
supply together with a switched +8.0 Vdc supply are required to power the module. Refer to
section 5.4.1 "MT-3 AM Audio Processor Component Layout" and to section 5.4.2 "MT-3 AM
Audio Processor Schematic Diagram" for component location and designation references.
2.3.2 Power Requirements
The audio processor can be configured for continuous audio standby or for switched audio standby
by the Transmitter Main Board. If fast audio risetime is desired, the transmitter should be operated
in standby mode 3 or 4 as specified in section 2.1.2.7. The current for the associated TOT is
approximately 4 mA when the transmitter is keyed.

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MT-3 AM Transmitter Main Board Instruction Manual 2-7
2.3.3 Audio Circuitry
The MT-3 AM Tx Audio Processor refer to section 5.4.2 "MT-3 AM Audio Processor Schematic
Diagram" has two audio inputs (Microphone input and Balanced input) which can be used to
modulate the transmitter. The input signals are combined by R2 and R17 at a compandor U1.
U1b controls the input level and makes gain inversely proportional to the input level (say a 20 dB
drop in input level will produced a 20 dB increase in gain). The output will remain fixed at a
constant level without clipping and distortion. (Automatic Level Control) The input signals are
adjusted by the pots R1, R16. The variable gain cell in U1a is used as a voltage-controlled
amplifier so that if the power supply (13.8Vdc) has changed the output level will change in order
to keep the modulation of the RF output signal at the same level. The gain control can be adjust by
the pot R4. (Automatic Modulation Control) The audio signal then amplifies and filters at U2.
The output signal is adjusted by the pot R9.

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2-8 MT-3 AM Transmitter Main Board Instruction Manual
2.3.4 PTT Time-Out-Timer
The PTT time-out-timer (TOT) is a relatively independent circuitry located on the Transmitter
Board. The TOT is powered from the continuous +9.5 Vdc supply (J34) and is programmable for
various time-out periods. The TOT input is normally high and in this state the timer is disabled.
When the input trigger level falls below +2.0 Vdc, the timer is activated, and the transmitter is
keyed. If the input trigger rises above +2.4 Vdc or if the time-out period is exceeded, the output
trigger will go high, disabling the transmitter. If the time-out period is exceeded, the TOT input
trigger must go high and then low again in order to rekey the transmitter.
The time-out duration is jumper selectable from 1 second to 8 hours. The table below shows the
time-out duration in minutes for the various jumper settings which are listed as enabled (E: jumper
shorted - in) or disabled (D: jumper left open - out). The standard factory setting of 5 minutes is
shown in bold type in the table below.
D = DISABLED (no solder jumper installed), E = ENABLED (solder jumper installed). Bold text
represents default settings.
TIME-OUT DURATION
(MINUTES)
JU26= E JU26= DJU26= E
JU32 JU31 JU29 JU28 JU27= D JU27= EJU27= E
E E E E 0.01 0.01 0.01
E E E D 0.02 0.03 0.01
E E D E 0.04 0.06 0.02
E E D D 0.08 0.12 0.05
E D E E 0.15 0.23 0.10
E D E D 0.31 0.47 0.19
E D D E 0.62 0.94 0.38
E D D D 1.25 1.88 0.75
D E E E 2.5 3.75 1.5
DEED 5.0 7.5 3.0
DEDE 10 15 6.0
D E D D 20 30 12
DDEE406024
D D E D 80 120 48
D D D E 160 240 96
D D D D 320 480 192

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MT-3 AM Transmitter Main Board Instruction Manual 3-1
3 TRANSMITTER ALIGNMENT
3.1 General
Transmitter alignment is simplified by using an M-3 Subrack, SM-3 System Monitor, and RF
extender cable to provide transmitter power and signal interconnection. Alternatively, +9.5 Vdc
and +13.8 Vdc may be applied directly to a transmitter module through positive connection for the
+9.5 Vdc to pins B6 and Z6, for the +13.8 Vdc to pins B2 and Z2, and negative connection to pins
B30, Z30, B32, and Z32. Transmitter balanced audio (600 Ω) is available at pins B18 and Z18.
3.2 Repair Note
MT-3 Transmitter modules are mainly made up of surface mount devices which should not be
removed or replaced using an ordinary soldering iron. Removal and replacement of surface mount
components should be performed only with specifically designed surface mount rework and repair
stations complete with ElectroStatic Dissipative (ESD) protection.
3.3 Printed Circuitboard Numbering Convention
To ease troubleshooting and maintenance procedures, Daniels Electronics Limited has adopted a
printed circuitboard (PCB) numbering convention in which the last two digits of the circuitboard
number represent the circuitboard version. For example:
• PCB number 43-9120 10 indicates circuitboard version 1.0;
• PCB number 50002- 02 indicates circuitboard version 2.0.
All PCB's manufactured by Daniels Electronics are identified by one of the above conventions.
When removing Surface Mount Solder Jumpers, it is recommended to use solder braid in place of
manual vacuum type desoldering tools when removing jumpers. This will help prevent damage to
the circuitboards.
3.4 Recommended Test Equipment List
Alignment of the complete transmitter requires the following test equipment or its equivalent. It is
assumed that any adjustment of the Transmitter Main Board will also involve the other modules.
Dual Power Supply: Regulated +9.5 Vdc at 2 A.
Regulated +13.8 Vdc at 2 A - Topward TPS-4000
Oscilloscope / Multimeter: Fluke 97 Scopemeter
Current Meter: Fluke 75 Multimeter

