9105 Aka X2/Codan X2 TSM Codan

User Manual: Pdf 9105 aka X2/Codan X2 TSM

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X-2 HF SSB Transceiver

Technical service manual

 1992, 1993 Codan Pty Ltd.

ACN 007 590 605

Order code 15-02047

Issue 2, October 1993

Head Office International Marketing Offices

Codan Pty Ltd

81 Graves Street

Newton

SOUTH AUSTRALIA 5074

Telephone

National 08 336 0311

International +61 8 336 0311

Facsimile 08 337 6090

Australia, Pacific and South East Asia

Codan Pty Ltd

Suite 24, 818 Pittwater Road

Dee Why

New South Wales

AUSTRALIA 2099

Telephone

National 02 971 2233

International +61 2 971 2233

Facsimile 02 982 1117

Telex 22631

Africa, Europe and The Middle East

Codan (U.K.) Ltd

6 Grove Park

Mill Lane

Alton, Hampshire GU34 2QG

UNITED KINGDOM

Telephone

National 0420 80121

International +44 420 80121

Facsimile 0420 541098

Telex 858355

North and South America

Codan Pty Ltd

Suite 101

8011 Leslie Road

Richmond BC V6X 7E4

CANADA

Telephone

National 604 270 8332

International +1 604 270 8332

Facsimile 604 270 4401

Publication No: 15-02047

Table of Contents

1Introduction........................................................................................................1-1

1.1 Purpose...........................................................................................................1-1

1.2 How this manual is organised ..........................................................................1-1

1.3 Conventions....................................................................................................1-2

1.4 Related Documents .........................................................................................1-2

1.5 Overview ........................................................................................................1-2

1.6 Specifications..................................................................................................1-3

1.6.1 General Specifications.................................................................1-3

1.6.2 Receiver Specifications...............................................................1-5

1.6.3 Transmitter Specifications...........................................................1-6

2Brief Description ............................................................................................2-1

2.1 General ...........................................................................................................2-1

2.2 Control and Switching.....................................................................................2-2

2.3 Synthesiser......................................................................................................2-2

2.4 Receive Path ...................................................................................................2-3

2.5 Transmit Path..................................................................................................2-4

3Operating Instructions...............................................................................3-1

4Technical Description ................................................................................4-1

4.1 Control and Supply Voltages...........................................................................4-2

4.1.1 Power.........................................................................................4-2

4.1.2 Supply Voltages .........................................................................4-2

4.1.3 Receive/Transmit Switching........................................................4-3

4.2 Receiver..........................................................................................................4-4

4.2.1 Input Filters................................................................................4-4

4.2.2 First Mixer..................................................................................4-4

4.2.3 45 MHz Roofing Filter................................................................4-4

4.2.4 Second Mixer .............................................................................4-4

4.2.5 Noise Limiter..............................................................................4-5

4.2.6 455 kHz Filter and IF Amplifier ..................................................4-5

4.2.7 Automatic Gain Control..............................................................4-6

4.2.8 Mute...........................................................................................4-7

4.2.9 Volume Control and Audio Amplifier .........................................4-8

ii Table of Contents X-2 Technical Service Manual

Publication No: 15-02047

4.3 Transmitter Exciter .........................................................................................4-8

4.3.1 Microphone Compressor.............................................................4-8

4.3.2 Modulator ..................................................................................4-9

4.3.3 455 kHz Filter and First Mixer....................................................4-9

4.3.4 45 MHz Roofing Filter................................................................4-9

4.3.5 Second Mixer and Exciter Output Filter......................................4-9

4.4 Local Oscillators ...........................................................................................4-10

4.4.1 Introduction..............................................................................4-10

4.4.2 VCO1 and PLL ........................................................................4-10

4.4.3 VCO2 and PLL ........................................................................4-11

4.4.4 455 kHz Local Oscillator..........................................................4-12

4.4.5 Clarifier ....................................................................................4-12

4.5 Micro and Peripherals ...................................................................................4-13

4.5.1 Microcontroller.........................................................................4-13

4.5.2 I2C Bus ....................................................................................4-13

4.5.3 PA Control Bus ........................................................................4-13

4.5.4 Front Panel Controls.................................................................4-14

4.5.5 Tune.........................................................................................4-15

4.5.6 Tone Generation.......................................................................4-15

4.5.7 A/D Inputs................................................................................4-15

4.5.8 Microcontroller Reset...............................................................4-16

4.6 PA and Filters ...............................................................................................4-16

4.6.1 Gain Control Stage...................................................................4-17

4.6.2 Predriver Stages .......................................................................4-17

4.6.3 Driver Stage .............................................................................4-17

4.6.4 Output Stage and Bias Regulator..............................................4-18

4.6.5 Output Filters and Antenna 1 and 2 Select ................................4-18

4.6.6 ALC Control ............................................................................4-18

5Maintenance.......................................................................................................5-1

5.1 Introduction....................................................................................................5-1

5.2 General ...........................................................................................................5-1

5.2.1 CMOS Devices...........................................................................5-1

5.2.2 Circuit Boards ............................................................................5-2

5.2.3 Transmitter Precautions..............................................................5-3

5.2.4 Probe Precautions.......................................................................5-4

5.3 Fault Diagnosis ...............................................................................................5-4

5.3.1 General.......................................................................................5-4

5.3.2 Voltage measurements................................................................5-5

5.3.3 No Reception .............................................................................5-6

X-2 Technical Service Manual iii

Publication No: 15-02047

5.3.4 Transmitter Failure .....................................................................5-7

5.3.5 Unlocked Synthesiser..................................................................5-7

5.3.6 PA Failure ..................................................................................5-8

5.4 Dismantling and Assembling............................................................................5-8

5.4.1. General.......................................................................................5-8

5.4.2 Top and Bottom Covers .............................................................5-9

5.4.3 Rx/Exciter & Control PCB .........................................................5-9

5.4.4 Front Panel PCB.........................................................................5-9

5.4.5 PA and Filter Assembly.............................................................5-10

5.4.6 Replacement of PA Transistors.................................................5-11

6Channel Additions.........................................................................................6-1

7Adjustments.......................................................................................................7-1

7.1 Introduction....................................................................................................7-1

7.2 Test Equipment Required................................................................................7-1

7.3 Voltage Regulators .........................................................................................7-1

7.4 Crystal Oven ...................................................................................................7-2

7.5 Test Mode ......................................................................................................7-2

7.6 VCO Checks and Adjustments ........................................................................7-4

7.6.1 VCO1 Check..............................................................................7-4

7.6.2 VCO2 Check..............................................................................7-4

7.6.3 VCO2 Adjust..............................................................................7-5

7.7 45 MHz Filter Alignment.................................................................................7-5

7.7.1 Alignment - Method 1.................................................................7-6

7.7.2 Alignment - Method 2.................................................................7-7

7.8 455 kHz IF and N/L Alignment .......................................................................7-7

7.9 Frequency Adjustment.....................................................................................7-8

7.9.1 Frequency Adjust USB ...............................................................7-8

7.9.2 Frequency Adjust LSB................................................................7-9

7.10 Mute Adjustment.............................................................................................7-9

7.11 PA Adjustments.............................................................................................7-10

7.11.1 Driver Bias ...............................................................................7-10

7.11.2 PA Bias ....................................................................................7-10

7.11.3 Output Power...........................................................................7-11

7.11.4 Intermodulation ........................................................................7-12

7.12 Receiver Performance Checks........................................................................7-13

7.12.1 Sensitivity and S+N/N ratio ......................................................7-13

7.12.2 AGC Check..............................................................................7-13

7.12.3 Audio Output ...........................................................................7-13

iv Table of Contents X-2 Technical Service Manual

Publication No: 15-02047

7.12.4 Selectivity (USB operation) ......................................................7-13

7.12.5 Clarifier Operation....................................................................7-14

7.12.6 Noise Limiter Operation ...........................................................7-14

7.13 Transmitter Performance Checks ...................................................................7-14

7.13.1 Frequency Check......................................................................7-14

7.13.2 ALC .........................................................................................7-15

7.13.3 Power Output and Intermodulation...........................................7-15

7.13.4 Emergency Call ........................................................................7-15

8Appendices.........................................................................................................8-1

Appendix A: Connectors ..........................................................................................8-1

A.1 Microphone................................................................................8-1

A.2 External Loudspeaker.................................................................8-1

A.3 Antenna Control .........................................................................8-2

A.4 Programming Cable ....................................................................8-2

A.5 Cloning Cable.............................................................................8-2

Appendix B: Parts Lists............................................................................................8-3

B.1 General Information....................................................................8-3

B.2 Ordering Information..................................................................8-4

B.3 Component Substitution .............................................................8-4

B.4 Parts Lists...................................................................................8-4

Appendix C: Engineering Drawings ........................................................................8-23

Appendix D: Glossary of Terms..............................................................................8-25

D.1 Abbreviations ...........................................................................8-25

D.2 Abbreviations of Units ..............................................................8-26

D.3 Abbreviations of Unit Multiples ................................................8-27

X-2 Technical Service Manual v

Publication No: 15-02047

List of figures

Figure Description Page No

2.1 X-2 PCB Block Diagram 2-1

7.1 Ripple Response 7-6

List of tables

Table Description Page No

2.1 Drawing Reference 2-1

3.1 Audible Warning Tones 3-2

4.1 Drawing Reference 4-1

4.2 Rx/Exciter PCB Supply Voltages 4-2

4.3 PA PCB Supply Voltages 4-2

5.1 Peak to Peak Voltages 5-8

7.1 USB/LSB Test Frequencies and Functions 7-3

7.2 Power Output PEP vs Measuring Instrument 7-11

A.1 Microphone Connector Pin Function 8-1

A.2 External Loudspeaker Connector Pin Function 8-1

A.3 Antenna Control Connector Pin Function 8-2

A.4 Programming Cable Connector Pin Function 8-2

A.5 Cloning Cable Connector Pin Function 8-2

B.1 Resistor and Capacitor Abbreviations 8-3

B.2 Parts List Index 8-4

C.1 List of Drawings 8-24

D.1 Abbreviations 8-26

D.2 Abbreviations of Units 8-27

D.3 Abbreviations of Unit Multiples 8-28

vi Table of Contents X-2 Technical Service Manual

Publication No: 15-02047

X-2 Technical Service Manual 1-1

Publication No: 15-02047

1Introduction

1.1 Purpose

The purpose of this manual is to provide a technical description, details and

drawings about the X-2 transceiver for the technician to understand the:

•function

•technical operation

•fault diagnosis

•dismantling and assembly

•setup and adjustment procedures

1.2 How this manual is organised

The X-2 Technical Service Manual is organised as follows:

Chapter 1 An overview of the features of the X-2 transceiver

including specifications.

Chapter 2 A brief description of the X-2 transceiver with a general

description of the major circuit functions for the control,

reception and transmission of signals.

Chapter 3 Operating instructions for the X-2 transceiver.

Chapter 4 A more detailed technical description of the operation

and circuit function of the X-2 transceiver. Read this

with the associated technical drawings found in the

appendices.

Chapter 5 Maintenance, general cautions and warnings, fault

diagnosis procedures associated with the maintenance of

the X-2 transceiver.

Chapter 6 Programming procedures for channel additions.

Chapter 7 Adjustments, checks and alignments to the X-2

Transceiver detailing required test equipment.

Chapter 8 Comprises four appendices. Connector tables, parts lists,

engineering drawings and glossaries.

Introduction 1-2X-2 Technical Service Manual

Publication No: 15-02047

1.3 Conventions

The X-2 transceiver is type approved in Australia as the 9105 transceiver. All

type approval documentation refers to it as the 9105. Throughout this

manual the transceiver is referred to as the X-2.

1.4 Related Documents

If there is a need to program the X-2, make reference to the XP

programming guide. This guide is available as a separate document, Codan

Part No:15-04035.

1.5 Overview

The X-2 is a 10 channel, high frequency single sideband (HF SSB)

transceiver suitable for use in fixed station or mobile applications.

The X-2 can be factory set or dealer programmed using the XP programming

system to select:

•operating frequencies

•mode of operation

•emergency calling

•one of two antenna output sockets.

This programming feature eliminates the need for crystals and discreet

channelling/customising components. Because operation on lower sideband

(LSB), upper sideband (USB) or Emergency Call (Royal Flying Doctor

Service RFDS - only in Australia) is software programmable, there is no

need for factory fitted hardware options.

