User's Guide

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