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3-2 MT-3 AM Transmitter Main Board Instruction Manual
Radio communications test set : Marconi Instruments 2955R
VSWR 3:1 mismatch load: JFW 50T-035-3.0:1
Alignment Tool: Johanson 4192
It is recommended that the radio communications test set be frequency locked to an external
reference (WWVH, GPS, Loran C) so that the high stability oscillator may be accurately set to
within its ±1 ppm frequency tolerance.
3.5 Standard Factory Settings and Jumper Configuration
Standard factory settings and the associated jumper configuration for each module of the
MT-3 AM series transmitter are given below.
3.5.1 MT-3 AM Transmitter Board Factory Configuration
The MT-3 AM Transmitter Main Board is factory configured as follows:
• Transmitter standby mode 3
• Optional relay not installed.
The corresponding jumper settings are:
•Jumper J2: 'x' position Optional relay configuration
•Jumper J3: not installed Optional relay configuration
•Jumper J4: 'y' position Optional relay configuration
•Jumper J6: installed Transmitter standby mode select - Mode 3
•Jumper J7: 'x' position Audio processor standby mode select
•Jumper J9: not installed Receiver audio ac/dc input coupling
•Jumper J12: not installed Not applicable
•Jumper J13: not installed Not applicable
•Jumper J14: not installed Not applicable
•Jumper J15: not installed Not applicable
•Jumper J16: 'x' position Microphone configuration
•Jumper J17: installed Microphone output line
•Jumper J18: 'y' position Synthesizer or crystal module standby mode select
•Jumper J19: 'x' position 600Ωaudio transformer bypass
•Jumper J20: 'x' position 600Ωaudio transformer bypass
•Jumper J21: not installed +8 Vdc audio processor supply bypass
•Jumper J22: 'x' position 600Ωaudio transformer bypass
•Jumper J23: 'x' position 600Ωaudio transformer bypass
•Jumper J24: not installed Not applicable
•Jumper J25: 'y' position AM Modulation mode
•Jumper J26: installed TOT configuration

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MT-3 AM Transmitter Main Board Instruction Manual 3-3
•Jumper J27: not installed TOT configuration
•Jumper J28: not installed TOT configuration
•Jumper J29: installed TOT configuration
•Jumper J31: installed TOT configuration
•Jumper J32: not installed TOT configuration
•Jumper J33: installed TOT input
•Jumper J34: installed TOT power supply
•Jumper J35: installed TOT output
3.5.2 MT-3 AM Audio Processor Factory Configuration
The MT-3 AM Tx Audio Processor is factory configured as follows:
•Microphone Input: 1kHz tone at -10 dBm gives 50% maximum modulations.
•Audio Balanced Input: 1 kHz tone at -8 dBm gives 90% maximum modulations.
•Automatic Modulation Control enabled
•Automatic Level Control enabled
The corresponding jumper settings are:
•Jumper JU1: 'y' position Automatic Modulation Control enabled
•Jumper JU2: not installed Modulation configuration
•Jumper JU3: 'y' position Automatic Level Control enabled
•Jumper JU4: not installed Time-out-time power supply (optional)
•Jumper JU5: 'y' position Voice application
•Jumper JU6: 'y' position Voice application
•Jumper JU7: not installed Modulation configuration
•Jumper JU8: 'y' position Automatic Level Control enabled
•Jumper JU9: installed Power AMC and Microphone enabled
3.6 MT-3 AM Transmitter Board Alignment
3.6.1 General
Before proceeding with the transmitter alignment, check that the appropriate jumpers are installed.
The standard jumper configuration for the Transmitter Main Board, given in section 3.4.1, is
normally employed for transmitter alignment. In a standard configuration, the only alignment
required on the MT-3 AM Transmitter Main Board for a synthesized transmitter is to set the
frequency switches (FSW1, FSW2, FSW3, and FSW4) for the desired channel frequency. FSW1
is the most significant digit of the frequency switches. The switch settings for the desired channel
frequency can be found in the channel designation tables. If the transmitter is using a crystal
control module, the switch settings are irrelevant.