Different audio tones indicate operating conditions or system faults such as:

•excessive VSWR

•tune complete or fail

•low or high supply voltage

•channel not programmed.

Where two channel networks are used, two separate antenna output sockets

on the rear panel allow the use of:

•individually tuned half-wave dipole base station antennas

•mobile whips.

This eliminates the need for antenna selectors or coaxial switches.

Users can clone the programmed information contained in the X-2 to another

transceiver by using the microphone socket. XP software is not required for

cloning.

X-2 Technical Service Manual Introduction 1-3

Publication No: 15-02047

1.6 Specifications

This section of the manual provides specifications for the X-2 transceiver in

the following categories:

•General Specifications

•Receiver Specifications

•Transmitter Specifications

The specification figures listed are the minimum standard for the X-2

transceiver and production models will equal or exceed these figures. Where

relevant, acceptance limits are shown in brackets.

Unless otherwise specified, all measurements have been made using

13.6 V DC, with 50 Ω source and load resistances at an ambient temperature

of 25°C.

1.6.1 General Specifications

Frequency Range 2 to 18 MHz.

Channel Capacity 10 channels. Any combination of single or dual

frequency simplex.

Frequency Generation Frequency synthesiser with 10 Hz resolution:

controlled by plug-in EEPROM.

Operating Modes Single sideband (J3E).

Programmable USB, LSB or front panel

switched.

Frequency Stability USB: ±2(3)ppm

LSB: ±(2(3)ppm +10 Hz) }-10°C to +60°C

Long term ageing 1ppm per year.

Crystal reference oven warm up time 1 minute.

Programming Frequencies and options are programmed via the

microphone socket and 3-wire RS232 interface

using XP programming software and an IBM

compatible PC.

Cloning Channel frequencies and options can be copied

from one transceiver to another via the

microphone socket.

Controls Power ON/OFF and Volume.

Channel select.

Clarifier.

Mode USB/LSB.

Mute ON/OFF/Tune.

Emergency Call: RFDS 880/1320 Hz. (Australia

only)

Introduction 1-4X-2 Technical Service Manual

Publication No: 15-02047

Indicators Power On/Transmit.

Connectors:

Front

Rear Microphone/Handset.

RF - UHF connectors: Qty 2 (programmable).

Antenna Control.

Extension Loudspeaker.

RF Input/Output

impedance

50 Ω nominal.

Supply Voltage 12 V DC nominal, negative earth.

Normal operating range 10.5 to 15 V.

Maximum operating range 9 to 16 V approx.

Reverse polarity protection.

Supply Current Receive : no signal 360 mA.

Transmit: refer to Transmit Specifications.

Environment Ambient Temp.

-10°C to +30°C

+30°C to +60°C

Relative Humidity

95%

From 95% at +30°C to

30% at +60°C

Derate upper ambient temperature by 1°C per

330 m above sea level.

Cooling Convection.

Size and Weight Transceiver only:

230 mm W x 75 mm H x 290 mm D 2.5 kg

With mounting cradle:

250 mm W x 90 mm H x 290 mm D 3.0 kg

Depth measurements include rear

connectors/cables.

X-2 Technical Service Manual Introduction 1-5

Publication No: 15-02047

1.6.2 Receiver Specifications

Type Dual conversion, superheterodyne.

IF Frequencies 45 MHz and 455 kHz.

Sensitivity 0.3(0.4) µV PD -117(-115) dBm for 10 dB

SINAD with > 50 mW audio output.

Input Protection Will withstand 50 V RF from 50 Ω.

Selectivity Greater than 70(65) dB at -1 kHz and +4 kHz

reference SCF USB.

Pass Band -6(-8) dB 300 to 2700 Hz

Ripple 2(4) dB pp 500 to 2500 Hz

Desensitisation 10 dB SINAD reduced to 7 dB SINAD.

-1 and +4 kHz (ref SCF) 65(60) dB

±10 kHz 85(80) dB

±50 kHz 100(95) dB

Image Rejection Better than 90(80) dB.

Spurious Responses Better than 90(70) dB.

Self Generated Signals > 0.3 µV PD:

3652, 5478, 7304, 9130, 10956, 14608 kHz.

Cross Modulation A signal 85(80) dB above a signal producing

10 dB SINAD, modulated 30% and removed at

least 20 kHz from the wanted signal will

produce an increase in receiver noise of less than

3 dB.

Blocking As for desensitisation.

Intermodulation To produce a third order intermodulation

product equivalent to a wanted signal producing

10 dB SINAD, two unwanted signals greater

than 30 kHz removed from the wanted signal

must have a level greater than 82(80) dB above

the wanted signal. Third order intercept +7(4)

dBm, not affected by AGC.

AGC Less than 6 dB variation in output for input

variation between 1.5(2.5) µV and 100 mV PD.

Fast attack, slow release.

AF Power and

Distortion 2.5 W into 8 Ω 5% THD

5.0 W into 4 Ω 5% THD

8.0 W into 2 Ω 5% THD.

Clarifier ±50 Hz up to 5 MHz

±10 ppm above 5 MHz

Clarifier is automatically reset to mid-frequency

with channel change.

Introduction 1-6X-2 Technical Service Manual

Publication No: 15-02047

1.6.3 Transmitter Specifications

Type All solid state.

Power Output 100 W PEP ± 0.5 dB may be internally set to

any output between 125 and 25 W PEP.

CW or single tone approx. 60% of PEP.

(Average ALC control).

Duty Cycle 100% normal speech.

Supply Current 2-tone/CW 8 to 12 A

Average speech 6 A

Average speech for battery life calculations.

Protection Safe under all load conditions by limiting

reflected power to 10 W PEP and limiting PA

transistor collector voltage swing.

Thermal protection against excessive heatsink

temperature.

AF Response Overall response of microphone and transmitter

rises approximately 6 dB/octave 300-2700 Hz.

Electrical input -6(8) dB, 300-2700 Hz.

Ripple 2(4) dB pp, 500-2500 Hz.

Spurious and

Harmonic Emissions 55(48) dB below PEP.

Carrier Suppression 60(50) dB below PEP.

Unwanted Sideband 50(45) dB below PEP (400 Hz).

70(65) dB below PEP (1 kHz).

Intermodulation

(2 tone test) 100 W 30(26) dB below each tone.

36(32) dB below PEP.

125 W 27(26) dB below each tone.

33(32) dB below PEP.

ALC A 10 dB increase in signal input above

compression threshold produces less than 0.5 dB

increase in power output.

Maximum ALC range greater than 30 dB.

ALC attack time approximately 1 ms.

Residual Noise 65(55) dB below PEP of selected channel.

Microphone Dynamic type with push-to-talk switch fitted in

the case.

X-2 Technical Service Manual 2-1

Publication No: 15-02047

2Brief Description

This section of the manual provides a brief description of the major

components and circuit functions of the X-2 transceiver as follows:

•Control and switching functions

•Synthesizer operation

•Receive path

•Transmit path

For an in-depth review of these functions refer to Chapter 4 "Technical

Description".

2.1 General

Read this description of the X-2 transceiver with the circuit drawing shown

in Table 2.1.

Title Circuit Diagram

X-2 Block Diagram 03-00876

Table 2.1: Drawing reference

The X-2 transceiver is a double conversion superheterodyne receiver. It uses

45 MHz and 455 kHz IF frequencies for the double conversion process. The

45 MHz roofing filter and the 455 kHz sideband filter are common to the

transmit and receive audio paths.

The transceiver can be programmed with channels for either single or dual

frequency simplex operation, and uses the double conversionError!

Bookmark not defined. process when transmitting or receiving.

The X-2's circuits and functions are located on three major PCBs as shown in

Figure 2.1.

•Front panel PCB and panel controls

•Rx/Exciter & Control Circuit PCB consisting of:

- RF and Dual synthesizer circuits

- 455 kHz IF and audio circuits

- Microprocessor and peripheral circuits

•PA and Filter PCB.

Front

Panel PA &

Filters

Receiver\Exciter

and Control

Figure 2.1: X-2 PCB Block Diagram

Brief Description 2-2X-2 Technical Service Manual

Publication No: 15-02047

The main elements of the X-2 can be divided into the control and switching

functions, the synthesizers used to produce the oscillator frequencies and the

signal paths taken in receive and transmit modes.

Circuit elements and functions common to both the transmit and receive

paths are the:

•45 MHz roofing filter

•455 kHz sideband filter

•local oscillators VCO1 and VCO2

2.2 Control and Switching

The switching and control voltages determine the path taken by the transmit

or receive signals through the transceiver.

Most of the transceiver functions are controlled by microcontroller IC403.

Channel frequencies and options are programmed via the microcontroller to

the Electrical Erasable Programmable Read Only Memory (EEPROM),

IC404. All other transceiver functions are pre-programmed in the

microcontroller's internal Read Only Memory (ROM).

The power on/off and volume controls are hardware functions and not

controlled by the microcontroller.The on/off switch is part of the volume

control and directly energises a power-on relay. A series diode provides

reverse polarity protection.

The volume control in the audio signal path connects the preamplifier (after

the demodulator) and the audio amplifier to drive the loudspeaker.

2.3 Synthesizer

The X-2 transceiver uses single loop synthesizers. The main synthesizer

(VCO1) generates an oscillator frequency of 47 MHz to 63 MHz i.e. 2 MHz

to 18 MHz plus 45 MHz, in 2 kHz steps.

The vernier synthesizer (VCO2) generates oscillator frequencies of

44.5435 MHz to 44.5455 MHz in 10 Hz steps.

The microcontroller IC controls the synthesizers by loading serial data into

both synthesizers. The data varies according to the required channel

frequency programmed into the memory.

When the upper sideband is selected, the X-2 uses one main reference

oscillator of 7304 kHz to produce 456.5 kHz (7304 kHz divided by 16). If

lower sideband is needed, a second crystal of 1814 kHz is used to provide

453.5 kHz (1814 kHz divided by 4).

X-2 Technical Service Manual Brief Description 2-3

Publication No: 15-02047

2.4 Receive Path

PA and Filter PCB

The received signal from the antenna passes through a PA low-pass filter to

the transmit/receive relay and broadcast filter on the PA PCB to the receiver

input on the main PCB.

Rx/Exciter & Control PCB

From the receive input, the signal is fed via a second 20 MHz low-pass filter

to the input of the first balanced mixer. Here it mixes with the local

oscillator VCO1 and converts to 45 MHz.

A 15 kHz roofing filter filters this 45 MHz signal before being applied to the

second balanced mixer. The signal mixes with a second local oscillator

VCO2 producing an IF signal centred on 455 kHz.

The output of the second mixer divides into two paths:

•the main path passes through a noise gate to a 2.5 kHz sideband filter

where only the wanted sideband passes to the high gain AGC controlled

IF amplifier.

•the second path passes the signal through an amplifier which detects

noise and controls the noise gate to remove impulse noise such as car

ignition from the 455 kHz signal.

The amplified 455 kHz signal is demodulated to produce an audio signal and

amplified. The amplified audio signal operates an AGC circuit. This

controls the IF amplifier gain to prevent overloading when receiving strong

signals. It is also used to maintain a constant audio output with changing

input signals.

After amplification the signal passes through a mute that removes the

receiver noise from the speaker when enabled. When speech is detected, the

gate in the audio line closes to allow the signal to be heard. The signal feeds

the volume control on the Front Panel PCB.

Front Panel PCB

The signal from the volume control is applied to a power amplifier IC2 to

drive the transceiver's loudspeaker.

Brief Description 2-4X-2 Technical Service Manual

Publication No: 15-02047

2.5 Transmit Path

Rx/Exciter PCB

The microphone amplifier/compressor IC303/306, amplifies and levels the

audio signal from the microphone and drives a balanced modulator IC301.

When mixed with the local oscillator, the double sideband output of the

modulator feeds a 2.5 kHz sideband filter centred on 455 kHz, passing only

the wanted sideband to the first mixer IC9. Here it mixes with the local

oscillator VCO2 to produce an IF signal of 45 MHz.

The 15 kHz wide roofing filter centred at 45 MHz filters the transmit signal

to remove unwanted mixed signals before it feeds the second mixer.

At the second mixer, the signal mixes with the oscillator VCO1 producing

the required channel frequency (2 MHz to 18 MHz) and passes through a

20 MHz low pass filter to the Power Amplifier & Filter PCB (PA PCB).

PA and Filter PCB

The PA assembly amplifies the signal, passes it on to the transmit/receive

relay, and then to the selected band filter. At the filter output it continues to

the VSWR detector. The detector monitors the forward and reflected power

and controls the power output of the transmitter. If a high VSWR is

detected, the power output reduces to protect the power amplifier.

