User's Manual

PLL

CIRCUIT

DATA

CIRCUIT

SPEECH

CIRCUIT

VOX

KEYING

MODULE

ANALOGUE INPUT

DATA

MODE

Tx KEY

PSG/10280-1

DIGITAL

INPUT

RPT 633

Page 3 - 2 TM1184 Issue 1

CONTENTS: (Continued)

FIGURES Page

1. Block Diagram 3-2

2. Module Interconnection Diagram 3-6

3. Speech Call 3-8

4. Open Channel Speech 3-8

5. Switching Into Speech 3-9

6. Switching From Speech 3-10

_______________________

INTRODUCTION

1. The RPT 633 Transmitter accepts analogue or digital information which is

modulated onto an UHF signal. The transmitter output frequency is produced by

doubling the frequency of a voltage controlled oscillator (VCO). The VCO is locked

to a reference crystal oscillator which is frequency modulated by either the Data or

Audio input signals. A basic block diagram is shown at Figure 1.

Figure 1: Block Diagram

TRANSMITTER

Power Supplies

2. A nominal 17V DC power supply is fed into the board at SK3 where it is filtered

by L14, L15, L16, C67 and C68. Fixed voltage regulators IC3 and IC4 provide 12V

for the transmitter circuit and output transistor respectively, while regulator IC5

produces 5V for the transmitter and VOX Keying module. Integrated circuit IC2

produces 8.2V for the VCO and buffer amplifiers and IC11 acts as a voltage

converter to produce -11V from a 12V input.