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3-4 MT-3 AM Transmitter Main Board Instruction Manual
3.6.2 MT-3 AM Transmitter Board Test Points
TP1: not used
TP2: microphone audio
TP3: microphone PTT WTO; inactive +9.5 Vdc, active 0 Vdc
TP4: microphone PTT NTO; inactive +9.5 Vdc, active 0 Vdc
TP5: +9.5 Vdc from backplane connector
TP6: +9.5 Vdc from front panel board
TP7: +9.5 Vdc Switched
TP8: Qualified PTT; inactive +9.5 Vdc, active 0 Vdc: activated by synthesizer
TP9: synthesizer enable; selected by J18
TP10: synthesizer bootstrap line; +5 Vdc
TP11: synthesizer PTT input; inactive +9.5 Vdc, active 0 Vdc
TP12: audio processor TOT input; inactive +9.5 Vdc, active 0 Vdc
TP13: audio processor TOT output; inactive +9.5 Vdc, active 0 Vdc
TP14: audio processor audio output
TP15: not used
TP16: not used
TP17: not used
TP18: not used
TP19: audio processor continuous +9.5 Vdc
TP20: not used
TP21: audio processor supply +8 Vdc, selected by J7
TP22: not used
TP23: synthesizer receive data line; 0 Vdc
TP24: synthesizer transmit data line; +5 Vdc
TP25: Q1 collector; inactive 0 Vdc, active +9.5 Vdc
TP26: U2d output; inactive +9.5 Vdc, active 0 Vdc
TP27: U1a output (PTT WTO); inactive +9.5 Vdc, active 0 Vdc
TP28: U1b output (PTT NTO); inactive +9.5 Vdc, active 0 Vdc
TP29: Q6 collector / Q7 gate; inactive +9.5 Vdc, active 0 Vdc
TP31: +9.5 Vdc TOT SET
TP32: +9.5 Vdc TOT RESET
TP33: +9.5 Vdc BALANCED INPUT
TP34: +9.5 Vdc BALANCED INPUT
3.7 Module Installation and Removal
Installation of the Enhanced Synthesizer or Crystal Controlled Oscillator module is facilitated by
alignment pins on each corner of the module. When the four pins are aligned with their
corresponding hole in the Transmitter Main Board, push the module down, taking care to ensure
the connector pins on the bottom of the Synthesizer or Crystal Controlled Oscillator module are not
bent.

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MT-3 AM Transmitter Main Board Instruction Manual 3-5
To remove the Enhanced Synthesizer or Crystal Controlled Oscillator module, simply remove the
center screw from the module lid and pull the module out. The module should be pulled straight
out so that the four alignment pins do not bend or damage the circuitboard.
3.8 MT-3 AM Audio Processor Alignment
3.8.1 General
Verify the standard factory settings for the MT-3 AM Audio Processor as given in section 3.5.2
before beginning the standard modulation adjustment procedure. If the transmitter's channel
frequency changes, the audio processor should be realigned to optimize the transmitter's
performance. The schematic diagram for the audio processor is shown in section 5.4.2 and the
component layout is shown in section 5.4.1.
3.8.2 MT-3 AM Audio Processor Adjustment
**note: clockwise rotation of controls increase signal levels
1) Before adjusting the audio board, confirm that the transmitter frequency is correct.
2) Unscrew and slide out the case of the transmitter. Locate the Tx Audio Board.
3) Connect the transmitter RF Output to a Radio communications test set.
4) Connect the 600 ohm input to the incoming audio (pins B18, Z18). Set the audio
frequency to 1 kHz at the desired level of -8 dBm.
5) Turn the transmitter on.
6) Adjust the pot R16, in order to achieve about 0.700 Vrms at TP4.
7) Adjust the pot R14, in order to achieve about 0.200 Vrms at TP8.
8) Tune the Audio Adjust pot R1 on the Power Amplifier board to obtain 90%
modulation.
9) Apply a 1 kHz, -20 dBm input signal and adjust the pot R16 in order to obtain 30%
modulation.
10) Apply a 1 kHz, -8 dBm input signal, the modulation should be 90%, observe that the
distortion of the transmitted signal is within 5.0%.

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3-6 MT-3 AM Transmitter Main Board Instruction Manual
11) Slowly increase the input audio signal level to 5 dBm and observe that the modulation
does not go over 100%. This step verifies the correct operation of the ALC .
12) Change 13.8Vdc power supply to 10V and then to 17V, the modulation of the output
RF signal should remain at the same level of 90% ±7% and distortion should be less
then 3%. If not, adjust the pot R4 on the Audio Processor Board to achieve this.
This step verifies the correct operation of the AMC.
13) Repeat steps 7 and 9 if required.
14 Supply a 1 kHz, -10 dBm signal to the microphone input. (Note the level restriction
of -25 dBm to 0 dBm.)
15) Adjust the Microphone Input Level Adjust pot (R1) to achieve 50% of RF signal
modulation. Observe that the distortion should be under 5%.
16) Turn off the transmitter. Remove the signal source and replace all the screws.