A coaxial cable connects the signal to the appropriate antenna for

transmission.

X2 Technical Service Manual 3-1

Publication No: 15-02047

3Operating Instructions

This section of the maual describes how to operate the X-2 Tansceiver in

both normal and RFDS Emergency Call (Australia only) modes. Table 3.1

provides an explanation of the meaning of audible tones. To operate the X-2:

1. Switch the transceiver on by turning the Volume control clockwise

until the indicator lamp lights.

2. Select the required Channel and USB or LSB mode.

3. If using a broadband or dipole antenna go to step 5.

4. After selecting the required channel:

(i) Where a multi-frequency tapped whip is used, select the correct

tap position for the frequency in use.

(ii) Where an automatic antenna tuner is used, select Tune for

approximately one second and ensure the "tune complete",

double high beep is heard.

(iii) Where a manual antenna tuner is being used, set the tuner

controls to the logging scale positions. Before transmitting

operate the Tune switch and adjust the Tune control on the

front panel for maximum meter reading.

5. With the Mute switch in the Off position, set the Volume control to a

comfortable listening level. The mute function removes background

noise when no signals are present and should be switched Off to

prevent occasional loss of syllables when communicating in the

presence of weak signals.

6. Adjust the Clarifier to obtain a better speech quality if necessary.

7. Listen before transmitting to ensure that the selected Channel is free

of traffic.

8. Hold the Microphone side-on, close to the mouth. Press the

Transmit button and speak clearly.

9. When transmitting, the Indicator light will flicker. Tune will cause the

Indicator to light continuously.

10. Audible tones are provided to inform the operator of equipment status

or provide an operating error warning as shown in Table 3.1.

Operating Instructions 3-2X-2 Technical Service Manual

Publication No: 15-02047

BEEPS CONTINUOUS

Low Tone High Tone Low Tone High Tone

Single Transmit

inhibited Channel

unavailable High supply

voltage

Double Tune Fail

(check

antenna)

Double Tune

complete

Slow repetitive Low supply

voltage Repetitive Channel not

programmed

Fast repetitive PTT time out

Table 3.1: Audible Warning Tones

11. If making an RFDS Emergency Call (Australia only) carry out the

steps as outlined in 1 to 5 and proceed as follows:

(i) Ensure a local RFDS channel has been selected - on other

channels the call will not be transmitted.

(ii) Operate Emgcy Call switch for at least 15 seconds then wait for

a reply before transmitting. Unattended RFDS base stations will

transmit a tone within 90 seconds if the call has been received.

ICAUTION

1. Do not obstruct the free flow of air through the transceiver rear fins.

2. If using two antennas, connect them to the correct antenna sockets for

the frequency being used.

X2 Technical Service Manual 4-1

Publication No: 15-02047

4Technical Description

This section of the manual contains a technical description of the X-2

transceiver and should be read together with the drawings shown in

Table 4.1.

Description Circuit Diagram PCB Assembly

Rx/Exciter & Control 04-02907 (3 sheets) 08-04840

-RF and Dual Synthesizer Sheet 1

-455 kHz IF and Audio Sheet 2

-Micro and Peripherals Sheet 3

PA and Filter 04-02908 08-04841

Front Panel 04-02909 08-04842

Table 4.1: Drawing reference Directory

Circuit components on the Rx/Exciter PCB are numbered according to the

following system:

•Sheet 1: 1 to 299

•Sheet 2: 301 to 399

•Sheet 3: 401 to 499

A prompt to use a particular drawing will appear as a symbol in the text.

For example:

104-02907 sheet 1 indicates that you should use sheet 1 of drawing

number 04-02907.

As an additional help a general location guide has been provided to indicate

where to find certain circuit elements described in the text.

For example:

IC302[D5] can be found in the vicinity of row D and column 5.

Technical Description 4-2X-2 Technical Service Manual

Publication No: 15-02047

4.1 Control and Supply Voltages

All switching, except power on, is controlled either directly or indirectly by

the microcontroller located on the Rx/Exciter PCB.

4.1.1 Power

104-02909

When contact S1[D2] (part of volume control assembly) on the front panel is

closed, [104-02908] a ground is applied to relay K8[C10] on the PA assembly via

interconnecting cables between the Front panel, Rx/Exciter, and the PA

assembly. K8 relay energises and closes contacts K8-1[D11], applying the DC

supply to the Transceiver.

Diode D5 in series with K8 prevents the relay from energising should the

supply be accidentally connected in reverse.

4.1.2 Supply Voltages

The supply voltages used on the Rx/Exciter PCB are shown in Table 4.2.

Supply Description Regulator

'A' rail unregulated battery supply

'B' rail +10 V regulated supply IC401

+5VA 5 V regulated supply IC3

+5VB 5 V regulated supply IC402

Table 4.2: Rx/Exciter PCB Supply Voltages

The supply voltages used on the PA PCB are shown in Table 4.3.

Supply Description Regulator

'A' rail unregulated battery supply

+5V 5 V regulated supply selected in transmit only IC2

+5V 5 V supply to IC1 V1

Table 4.3: PA PCB Supply Voltages

X-2 Technical Service Manual Technical Description 4-3

Publication No: 15-02047

4.1.3 Receive/Transmit Switching

104-02907 sheet 3

The microcontroller IC403[F6] controls whether the path through the

transceiver is set up for receiving or transmitting. Serial data (I2C bus) from

the microcontroller feeds a 16 bit output expander IC405[E8] on the

Rx/Exciter PCB.

104-02907 sheet 1

Output pin 15, which is the transmit/receive select line, connects to cascaded

NAND gates IC7/D[A6] and IC7/C to operate the appropriate mixers via

switching transistors in the receive and transmit modes.

Receive Mode

In the receive mode Pin 15 of IC405 is high (+10 V). This sets output pin 11

of IC7/D low and forward bias transistors V1[B2] and V8[B7]. These supply the

+10 V to switch on the receive mixers IC1 and IC8 respectively.

Transmit Mode

In the transmit mode pin 15 of IC405 is low (0 V). This sets output pin 11

of IC7/D high, switching off the receive mixers. Because pin 11 is connected

to a second NAND gate (pin 9), output pin 10 is now low and forward biases

V2[B4] and V9[B8]. These switches supply the +10 V to switch on the transmit

mixers IC2[D3] and IC9[D7].

Three additional functions of switch V9 in the transmit mode are:

•DC is applied from the collector via D9[C9] and R54 to pin 7 of IC13.

This sets the noise limiter IF amplifier to minimum gain and inhibits the

noise limiter from operating in the transmit mode.

104-02907 sheet 2

•The collector is connected to analogue switch IC305/B[C9] pin 5. With a

high on pin 5 of IC305/B the analogue switch is closed applying a

ground to differential input pin 5 of AGC amplifier IC307/B[C8]. This

sets the AGC to 0 V, switching off the receive 455 kHz IF amplifier

V301/V302[B5], avoiding the necessity to inhibit the demodulator IC302

in transmit mode.

•V9 enables the transmit modulator IC301[D3] by providing a DC bias

current via R312 to pin 5.

104-02908

Serial data from the microcontroller is also applied to IC1[C4] on the PA

assembly. When transmit is selected, a ground on pin 11 energises the

transmit/receive relay K7[D8]. This completes the path from the PA output via

the filters to the antenna socket.

Technical Description 4-4X-2 Technical Service Manual

Publication No: 15-02047

4.2 Receiver

4.2.1 Input Filters

104-02908

The receiver input signal passes through the:

•selected PA low-pass filter

•transmit/receive relay K7

•2 MHz high-pass broadcast filter to the Rx/Exciter & Control PCB.

4.2.2 First Mixer

104-02907 Sheet 1

The receive signal is applied to connector P1[A1] pins 1 and 2 on the

Rx/Exciter & Control PCB. It then passes through a 20 MHz low-pass filter

and transformer T1 to the input pins 12 and 13 of the first mixer IC1[C3].

Mixer IC1 is a combined amplifier/balanced mixer with a gain of

approximately 20 dB. The received signal mixes with the output of Voltage

Controlled Oscillator VCO1 operating between a frequency of 47 MHz and

63 MHz, producing a balanced IF output centred at 45 MHz at pins 3 and

14.

4.2.3 45 MHz Roofing Filter

The 45 MHz IF signal is filtered through a 15 kHz roofing filter consisting of

T3, Z1, L10, Z2 and T4. This removes unwanted products produced by the

mixer. The filter output is applied to the balanced input pins 12 and 13 of

the second mixer IC8[C7] .

4.2.4 Second Mixer

Mixer IC8 is a combined amplifier/balanced mixer and identical to mixer IC1.

The 45 MHz signal mixes with the output of a second Voltage Controlled

Oscillator VCO2[E7] operating between 44.5435 MHz and

44.5455 MHz to produce a second IF centred at 455 kHz.

X-2 Technical Service Manual Technical Description 4-5

Publication No: 15-02047

4.2.5 Noise Limiter

The 455 kHz output at pins 3 and 14 of IC8 is applied via C79, R52, C80,

and R53 to the balanced input of high gain amplifier IC13[C9] pins 4 and 6.

The balanced output at pins 1 and 8, connect to a tuned transformer T6

(455 kHz) which sends its output to the base of the active rectifier V11.

Noise bursts produce positive going pulses at the collector of V11 and

trigger via V12 the monostable flip-flop IC7/A and IC7/B. The pulse width

is determined by C86 and R60 (nominally 250 µs).

The outputs of the flip-flop pins 3 and 4 produce complementary pulses that

are connected to FET gates V14 and V15[D11] and gate out the noise bursts

from the 455 kHz signal.

With V14 on and V15 off, the IF signal passes to the sideband filter.

When a noise burst is present, V14 switches off and V15 switches on,

blocking the IF signal for the period of the gate pulse.

The average DC component of V11 collector current serves as an automatic

gain control to IC13, and flows via R57[C10] to pin 5. This ensures that only

the noise burst signals trigger the monostable. C82 and R56 set the AGC

decay time constant.

4.2.6 455 kHz Filter and IF Amplifier

104-02907 Sheet 2

A 2.5 kHz ceramic filter Z301[B2] receives the IF signal from the noise limiter

and removes the unwanted sideband signal and other unwanted products

generated by the second mixer. The wanted sideband centred at 455 kHz

passes from the filter to a two stage gain controlled amplifier consisting of

V301[B4] and V302 and associated components.

The IF amplifier is broadly tuned to 455 kHz by the tuned circuits

L301/C304 and L302/C308. The output of the IF amplifier (drain of V302)

passes via coupling capacitor C310[B6] to the demodulator IC302 pin 1.

The 455 kHz signal converts to audio when mixed with the local oscillator in

the double balanced mixer IC302. The local oscillator is set to 456.5 kHz for

USB conversion and 453.5 kHz for LSB.

Note: Local oscillators VCO1 and VCO2 shift by a total of 3 kHz when

switching from USB to LSB. This enables filter Z301 to be used

for either sideband.

Technical Description 4-6X-2 Technical Service Manual

Publication No: 15-02047

4.2.7 Automatic Gain Control

To increase the dynamic range of the receiver and to maintain an almost

constant audio output for large variation of input levels, an automatic gain

control (AGC) operates on the two stage 455 kHz IF amplifier.

The demodulated output from pin 6 of IC302 is applied to amplifier

IC303/A[D7] (set to a gain of 3). At its output (pin 1) the audio connects to a

full wave peak rectifier circuit consisting of:

•D305[B8] to rectify the positive component of the audio

•inverter IC307/A and D304 to rectify the negative component of the

audio.

Both diode cathodes are ORed and charge capacitor C330 via R345 to the

peak audio level (less the forward diode drop of D304 and D305).

The DC across C330 is applied to one input of the differential DC amplifier

IC307/B (pin 6). The second input (pin 5) is connected to a reference

voltage of 5.2 V set by divider network R350, D306, R351 and R352.

No Signal Conditions

Under no signal conditions, the DC level at the output of IC307/B is set by

the reference voltage (5.2 V). This is then applied to gate 2 of both FETs

V301 and V302 setting the IF amplifier to maximum gain.

With Signal Conditions

When the receive signal is of sufficient level to cause the peak audio to

charge C330 above the reference of 5.2 V (AGC threshold), the output of

the DC amplifier IC307/B falls. Gate 2 voltage subsequently drops to the

two FETs causing the IF amplifier gain to fall.

The high loop gain of the AGC control network causes any signal above

AGC threshold (about 3 µV EMF) to reduce the IF amplifier gain to a level

required to maintain an almost constant audio output.

The first IF stage (V301) has an additional gain control applied to gate 1.

This consists of V305[C4] and associated resistive components. Under normal

signal levels V301 remains saturated by the forward bias applied from the

AGC line via R369[C4] and gate 1 voltage is determined by the resistor divider

R302 and R303 (1.8 V).

When the receive signal increases to a level that causes the AGC control

voltage to drop to about 2 V, V305 comes out of saturation allowing gate 1

voltage to commence rising. This increases the dynamic gain control of the

first stage and prevents overloading at very high signal levels.

The AGC fast attack time is set by the time constant of R345/C330[C8] and

the slow decay time by R347/C330.

X-2 Technical Service Manual Technical Description 4-7

Publication No: 15-02047

4.2.8 Mute

Squaring Amplifier

The audio at the output of IC303/A[D7] (pin 1) is connected to the input of

IC308/A[E7] which operates a squaring amplifier. The squared output from

pin 2 charges C333 via D307[D8] during the negative excursions and the

charge is transferred to C334[F8] by V304 during the positive excursions. The

resultant DC voltage on C334 is proportional to the frequency of the audio.

Low Pass Filter

IC309/B[E9] and its associated components function as a low-pass filter with a

cut-off frequency of approximately 10 Hz. The output from IC309/B is a

DC voltage varying at the syllabic rate of the received speech.

Window Comparator

IC308/B[E10] and IC308/C form a window comparator where the window

width is adjusted by the mute sensitivity preset R358[E9]. The divider

network R360 and R361, together with C338, averages the output of

IC309/B to provide the reference voltage for the window comparator. If the

output from IC309/B rises above or falls below this reference by the amount

set by R358, then the ORed outputs of IC308/B and IC308/C will discharge

C339 applying a low to the input of comparator IC308/D on pin 10.

The second input at pin 11 of comparator IC308/D is set to 4 V by resistor

dividers R365 and R366. When input pin 10 falls below 4 V, the comparator

output at pin 13 goes high and indicates to the microcontroller IC403, via

input pin 14, that speech has been detected.

Mute detection timing is controlled by discharging C339 through R362 for a

fast attack, and charging of the capacitor via R363 for a slow release (about

3 seconds).

Control

104-02907 Sheet 2 and 3

When mute mode is selected by the mute switch on the front panel, a low is

applied to input pin 29 on the microcontroller (IC403). The microcontroller

sends via the I2C bus to IC405, instructions to latch output pin 21 (mute-

out) low. This applies a low to the IC305/A pin 13, opening the mute gate

and breaking the audio path to the volume control.

When speech is detected by the mute circuit, a high is applied from the

comparator IC308/D pin 13 to the microcontroller (IC403) pin 14. The

microcontroller, via the I2C bus, sets pin 21 of IC405 high. This closes the

mute gate IC305/A and passes the received audio on to the volume control.

Technical Description 4-8X-2 Technical Service Manual

Publication No: 15-02047

4.2.9 Volume Control and Audio Amplifier

The audio from the output of the mute gate passes through a ribbon cable to

the volume control on the front panel.

The output of the volume control is passed to the loudspeaker amplifier IC2.

The audio amplifier can supply 8 W into a 2 ohm load and supplies

approximately 2 W to the internally fitted 8 Ω speaker.

4.3 Transmitter Exciter

4.3.1 Microphone Compressor

The microphone is connected via connector P100 on the front panel to an RF

filter network R6 and C9 and then by ribbon cable to the main PCB (P401

pins 26 and 19). From here, the microphone speech passes to the input

network of the microphone compressor amplifier.

104-02907 Sheet 2

The input network includes an analogue switch IC305/D[H2], to disable the

microphone when other transmit functions are selected.

The microphone compressor amplifier, consisting of IC303/B[F3], IC306/A[H3]

and IC306B[G3], V303[G3] and associated components, provides a constant

output level for a large variation in speech levels applied to the input.

With no speech present, amplifier IC303/B is set to maximum gain

determined by feedback resistor R337 and shunt FET V303, functioning as a

variable resistor and set to minimum resistance (≈150 Ω).

The output of the amplifier IC303/B is connected to the inputs of IC306/A

and IC306/B which form a window comparator. The window is set by the

divider chain R330 to R342 to ± 0.25 V centred at 5 V.

When the level of speech applied to the microphone amplifier results in the

output exceeding 0.25 V peak, the window comparators produce negative

going output pulses lowering the DC charge on capacitor C238.

This effect reduces the voltage on the FET gate IC303, increases the

effective resistance of the FET (IC303) and lowers the gain of the

microphone amplifier.

The microphone amplifier is now in compression and the output level

remains constant for any further increase in speech level.

The microphone amplifier has a compression range of approximately 30 dB.

X-2 Technical Service Manual Technical Description 4-9

Publication No: 15-02047

4.3.2 Modulator

The microphone output is capacitor-coupled by C314[D4] to the input of the

balanced modulator IC301[D3]. The modulator is enabled when DC is applied

to the bias input pin 5 via R312 and transistor switch V9 (sheet 1[B8]).

The audio mixes with the local oscillator of 456.5 kHz (453.5 kHz for LSB)

applied to pins 8 and 10, to produce a DSB output at pin 6 that passes via

D301[C3] to the 455 kHz sideband ceramic filter Z301.

4.3.3 455 kHz Filter and First Mixer

104-02907 Sheet 1

Filter Z301 passes only the wanted sideband, via tuned transformer T5[D9], to

the input pins 12 and 13 of the first balanced amplifier/mixer IC9[D7]. The

mixer is enabled by operating transistor switch V9[B8] and applying DC via

R35 to the VCC input pin 4 and bias current via R38 to pin 11.

The 455 kHz transmit signal is filtered with the local oscillator VCO2 and

applied to pin 5 to produce a second IF output signal centred on 45 MHz at

pins 3 and 14. The mixer/amplifier has a gain of approximately 20 dB.

4.3.4 45 MHz Roofing Filter

The 45 MHz IF signal is filtered through a 15 kHz roofing filter consisting of

T4, Z2, L10, Z1 and T3[C5]. This removes unwanted products of the first

mixer. The filter output is applied to the balanced input of the second mixer

IC2[D3] at pins 12 and 13.

4.3.5 Second Mixer and Exciter Output Filter

The second mixer IC2 is enabled by transistor switch V2[B4], applying DC via

R7 to the VCC input pin 4 and bias current via R8 to pin 11.

The 45 MHz transmit signal mixes with local oscillator VCO1 and is applied

to pin 5, producing the selected channel frequency at the mixer output pins 3

and 14. The mixer/amplifier produces approximately 20 dB gain.

The mixer output is fed via a 20 MHz low pass filter to the transmit exciter

output connector P1 pin 1 and 2. From here it couples via coaxial cable to

the PA assembly.

Technical Description 4-10 X-2 Technical Service Manual

Publication No: 15-02047

4.4 Local Oscillators

4.4.1 Introduction

104-02907 Sheet 1

Two digitally controlled synthesized local oscillators drive the first and

second mixers. VCO1 operates between 47 MHz and 63 MHz, moving in

2 kHz steps. VC02 operates between 44.5435 MHz and 44.5455 MHz,

moving in 10 Hz steps.

The synthesizers are each programmed in serial data format from the

microcontroller which accesses channel data stored in memory.

Each synthesizer is locked to the reference oscillator. This consists of a

7.304 MHz crystal oscillator held at a constant temperature of 60°C by a

PTC thermistor oven.

4.4.2 VCO1 and PLL

VCO1[E3] is designed around a differential amplifier consisting of FETs V3

and V4. The frequency of oscillation is determined by the tuned circuit L7,

C23 and the capacitance of the varicaps D1 to D4. Oscillator output power

is set by R14 and R15. Resistor R12 compensates the output level over the

frequency range.

Capacitor divider C29 and C30 couple the oscillator output to the buffer

amplifier V5, where the output drives the two mixers IC1 and IC2 and the

prescaler IC4. In each case pin 5 is used as the input.

The high frequency output from VCO1 is divided by 64/65 prescaler IC4[E5]

down to a frequency range of 734 kHz to 984 kHz at pins 2 and 3. A high

or low on pin 4 sets the division ratio.

IC5 is a complex PLL chip that contains two programmable dividers and a

phase comparator. The phase comparator compares two input signals of the

same frequency and outputs a voltage which is dependant on their relative

phase.

One input to the comparator IC5 on pin 4 is from the prescaler IC4. This is

divided to 2 kHz by one of the programmable dividers. Quartz crystal Z3

connected between pins 7 and 8 forms the reference oscillator set to a

frequency of 7304 kHz. The reference oscillator is divided down to 2 kHz

by the second fixed programmable divider.

The two divided signals are applied to the phase comparator and when the

two signals are 'locked' in phase the comparator output is at mid-rail

(2.5 V). As these two frequencies are locked together by the action of the

loop, changing either programmable divider will change the VCO frequency.

X-2 Technical Service Manual Technical Description 4-11

Publication No: 15-02047

Two separate outputs are available from the phase detector. PDB (pin 2 of

IC5) is a coarse control that outputs a mark to space ratio proportional to

the difference frequency between the divided signals. PDA (pin 1 of IC5) is

the fine control and gives an analogue output that takes over from PDB

when the two signals are close to phase lock.

Transistors V6, V7[C3] with C38, R23, R26, and R27 form the loop filter.

The input at the base of V6 is biased to 2.5 V by H1. The output DC can

swing between ground and the positive rail and is used to control the

varicaps and consequently the frequency of the VCO.

When a new channel is selected, the microcontroller changes the value of the

programmable counter fed by the prescaler IC4. Because the two signals

driving the phase detector are now no longer at the same frequency, the

phase detector outputs pulses to the loop filter where the output ramps in the

direction necessary to establish lock.

4.4.3 VCO2 and PLL

104-02907 Sheet 1

VCO2[E7] is a crystal controlled Colpitts oscillator. The tuned circuit

consisting of L15, C65 and C66 sets the appropriate frequency of operation.

The network consisting of C63, Z4, D8 and L17 is equivalent to a voltage

controlled, very high Q series tuned circuit. This network effectively

grounds the gate of V9 at the series resonant frequency and determines the

frequency of oscillation.

The drive to mixers IC8 and IC9 and the prescaler IC10 is via the capacitor

divider C66 and C67, using pin 5 of each IC.

The phase locked loop incorporating VCO2 works in a very similar manner

to PLL1. The main differences are:

•only one phase detector output is used to drive the loop amplifier

IC11[G7] pin 17

•the phase comparator varies from 1.1 kHz to 2.0 kHz.

Allowing the phase detector frequency to vary enables this loop to move in

10 Hz steps while having a high phase detector frequency.

The 7304 kHz reference oscillator output from pin 8 of IC5 is applied to pin

2 of PLL IC11.

The DC output at pin 1 of loop filter IC12/A[H7], is applied to the varicap

D8[E6] and controls the frequency of the VCO.

Technical Description 4-12 X-2 Technical Service Manual

Publication No: 15-02047

4.4.4 455 kHz Local Oscillator

USB

For upper sideband the modulator/demodulator local oscillator is derived

from the 7304 kHz reference oscillator divided by 16 (456.5 kHz).

The 7304 kHz reference oscillator (USB) is taken from the oscillator output

pin 3 of IC11 and applied to the input of a ÷ 2 divider IC16A[H8] at pin 3.

The output pin 6 is applied to a second ÷ 2 divider IC16B pin 11 and the

clock input of the microcontroller IC403 pin 16.

In USB mode, the second divider IC16B is enabled by the microcontroller

selecting the enable line pin 10 high, at the same time disabling the 1814 kHz

oscillator IC14/C pin 8.

The 7304 kHz ÷ 4 reference signal at pin 8 of IC16/B is fed via OR gate

IC14/B to two cascaded ÷ 2 dividers IC15/A and IC15/B. This produces a

balanced output at pins 8 and 9 at a frequency of 456.5 kHz. From here it is

applied to the balanced local oscillator input of modulator IC301 (sheet 2)

and demodulator IC302 pins 8 and 10.

LSB

For lower sideband a separate 1814 kHz crystal oscillator divided by 4 is

used. In LSB mode, the output from divider IC16/B is disabled by the

microcontroller at the same time enabling IC14/C[F9], the 1814 kHz crystal

oscillator.

The output from pin 10 of the oscillator is fed via OR gate IC14/B and

dividers IC15A and IC15B to the modulator and demodulator for the local

oscillator frequency of 453.5 kHz.

4.4.5 Clarifier

Operation of the clarifier on the front panel produces a code which is

converted to serial data and read by the microcontroller. For each clarifier

step detected, the microcontroller reprogrammes IC11, shifting VCO2 in

10 Hz steps from the nominal frequency. The clarifier range is ± 50 Hz for

channels 2 MHz to 5 MHz and ± 10 ppm above 5 MHz. For example, the

clarifier range at 18 MHz is ± 180 Hz.

The operation of the clarifier control varies the frequency of VCO2 in 10 Hz

steps. This is done by varying both VCO2 and the reference frequency

dividers according to a 'look-up' table in the transceiver's operating system.

The phase comparison frequency varies from 1.1 to 2.0 kHz.

An audible indication is given when the clarifier reaches its upper or lower

limit. The clarifier automatically resets to mid frequency when the channel is

changed.

X-2 Technical Service Manual Technical Description 4-13

Publication No: 15-02047

4.5 Micro and Peripherals

4.5.1 Microcontroller

The microcontroller monitors all input lines and outputs commands to

various parts of the transceiver according to the information received and the

program stored in the ROM.

The microcontroller IC403 is a member of Motorola's MC68HC05 family.

The 8-bit microcontroller contains CPU, RAM, ROM, A/D, Pulse Length

Modulated Outputs, I/O, serial Communications interface, Timer system and

Watchdog.

4.5.2 I2C Bus

The serial data ports of the microcontroller IC403 pins 42 (data) and 44

(clock) provide the I2C bus to communicate to the following peripherals:

IC405 - I2C Bus/16 bit output driver

Commands from the microcontroller via the I2C bus, select the outputs of

IC405 to control PTT, USB/LSB, TUNE, MUTE, AGC CLAMP, BCD lines

for antenna control, UNLOCK 1 and 2 Leds, MIC enable and TX tones

enable.

IC404 - EEprom

A non-volatile memory device that provides the microcontroller with the

programmed channel information.

IC1-I2C bus/8 bit input

Provides the microcontroller with the front panel channel and clarifier control

functions.

IC5 and IC11

The PLL integrated circuits which control VCO1 and VCO2.

4.5.3 PA Control Bus

A separate serial data bus is provided from the microcontroller (pins 37 and

38) to control an 8 bit driver IC1 on the PA PCB. This enables the

microcontroller to select:

•the PA filters

•Antenna 1 or 2

•and the Tx/Rx changeover relay.

Technical Description 4-14 X-2 Technical Service Manual

Publication No: 15-02047

4.5.4 Front Panel Controls

104-02909

The front panel has the following controls:

Channel Change

A continuous rotatable 12 position switch provides a Gray code on its four

outputs and is connected to IC1 pins 9 to 12. Channel selections are read by

the microcontroller via the I2C bus. The microcontroller sets up VCO1 and

VCO2 according to the information stored in the EEPROM. Only 10 of the

12 positions are used.

Clarifier

A continuous rotatable 12 position switch provides a Gray code on its four

outputs and is connected to IC1 pins 4 to 7. Any position change in the

receive mode is read by the microcontroller via the I2C bus.

The microcontroller adjusts VCO2 in 10 Hz steps to a limit depending on the

channel frequency. The clarifier automatically resets to mid frequency when

the channel is changed.

Emergency Call

A biased toggle switch provides a ground to pin 28 of microcontroller

IC403. If enabled on the selected channel, the microcontroller selects the

PTT function and outputs the two emergency tones of 880 Hz and 1320 Hz

from pins 1 and 2. Modulator IC301 receives these signals via the

microphone amplifier.

USB/LSB

A two position toggle switch provides the selection of USB or LSB by a

high or low applied to pin 30 of microcontroller IC403. The microcontroller

selects the appropriate local oscillator (applied to the

modulator/demodulator).

The selection of USB and LSB is only available when enabled for the channel

selected.

Tune/Mute Off/Mute On

A three position toggle switch, biased up for Tune select and selectable for

Mute On/Mute Off.

When Tune is selected, a ground is applied to pin 32 of microcontroller

IC403. This selects transmit mode and injects the carrier via IC14/A and

V13 into the transmit path of the exciter.

When Mute On is selected, a ground is applied to pin 29 of microcontroller

IC403. The microcontroller changes mute control line from IC308/D pin 13

to operate the mute gate IC305/A.

Power On

The power on switch is part of the volume control assembly. When the

contacts are closed, relay K8 is energised on the PA PCB and provides the

DC supply to the transceiver via contacts K8-1.

X-2 Technical Service Manual Technical Description 4-15

Publication No: 15-02047

Volume

The volume control adjusts the audio level between the post mute output

(IC305/A) and the speaker audio amplifier IC2 mounted on the front panel

PCB.

4.5.5 Tune

104-02907 Sheet 1

When the tune function is enabled, a ground is applied to pin 32 of

microcontroller IC403 [104-02907 Sheet 3] from the Tune switch. The

microcontroller detects the ground and sets the output of IC405 pin 20 low

via the I2C bus while applying a low on pin 15 thereby selecting transmit

mode (PTT).

The output from pin 20 of IC405 is connected to pin 2 of NOR gate IC14/A

[104-02907 Sheet 1]. When low, the 456.5 kHz carrier (453.5 kHz for LSB)

connected to pin 3 of IC14/A, appears at the NOR gate output pin 1. This

applies the carrier via the driver transistor V13 to the input of the first Tx

mixer IC9.

The low from pin 20 of IC405 also connects to pin 11 of NOR gate IC14/D.

This sets the output of IC14/D high and biases V12 into saturation. The

output of the second cascaded NAND gate IC7/B pin 4 goes low opening

FET gate V14. This stops the carrier being loaded by the sideband filter

Z301.

4.5.6 Tone Generation

The tones are generated by the microcontroller IC403. Outputs from pins 1

and 2 (TCMP2 and TCMP1) are filtered by resistor/capacitor network R245

to R249 and C412 to C414, and provide the audible signals required for

Emergency Call, alarm and warning tones.

4.5.7 A/D Inputs

104-02907 Sheet 3

The microcontroller monitors supply volts and the VSWR signals applied to

its A/D inputs as follows:

Supply voltage

The A line supply volts is applied via resistor divider R410[F4] and R413 to

pin 3 of IC403. The microcontroller provides high alarm tone and disables

the transceiver when the supply volts rises above 16.5 V. A low tone occurs

when the supply drops below 10.5 V without disabling the transceiver.

Transmit forward power

The transmit forward power detector output from D1[B2] (FWD-PWR) on the

PA assembly is applied via resistor divider R409[F3] and R412 to pin 12 of

IC403.

Technical Description 4-16 X-2 Technical Service Manual

Publication No: 15-02047

Transmit reflected power

The transmit reflected power detector output from D2 (REF-PWR), on the

PA assembly, is applied via resistor divider R411 and R413 to pin 3 of

IC403.

Tune Pass/Fail

The microcontroller compares the forward and reflected power when in the

tune mode and provides a pass or fail indication on completion of the tune

cycle. A pass tone indicates a VSWR of < 3:1 and a fail tone indicates a

VSWR of > 3:1.

4.5.8 Microcontroller Reset

104-02907 Sheet 3

The reset line to the microcontroller IC403 pin 18 is normally held to 5 V.

Reset circuit IC304/B[G4] and its associated components monitor the supply

voltage on A line. When the supply falls below 8.7 V, the output of IC304/B

applies a low via D403 to the reset pin 18.

To eliminate jitter on the reset line, resistor R417 provides a hysteresis to the

reset network. This prevents the output of IC403 from going high until the

supply has risen above 9 V.

4.6 PA and Filters

104-02908

Power Supply

The drivers and output stages (including part of the output bias circuit) are

permanently connected to the supply voltage when the Power On relay K8 is

energised. Power to the rest of the PA is switched by V2[D9] when PTT is

enabled.

Filter Selection

The selection of the PA filters and the operation of the PTT are controlled by

the microcontroller. Serial data from the microcontroller IC403 is applied to

IC1[C4] (serial data input/8 bit output driver).

Depending on the channel frequency, the microcontroller selects the

appropriate filter by grounding one of the output pins 14 to 18. In addition,

pin 11 will be grounded or set high depending on whether antenna 1 or 2 is

required (J1 or J2).

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When PTT is selected, the microcontroller sends serial data to IC1 to select

pin 12 to ground. This energises the transmit/receive changeover relay K7

and forward biases DC switch V1[D3] providing DC to the input and predriver

stages. The control circuit to the output bias circuit is enabled and the input

DC is supplied to the +5 volt regulator IC2.

4.6.1 Gain Control Stage

104-02908

The RF input from the Exciter is terminated by R10[G2] and drives the

common base long tail pair V8[F6] and V9 through R29 and R34 in parallel

for signal currents. R30 sets the DC condition of the long tail pair and is RF

bypassed by C77[G6].

The gain of V9 is controlled by the ratio of emitter DC currents in V8 and

V9. The RF input is split between the emitters of V8 and V9 inversely

proportional to their input impedance. The gain of V9 reduces when the

ALC increases the current in V8. The collector load of V9, consists of L19

and R33 which are frequency compensating components to reduce low

frequency gain.

4.6.2 Predriver Stages

The collector output of V9 is coupled, via C76, to emitter follower V10

where the output drives the transformer feedback predriver stage V11. High

frequency peaking in the emitter circuit is provided by L20 and C79.

4.6.3 Driver Stage

The push-pull class B driver stage, V13 and V14, is voltage driven from the

secondary of T2[E8]. The transformer output of T3[E10] provides the current

drive to the output stage and R49, L24 and C85 provide the low impedance

source required below 3 MHz.

Bias for the driver stage is provided by the total current of the emitter

follower and predriver stages passing through transistor V12 connected as a

diode. The bias is set by SOT resistor R39 and changes the voltage across

the collector-emitter of V12[G8].

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4.6.4 Output Stage and Bias Regulator

The push-pull class B output stage V18[E11] and V19 is base driven from the

centre tapped secondary winding of transformer T3. The centre tap provides

the bias feed from the bias regulator.

The bias regulator V16 and V17 provides a constant voltage to the bases of

V18 and V19. Transistors V16 and V17 form a feedback voltage regulator,

the output voltage being the base-emitter voltage of V16, adjustable by

preset potentiometer R45. Zener diode V15 and resistor R47 cause the bias

to increase when the supply voltage drops below 11 V to reduce

intermodulation distortion.

Transistor V16 is mounted on the PA heatsink and provides temperature

compensation to the bias network.

The balanced to unbalanced impedance matching output transformer couples

the power amplifier output via the transmit/receive relay K7 to the band

filters.

4.6.5 Output Filters and Antenna 1 and 2 Select

The frequency range of 2 MHz to 18 Mhz uses five low pass filters selected

by relays K2 to K6 and operated by IC1. The filters are selected to remove

harmonics generated by the PA.

The output of the filter circuit passes through the Automatic Level Control

(ALC) RF bridge to antenna output J1 or J2 as selected by relay K1.

4.6.6 ALC Control

104-02908

Automatic Level Control is provided from the following sources:

•Forward power

•Reflected power

•Output stage collector swing

•Battery voltage

•Heatsink over-temperature.

Control Inputs

The ALC control inputs are applied to V4 - V7 and the ORed output is

connected via R20 to positive input (pin 5) of the ALC level comparator

IC3/B[F5]. The negative input (pin 6) is set to 3.6 V by the divider R22, R23,

and R24.

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PA Gain Control

In the absence of any ALC inputs, the output of IC3/B holds the base of V8

to 3.6 V. With V9 base referenced to 5 V, V8 cuts off setting V9 to

maximum gain. An ALC control signal that causes any of the transistors V4

to V7 to conduct, results in the output of IC3/B rising to reduce the gain of

V9, and therefore controls the gain of the PA.

The output voltage of the RF bridge T1, L1, R1, R2 and capacitor divider

C3, C4, C5 and C6 is rectified by D1 for the forward power and D2 for the

reflected power. The addition of L2 (Link X not fitted) allows for a

reduction in output power at the frequencies above 12 MHz.

The output of the forward rectifier D1 is applied via divider R12 and R13 to

R15 to input of V4 and determines the PEP power output level (set by SOT

R14). D1 is also connected via R17 to input V5 and in conjunction with C68

sets the average power level to approximately 60 W.

The output of the reflected rectifier D2 is applied via divider R18 and R19 to

input V6 and takes control of the ALC when the reflected power exceeds 10

watts ( > 2 : 1 VSWR ).

Peak output collector swing is monitored by R57[G11], D8 for V18 and R54,

D7 for V19. The diode cathodes are ORed and applied to V7[F4] via divider

R55 and R56. Transistor V7 conducts and limits the collector peak to 42 V

to prevent damage to the output transistors.

Battery Voltage

The battery voltage is monitored by V3. When the supply volts (A line)

drops to about 12 V the voltage at the base of V3, set by the resistor divider

R8 and R9, falls to 4.3 V causing V3 to conduct. This causes a rise in

voltage across R15 (part of resistor chain) and changes the threshold of the

forward ALC detector, reducing the output power. As the control is linear,

further reduction in supply volts continues to lower the output power.

Heatsink

When the heatsink exceeds 80°C, PTC resistor R22 rapidly increases in

value, reducing the ALC threshold level to comparator IC3/B. This lowers

the output power and prevents the heatsink from exceeding 90°C.

Technical Description 4-20 X-2 Technical Service Manual

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X-2 Technical Service Manual 5-1

Publication No: 15-02047

5Maintenance

5.1 Introduction

This chapter provides maintenance and fault finding procedures that can be

carried out on the X-2 transceiver. It covers general warnings and cautions

to be observed when working with electronic equipment. It outlines fault

finding steps when receive, transmit failures occur and provides removal and

installation procedures. A section on unlocked synthesizers has been

provided should VCO1 or VCO2 lose lock.

5.2 General

5.2.1 CMOS Devices

Complementary Metal Oxide Semiconductor (CMOS) devices in the

Transceiver have built-in protection. However, their extremely high open-

circuit impedance makes them susceptible to damage from static charges.

Care must therefore be used when shipping and handling the devices and

servicing equipment in which they are installed. The following precautions

should be observed:

Packaging

Replacement CMOS devices are supplied in special conductive packaging.

They should remain in this packaging until required for use.

Switch off

Ensure that power supplies are switched off before making connections or

disconnections between circuit boards.

Handling

Handling of circuit boards and particularly touching any conductive parts

should be kept to a minimum.

Grounding

Anything connected to or touching the circuit board tracks should be

grounded. Observe the following:

•Test equipment connected to a board should be grounded through its

mains lead.

•Static charges that may build up on a person can be discharged by

touching a grounded metal surface with both hands. This should be

done before, and at frequent intervals during work on circuit boards.

•Wearing a suitably grounded conductive wrist strap will minimise the

static build-up on the person.

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5.2.2 Circuit Boards

When servicing printed circuit boards the following should be observed:

Excessive heat

Excessive heat may lift the track from circuit boards, causing serious

damage. Avoid the use of high powered soldering irons. A 60W maximum

iron, preferably temperature controlled at approximately 370°C, is sufficient

for most tasks. A slightly higher temperature (425°C) iron may be required

for heavier components such as PA transistors. Apply the iron only long

enough to unsolder an existing joint or to solder a new one.

Unsoldering

When unsoldering use a solder-sucker or Solderwick to remove solder.

ICAUTION

Do not use sharp metal tools such as screwdrivers or twist drills as these

will damage the printed circuit track.

Component substitution

Avoid unnecessary component substitution as this may damage the

component, the circuit track or adjacent components.

Component replacement

When a component is diagnosed as defective, or the fault cannot be

diagnosed in any other way than by substitution, observe the following when

installing replacement:

•Axial leads - Components with axial leads, such as resistors and tubular

capacitors, can often be replaced without unsoldering the joints on the

boards. The defective component can be removed by clipping its leads

close to the component leaving the leads soldered to the board. These

leads should be straightened so that the leads of the replacement can be

wrapped around them and soldered. After soldering, the excess lead

should be clipped off.

•Remove solder - When a component has been unsoldered from the

board ensure the holes are clear of solder before inserting the leads of

the replacement.

ICAUTION

Never force the leads through the holes as this will damage the circuit track,

particularly where plated through holes are used.

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•Observe orientation - Before replacing defective diodes, transistors,

electrolytic capacitors or integrated circuits, observe any marking

indicating polarity or orientation. It is essential that these types of

components are installed with the correct connections. Consult the

manufacturer's data for indications of the polarity of diodes or capacitors

and transistors.

•Heat sinking - When soldering to the board, use long-nosed pliers or

another form of heat sinking on the leads of heat sensitive components.

•Thermal conduction - When replacing transistors that are mounted on

heat sinks, ensure good thermal conduction between the heat sink and

the replacement. This can be done by cleaning the mounting surfaces and

recoating them with a thermal conduction compound such as Jermyn

Thermaflow A30.

Track repair

Broken or burned sections of printed circuit track can be repaired by bridging

the damaged section with tinned copper wire. The section where the repair

is to be made must be cleaned, observing the precautions outlined above

before soldering.

Integrated circuit replacement

It is often possible to desolder and remove components from the board

without damage to the component or the tracks on the board. However,

integrated circuits with many connections, mounted on double-sided circuit

boards with plated-through holes are almost impossible to remove intact and

the operation is likely to damage the circuit boards. To replace these

components their leads must be cut individually until the body of the

component can be removed. Individual leads must be unsoldered and

removed. Excess solder must be removed before inserting the replacement

component. Refer to the bullet section "Remove solder" before inserting

replacement components.

5.2.3 Transmitter Precautions

When taking measurements of the low level stages of the exciter it is

advisable to remove the drive to the PA and Filter PCB. The supply voltage

is applied to the PA when the transceiver is switched on. Due care should be

exercised when connecting probes.

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5.2.4 Probe Precautions

The following should be observed when connecting CRO probes to the

Transceiver:

1. When connecting probes to the PA assembly, the earth clip lead should

be wound around the body of the probe so that the earth clip just

reaches the probe tip. This reduces stray RF pick-up.

2. The earth clip should be connected to the ground plane adjacent to the

point of measurement to which the probe tip is connected.

3. It is not advisable to connect two probes at the same time, particularly

when one is earthed to the PA ground plane and the other is earthed to

the chassis. This may cause earth loop problems.

4. Probes should be connected after power has been applied to the

transceiver and the test equipment. The earth connection should be

made first and disconnected last.

5.3 Fault Diagnosis

5.3.1 General

The removal and replacement of components may damage the components

and/or the printed circuit boards. In some cases it is impossible to remove

components without destroying them. It is important therefore to carry out

as much diagnosis as possible with components in situ. Specific tests are

described later in this section. The following general points should also be of

assistance:

Spare boards

If spare boards are held in stock, they may be substituted to localise the fault

to one board.

Transistor tests (static)

Transistor failures are most often due to open-circuit base-emitter or base-

collector junctions, or a short circuit between emitter and collector.

These types of faults can often be detected without removing the transistor,

using the ohms range of an analogue multimeter or diode test on a digital

multimeter. The two junctions should both give the appearance of a diode, i.e

high resistance with the multimeter leads one way round and low resistance

when the leads are reversed. (Polarity depends on whether a PNP or NPN

transistor is being tested). Resistance between collector and emitter should

be high with the multimeter leads either way round. The circuit diagram

should be examined for parallel paths before a transistor failing these tests is

removed.

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Transistor tests (dynamic)

Some transistor faults can be diagnosed by measuring voltages within the

circuit. One of the most significant voltage measurements is the base-emitter

voltage. The polarity of this will depend on the type of the transistor (PNP or

NPN). A base emitter voltage between 0.6 and 0.8 V should be measured on

a forward-biased base-emitter junction (double this voltage for a darlington

transistor).

With its base-emitter junction forward biased the transistor should conduct.

Some indication of satisfactory operation of the transistor can be obtained by

measuring the voltage drop across its collector or emitter resistor and short

circuiting its base to the emitter. The short circuit removes the forward bias

cutting off the transistor, so that the voltage across the resistor is reduced

considerably.

Integrated circuits

Before replacing an integrated circuit which has no output, make sure the

fault is due to the IC or its load. As a general rule, if changes in input cause

absolutely no changes in the corresponding output the IC should be

suspected. If, however, even a very small change in output can be detected

the load is more likely to be the cause. Depending upon the circuit further

tests should be made by disconnecting resistors, capacitors, etc to verify this

diagnosis before removing the IC.

Reading the Technical description and understanding how the Transceiver

functions, will assist in diagnosing any possible faults that may occur.

5.3.2 Voltage measurements

The circuit diagrams and relevant circuit notes give voltages at various points

under the various conditions to enable the faulty section of the Transceiver to

be located. The parameters listed below should always be checked first:

The supply voltages used on the Rx/Exciter & Control PCB are:

'A' rail unregulated supply 13.6 V nominal.

'B' rail regulated supply (IC401) +10 V ± 0.2 V.

+5VA regulated supply (IC3) +5 V ± 0.4 V.

+5VB regulated supply (IC402) +5 V ± 0.4 V.

TP6 switched supply (IC7/C), B rail voltage in receive, 0 V in transmit.

TP7 switched supply (IC7/D), B rail voltage in transmit, 0 V in receive.

The supply voltages used on the PA PCB are:

'A' rail unregulated supply 13.6 V nominal.

+5V regulated supply selected in transmit only (IC2) +5 V ± 0.4 V.

Zener controlled supply to IC1 (V1) +5 V ± 0.25 V.

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5.3.3 No Reception

104-02907 sheet 1

For a receive failure:

1. Check the microphone plug is fitted. The link in the plug completes the

audio path to the internal loudspeaker.

2. Check the Mute gate is operating and closed.

3. Check the supply voltages are correct as detailed in Section 5.3.2

4. Using a Signal Generator and a series capacitor (about 100 nF) apply a

signal to the test points shown on the circuit diagrams. The receive

levels and frequencies, shown on the RF and IF circuit diagrams,

should cause the AGC to fall by about 0.5 V from its no signal level of

approximately 5.2 V (under no fault conditions).

5. Start at the 455 kHz IF amplifier and proceed back through the

receive path towards the antenna. When the injected signal is no longer

heard or the AGC no longer falls by 0.5 V under application of levels

shown on the circuit diagram, a close examination of the satisfactory

and failed check points should indicate where the fault lies.

6. In the case of an audio fault, apply a signal from the Signal Generator

to the receiver input at a frequency set to approximately 1 kHz above

the channel frequency (1 kHz below for LSB). With the aid of an

oscilloscope, trace the audio signal path from the demodulator output

to the loudspeaker.

Note: If the AGC is operating satisfactorily then audio signal should

be present at the output of pre-amplifier IC303/A, as this point

also feeds the AGC detector circuit.

7. If the receive fault shows as an oscillation or instability, check that

neither of the transmit mixers, IC2[D3] and IC9, have DC on pin 4 or 11

( < 0.5 V). Check the modulator has no DC at pin 5. If DC is measured

at any of the points indicated, check the following:

•Check the base/emitter voltage to switching transistors V2[B4] and

V9. If it measures 0.5 V or more, check NAND gates IC7/C[A6]

and IC7/D output voltages are correct as shown on the circuit

diagram.

•If DC is measured on pin 4 and 11 of mixer IC2, unsolder and lift

one side of resistor R7[C4]. If the voltage still appears at the

collector of V2, suspect collector/emitter leakage of transistor and

replace. If the voltage still remains on pins 4 and 11 of the mixer,

replace IC2.

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•If DC is measured on pin 4 and 11 of mixer IC9, unsolder and lift

one side of resistor R35[C8]. Check if the DC is still on the mixer

pins, replace IC2.

If the voltage is only on the collector of V9 and R35 is lifted,

apply a short circuit between pin 5 of IC301[D3] and ground

[04-02907 sheet 2]. If the voltage goes from the collector of V9,

replace modulator IC301. If the voltage remains on the collector

with pin 5 shorted, replace V9 (collector/emitter leakage).

5.3.4 Transmitter Failure

For a transmit fault proceed as follows:

1. Check the supply voltages are correct as detailed in Section 5.3.2.

2. Apply an audio signal of about 1 kHz at a level of 10 mV RMS to the

microphone input. Select transmit mode (PTT) and with the aid of an

oscilloscope trace the audio, IF and RF signals through the transmit

path. Check the measured levels correspond approximately to the

levels shown on the circuit diagrams. A reduction of signal or complete

failure at any of the check points should indicate the approximate

location of the fault.

5.3.5 Unlocked Synthesizer

104-02907 sheet 1

Loss of lock on VCO1 or VCO2 is indicated by:

•a warning tone in the loudspeaker

•illumination of H1 and/or H2 on the Rx/Exciter & Control PCB.

Should the above warnings occur, proceed as follows:

1. Check the 18 V supply is present and connected to:

•oscillator VCO1[E2] (V3 and V4)

•control amplifier V6[G3] and V7.

If VCO2 has failed, check it is present at the control amplifier

IC12/A[H7].

2. Check VCO1 and VCO2 are oscillating. Check that the outputs at

TP4[E4] (VCO1) and TP1[A2] (VCO2) are approximately the level shown

on the circuit diagram. Frequency should be within the range indicated.

3. Check the output levels at pin 3 of the prescalers IC4[E5] and IC10[F7].

Check the frequency is approximately the VCO frequency divided by

64.

4. Check the VCO control voltages on TP3[G1] and TP13[F6] are within the

limits indicated on the circuit diagram.

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5. Check, whilst changing channels, the Enable, Data and Clock pulses

are present at input of synthesizer integrated circuits IC5[F5] at pins 12,

10 and 11 and IC11[G7] at pins 13, 12 and 11.

6. If only VCO2 is unlocked and the previous checks appear correct,

incorrect alignment may be the cause of failure. Re-set VCO2 as

detailed in the VCO2 Adjust Section 7.6.3.

5.3.6 PA Failure

To optimise the amplifier performance, the PA output transistors are

matched in pairs by a coloured dot or letter code. Measurements in this area

depend upon the matched pair of transistors fitted and the frequency of

transmission.

Table 5.1 provides a guide to the peak to peak voltages expected at the

specified points in the PA circuit. They are given for full power output when

driven with a two-tone input. For these tests the supply voltage should be

13.6 V and the output terminated into 50 Ω.

Frequency Battery V10

(Vpp)

V11

(Vpp)

V13/V14

(Vpp)

V18/V19

(Vpp)

(MHz) (Amps) ECECBCB

2.5 9.5 0.20 0.40 0.20 1.10 0.20 20 2.2

3.5 9.5 0.20 0.45 0.25 1.10 0.20 20 2.3

5.5 9.5 0.25 0.45 0.25 1.10 0.20 25 2.7

8.5 10.0 0.35 0.60 0.40 1.20 0.27 28 3.2

15.5 90.55 1.30 0.60 1.00 0.70 35 4.0

17.9 10.0 0.60 1.50 0.60 1.10 0.80 20 4.5

Table 5.1: Peak to Peak Voltages

5.4 Dismantling and Assembling

5.4.1. General

It may be necessary to remove printed circuit boards from the transceiver in

order to carry out certain repairs. The following paragraphs give instructions

on the removal and installation of the boards. While carrying out these

procedures the following general points should be observed:

Screwdriver

Screws with Pozidrive heads are used in almost all locations. Ensure that the

appropriate screwdriver of the correct size is used.

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Connectors

The ribbon cable header and multiway connectors used in locations can be

incorrectly mated with their corresponding connectors. Care must therefore

be taken when installing to ensure these connectors are correctly mated.

Removal of the screws securing the driver transistors V13[E9] and V14 and

bias transistor V17[G10] on the PA assembly requires a 1/16 inch Allen key.

5.4.2 Top and Bottom Covers

To gain access to the printed circuit boards, the top or bottom cover must be

removed from the transceiver. To remove either cover, the four screws (two

on each side) must be removed and the cover lifted.

To replace the cover, place the cover onto the transceiver and refit the

retaining screws.

5.4.3 Rx/Exciter & Control PCB

To remove the Rx/Exciter & Control PCB, disconnect the two ribbon cable

connectors P3 and P401 and the Tx/Rx coaxial connector P1. Remove the

five retaining screws and withdraw the PCB. Reverse the procedure to

install, ensuring the ribbon connectors are aligned correctly.

5.4.4 Front Panel PCB

To gain access to the front panel PCB, remove the front panel from the

frame of the Transceiver by removing the two retaining screws located on

each side of the front surround. Disconnect the 26 way ribbon connector

P401 from the Rx/Exciter & Control PCB and pull the front panel forward

clear of the frame.

To remove the PCB:

1. Remove the three control knobs (secured by nuts under removable

caps).

2. Carefully pull off the knobs on the three switches located above the

control knobs.

3. Remove the nut securing the volume control.

4. Remove the connector to the microphone socket.

5. Remove the four retaining screws and carefully withdraw the PCB.

To install the PCB:

1. Reverse the procedure detailed above.

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5.4.5 PA and Filter Assembly

The PA output transistors can be replaced without removing the PCB from

the heatsink. Refer to paragraph 5.3.6.

Many of the components on the PCB are accessible once the PA assembly is

removed from the main frame. Do not remove the PCB from the heatsink

unless absolutely necessary.

To remove the PA PCB assembly:

1. Disconnect the ribbon connector P1 and the twin coaxial connector P2.

2. Remove the four retaining screws securing the rear panel to the main

frame (two at each end of rear panel).

3. Remove the six screws securing the PCB to the septum panel:

•one at each corner of the PCB (4 off)

•one close to Tx/Rx relay K7

•one longer screw (16 mm) located between output transistor V14

and the Driver Heatsink.

4. Carefully withdraw the PCB assembly from the main frame.

To remove the PCB from the heatsink:

1. Remove the PA assembly as detailed above.

2. Unsolder and remove the three capacitors C87 to C89 mounted

between the bases of the output transistors V18 and V19.

3. Unsolder the wires and solder lugs fitted to the antenna sockets.

4. If the PCB is to be changed, unsolder and remove the negative and

positive power leads from their mountings on the PCB.

5. Remove the four screws securing the output transistors V18 and V19.

6. Remove the remaining three screws securing the PCB to the heatsink.

Note: The 12mm long screw removed from the driver heatsink must

be returned to this position when re-assembling.

7. Lift the PCB from the heatsink taking care not to damage the

thermistor (R22) and transistor V16 recessed into the heatsink. Take

care not to lose the mica insulator fitted under transistor V17.

To install the PCB to the heatsink:

1. Clean the underside of the output transistors V18/V19[E11] and bias

transistor V17. Clean the mating surfaces on the heatsink. Recoat

these surfaces with new thermal compound (e.g. Jermyn Theraflow

A30). Refit the mica insulator (if previously removed) coated with

thermal compound. Check there is sufficient thermal compound in the

two holes that locate the thermistor R22[F4] and transistor V16[G9].

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2. Carefully refit the PCB to the heatsink taking care to locate R22 and

V16 into their appropriate holes and check the mica insulator remains

in place under transistor V17.

3. Loosely fit all screws (ensuring the longer screw is located in the driver

heatsink), then tighten.

4. Reconnect the wires and solder lugs to the antenna sockets. Install the

DC input power leads. Take care not to overheat the plastic insulation.

To install the PA PCB assembly to the main frame:

1. Carefully slide the assembly from the rear of the transceiver onto the

septum panel. At the same time locate the Antenna Control connector

J401 through the cut-out in the rear panel.

2. Once in position, refit all screws and tighten.

Note: The 16mm long screw is fitted in the hole located between

transistor V19 and the driver heatsink securing the PCB via the

heatsink to the septum panel.

Depending on the nature of the repair it may be necessary to reset the bias

and power levels. Refer to PA adjustments in Chapter 7 for details.

5.4.6 Replacement of PA Transistors

The PA output transistors, V18[E11] and V19, should only be replaced in

matched pairs. The gain groupings of the SRFH1008 (selected MRF455)

transistors are identified by a coloured dot or letter code. Only transistors of

the same dot colour or code should be fitted.

The PA output transistors can be replaced without removing the PA and

Filter PCB from the heatsink. It is necessary to release only the screws

securing the transistors and to unsolder connections as follows:

1. Unsolder and remove the capacitors C87[E10] to C89 located between

the bases of the transistors.

2. Unsolder and lift the driver transformer T3 secondary winding from the

transistor bases.

3. Cut and remove the cable tie supporting the output transformer T4 to

the PCB.

4. Unsolder and lift the output transformer T4 primary winding from the

transistor collectors.

5. Remove the flange fixing screws.

6. Use a desoldering tool or 'solder wick' to remove the bulk of the solder

at each connection. Remove the solder lugs from the emitters of the

transistors. Gently pull the transistor legs away from the PCB while

heating the joints.

7. Clean away excess solder from transistor pads on the PCB.

Maintenance 5-12 X-2 Technical Service Manual

Publication No: 15-02047

8. Clean the transistor mating surface on the heatsink with a cloth or

tissue.

9. Coat the transistor flange with a thin film of thermal compound

(eg. Jermyn Thermaflow). Check the orientation and fit the new

transistors.

10. Refit the four flange mounting screws complete with the three solder

lugs. Tighten the screws evenly.

11. Carefully solder the transistor connections. This should be carried out

quickly using a very hot tipped soldering iron.

12. Refit the output transformer complete with new cable tie, driver

transformer and capacitors C87 to C89.

13. Re-adjust the bias current. Refer to Chapter 7 - Adjustments

Section 7.11.

X-2 Technical Service Manual 6-1

Publication No: 15-02047

6Channel Additions

Channel additions can be programmed from the microphone socket using an

IBM compatible PC, or cloned from a second transceiver.

Details on how to program or clone information from another transceiver can

be found in the XP User Guide supplied with the XP software.

Two cables are provided with the XP software package:

•one to connect the computer to the microphone socket

•one to clone information from another X-2 Transceiver.

Chapter 8 details the pin connections and functions of the front and rear

connectors.

Channel Additions 6-2X-2 Technical Service Manual

Publication No: 15-02047

X2 Technical Service Manual 7-1

Publication No: 15-02047

7Adjustments

7.1 Introduction

Preset adjustments, which are normally factory-set, will require attention

only if components that affect their settings are replaced. The X-2

Transceiver is provided with a special Test Mode, detailed in Section 7.5, to

assist in alignment and checks of filters, local oscillators and channel

frequencies.

7.2 Test Equipment Required

•Oscilloscope 50 MHz, complete with a 10X probe with a 10 MΩ and

less than 15 pF input impedance.

•RF Dummy Load 50Ω and Power Meter rated at 100 W RMS

minimum.

•RF Signal Generator covering the range of 400 kHz to 18 MHz.

Calibrated output signals from 10 millivolt to 0.5 µV from a source

impedance of 50 Ω.

•Frequency Counter 50 MHz with a resolution of 1 Hz.

•Regulated Power Supply of 13.6 V ± 0.2 V at 20 A peak.

•Two tone Audio Generator operating at 700 Hz and 2300 Hz complete

with 3 dB balance control and adjustable output 0-100 mV RMS.

•Digital Multimeter 10 MΩ input impedance.

•Transceiver Test Unit to Codan drawing 04-01868.

Note: The microphone isolating transformer should be fitted with a

mu-metal screen to prevent mains 50 Hz pickup.

•Resistance Box fitted with E12 series resistor range 10 Ω to 1 MΩ

assists in the selection of the SOT resistors.

•Spectrum Analyser for intermodulation measurements if required.

7.3 Voltage Regulators

None of the voltage regulators are adjustable. Only the output voltages can

be checked at the following locations:

104-02907 Sheet 1 and 3

1. On the Rx/Exciter & Control PCB:

•TP402[B10] 'B' rail regulated DC (IC401) +10 V ± 0.2 V.

•TP403[C7] +5V - A regulated DC (IC402) +5 V ± 0.4 V.

•TP8[D5] +5V - B regulated DC (IC3) +5 V ± 0.4 V.

•TP6[A4] Switched DC supply (IC7/C), B rail voltage in

receive, 0 V in transmit.

•• TP7 Switched DC supply (IC7/D), B rail voltage in

transmit, 0 V in receive.

Adjustments 7-2X-2 Technical Service Manual

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104-02908

2. On the PA PCB:

•+5V regulated DC supply selected in transmit only (IC2) +5 V

± 0.4 V. No test point provided but it can be checked at a number

of places. For example: R11[F2] or PTC R22[E4].

•Zener shunt controlled DC supply to IC1[C4] (V1) +5 V ±0.25 V.

This can be checked at pin 5 of IC1.

7.4 Crystal Oven

108-04840

The Crystal Oven, on the Rx/Exciter & Control PCB, is attached to the

Reference Crystal Z3[D3]. The oven should be checked after allowing five

minutes warm-up period. The temperature operates between 50°C to 65°C

and is not adjustable. Replace if the results are outside the specified limits.

7.5 Test Mode

The X-2 Transceiver is provided with a special Test Mode to assist in the

following procedures:

•Alignment of the 45 MHz roofing filter using only an Oscilloscope, a

Signal Generator and a simple jig made from an 18 Ω resistor and 470

µF capacitor attached to clip leads.

•Alignment of the T5 and T6 in the 455 kHz IF circuit.

•Checking of VCO1 (not adjustable).

•Checking and adjusting of VCO2.

•Adjustment of the USB channel frequency.

•Adjustment of the LSB channel frequency.

•Checking the PA. The band switching, the intermodulation distortion at

the top, bottom, and centre of each filter band.

•Adjustment of receiver sensitivity at 15 selected frequencies between

2 MHz to 18 MHz.

To select the Test Mode:

1. Switch off the Transceiver.

2. On the Rx/Exciter & Control PCB , remove the shorting link parked

on the two ground pins of Link 1 and 2 and fit to Link 1.

3. Switch on the Transceiver, which is now in the Test Mode.

X-2 Technical Service Manual Adjustments 7-3

Publication No: 15-02047

4. In the Test Mode the channel switch has a 12 position function and the

USB/LSB operates as an extension to the channel switch providing

additional channel positions plus other special functions detailed in

Table 7.1.

5. To return to Normal Mode: Switch off Transceiver, remove link from

Link 1, return it to its normal parking position (ground pins of link 1

and 2). The transceiver will now be in its normal operating mode.

Channel

position Switch to USB

Test frequency and function Switch to LSB

Test frequency and function

1. 2.00 MHz, USB, Band 1, Ant.1 11.6 MHz, USB, Band 5, Ant.1

2. 2.50 MHz, USB, Band 1, Ant.1 15.5 MHz, USB, Band 5, Ant.1

3. 3.00 MHz, USB, Band 1, Ant.1 17.9 MHz, USB, Band 5, Ant.1

[For USB frequency check]

4. 3.10 MHz, USB, Band 2, Ant.1 17.903 MHz, LSB, Band 5, Ant.1

[For LSB frequency adjust]

5. 3.50 MHz, USB, Band 2, Ant.1 18.0 MHz, USB, Band 5, Ant.2*

For Ant.2 and Talk Power check.

6. 4.70 MHz, USB, Band 2, Ant.1 Not used

7. 4.80 MHz, USB, Band 3, Ant.1 45 MHz filter alignment

[For use with CRO & Sig. Gen]

8. 5.50 MHz, USB, Band 3, Ant.1 VCO1 and 2 centre frequency

9. 7.40 MHz, USB, Band 3, Ant.1 VCO1 and 2 lowest frequency

10. 7.50 MHz, USB, Band 4, Ant.1 VCO1 and 2 highest frequency

11.*8.50 MHz, USB, Band 4, Ant.1 45 MHz filter alignment

[Use with Spectrum Analyser]

12.*11.5 MHz, USB, Band 4, Ant.1 Not used

Table 7.1: USB/LSB Test Frequencies and Functions

Note:With the exception of channel position 5 - LSB, all other channel

positions have Talk Power Select Off (pin 8 IC405 low). This enables

the two-tone signal to be viewed on the Oscilloscope without the

associated ripple in talk power mode.

*Channel positions 11 and 12 are not shown on the front panel

escutcheon.

Adjustments 7-4X-2 Technical Service Manual

Publication No: 15-02047

7.6 VCO Checks and Adjustments

7.6.1 VCO1 Check

108-04840

There is no adjustment for VCO1 located on the Rx/Exciter & Control PCB

but a check can be made as follows:

1. Select Test Mode (refer to Section 7.5).

2. Select channel position 8 and USB/LSB to LSB.

3. Ensure the screening can is fitted over VCO1[C4] and Mixer 1 for the

following test.

4. Connect a DC voltmeter to TP3[C4] and check for a reading of 7.7 V

± 1.0 V. The frequency at TP4 should measure approximately

55 MHz.

5. Select channel position 9.

6. Check the voltage at TP3 reads 3.2 V ± 0.7 V. The frequency at TP4

should measure approximately 47 MHz.

7. Select channel position 10.

8. Check the voltage at TP3 reads 12.7 V ± 1.5 V. The frequency at TP4

should measure approximately 63 MHz.

9. Should any of the measurements not be within the stated limits, check

the VCO1 and associated circuits for possible faults.

7.6.2 VCO2 Check

108-04840

VCO2 located on the Rx/Exciter & Control PCB can be checked as follows:

1. Select Test Mode (refer to Section 7.5).

2. Select channel position 9 and USB/LSB to LSB.

3. Connect a DC voltmeter to TP13[D6] and check for a reading of

3.0 V ± 0.5 V. The frequency at TP10[C7] should measure

approximately 44.5405 MHz.

4. Select channel position 8.

5. Check the voltage at TP13 reads 8.0 V ± 1.5 V. The frequency at

TP10 should measure approximately 44.5445 MHz.

6. Select channel position 10.

7. Check the voltage at TP13 reads between 11.0–15.7V. The frequency

at TP10 should measure approximately 44.5485 MHz.

8. Should the measurements not be within the stated limits, adjust VCO2

as detailed in section 7.6.3 VCO2 Adjust.

X-2 Technical Service Manual Adjustments 7-5

Publication No: 15-02047

7.6.3 VCO2 Adjust

108-04840

To adjust VCO2:

1. Select Test Mode (refer to Section 7.5).

2. Select channel position 8 and USB/LSB to LSB.

3. Short together TP11[D7] and TP12.

4. Connect an Oscilloscope to TP13[D6] using the following settings:

•Y input to 5 V per division (0.5 V/division if using 10X probe)

•Timebase to 2 µs per division.

5. Commencing from the bottom of the coil, adjust L15[C6] tuning core for

minimum repetition rate. Remove the short from TP11 and TP12.

ICAUTION

Great care must be taken to use the correct trimming tool to prevent

damage to the tuning core.

6. Select channel position 9.

7. Connect a DC voltmeter to TP13. Commencing from the bottom of

inductor L17, adjust the tuning core for a reading of 3.0 V ± 0.2 V.

Frequency at TP10 should measure approximately 44.5405 MHz.

8. Select channel position 8.

9. Check the voltage at TP13 reads 8.0 V ± 1.5 V. The frequency at

TP10 should measure approximately 44.5443 MHz.

10. Select channel position 10.

11. Check the voltage at TP13 reads between 11.0–15.7 V. The frequency

at TP10 should measure approximately 44.5485 MHz.

7.7 45 MHz Filter Alignment

108-04840

There are two methods of aligning the 45 MHz roofing filter located on the

Rx/Exciter & Control PCB:

1. Using an Oscilloscope and a Signal Generator.

2. Using a Spectrum Analyser with Tracking Generator.

Both methods are detailed in the following two sections.

Adjustments 7-6X-2 Technical Service Manual

Publication No: 15-02047

7.7.1 Alignment - Method 1

The following steps detail the alignment procedure using an Oscilloscope and

a Signal Generator:

1. Select the Transceiver Test Mode (refer to Section 7.5).

2. Select channel position 7 and the USB/LSB to LSB.

3. Connect a 470 µF 16 V electrolytic capacitor in series with an 18 Ω

resistor between TP3[C3] and 0 V (-ve of capacitor to 0 V).

4. Remove the shorting link parked on the two ground pins of Link 3 and

4[D5] and fit to B-E of N/L TP15. This will open the noise limiter gate.

5. Connect and set a Signal Generator to a frequency of 8.4 MHz

± 100 Hz and an output of 6.3 mV EMF to the receiver input.

6. Connect an Oscilloscope with a 10X probe to TP14[B7]. Connect

External Trigger input to Trig[D4] Test Point on the PCB. Set the

Oscilloscope to the following settings:

•Channel One to 20mV/division (this equals 0.2V/division with

the attenuation of the 10X probe).

•Timebase to 2ms/division.

•Trigger External. Adjust the trigger for a constant sweep.

7. Adjust transformers T3[B6] and T4 and inductor L10 for minimum ripple

response. (Refer to Figure 7.1.)

Figure 7.1: Ripple Response

8. Remove the shorting link to B-E and return it to its parking position

(ground pins of Link 3 and 4).

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Publication No: 15-02047

7.7.2 Alignment - Method 2

The following steps detail the alignment procedure using a Spectrum Analyser

and Tracking Generator:

1. Select the Transceiver Test Mode (refer to Section 7.5).

2. Select channel position 11 and the USB/LSB to LSB.

3. Remove the shorting link parked on the two ground pins of Link 3 and

4[D5] and fit link to B-E of N/L TP15. This will open the noise limiter

gate.

4. Connect the Tracking Generator set to an output of 7 mV RMS

(-30 dBm) direct to the receiver input (P1 pin 1 and ground pin 2) on

the Rx/Exciter & Control PCB. This will by-pass the Broadcast Filter.

5. Connect the Spectrum Analyser input to TP14[B7] (50 Ω input is

permitted). Set up the Spectrum Analyser as follows:

•Centre frequency to 455 kHz.

•Frequency span to 100 kHz (10 kHz/Div).

•Reference set to 10 dB per division.

6. Adjust the Spectrum Analyser sensitivity to about -50 dBm to display

the frequency response of the 45 MHz roofing filter.

7. Adjust transformers T3[B5] and T4 and inductor L10 for less than 2 dB

ripple over 15 kHz span centred at 455 kHz. If desired, the reference

level can be changed to 2 dB per division to improve resolution.

Note:In this Test mode VCO1 and VCO2 are set to 44.544 MHz

enabling the receive frequency to equal the 455 kHz IF

frequency. This allows the Spectrum Analyser and Tracking

Generator to be used to align the roofing filter at 455 kHz.

8. Remove the shorting link to B-E and return it to its parking position

(ground pins of Link 3 and 4).

7.8 455 kHz IF and N/L Alignment

108-04840

There are two tuned transformers in the 455 kHz IF circuit located on the

Rx/Exciter & Control PCB:

•T5 in the IF path to the Sideband Filter.

•T6 is located at the output of the noise limiter 455 kHz amplifier.

The alignment may be carried out either in the Test Mode or normal

operating mode.

To align the two transformers:

1. Select any receive channel.

2. Connect a Signal Generator set to 1 kHz above the selected channel

frequency (1 kHz below for LSB) at an output of about 10 mV EMF

to the receiver input.

Adjustments 7-8X-2 Technical Service Manual

Publication No: 15-02047

3. Fit a shorting link to B-E to disable the noise limiter gate (located at

the rear of the Rx/Exciter PCB adjacent to the Antenna control

connector J401[A10]).

4. Connect an Oscilloscope using a 10X probe to TP14[B7]. Set the

Oscilloscope to the following:

•Timebase to 50 µs/division.

•Channel One to 50mV/division (equals 0.5V/division with the

attenuation of the 10X probe).

•Trigger set to auto sweep.

5. Adjust T5[B7] for maximum amplitude.

Note:Only a small change in amplitude will be seen due to the low Q

of the tuned circuit.

6. Remove the 10X probe from TP14.

7. Connect a 1X probe to position A (part of N/L TP15). Set the

Oscilloscope to a sensitivity of 10 mV/division.

8. Adjust T6[A7] for maximum amplitude.

9. Remove the shorting link to B-E and return it to its parking position

(ground pins of Link 3 and 4).

10. Remove the 1X probe from position A.

7.9 Frequency Adjustment

108-04840

All the channels are synthesised and locked to the 7304 kHz reference crystal

(Z3) oscillator. The reference crystal divided (7304 kHz ÷ 16) provides the

local oscillator to the Modulator and Demodulator in USB mode. Therefore

it is only necessary to adjust the reference frequency for all channels on USB.

An additional divided crystal oscillator (1814 kHz ÷ 4) provides the local

oscillator to the Modulator and Demodulator in LSB mode.

7.9.1 Frequency Adjust USB

To adjust the USB frequency:

1. Select the Transceiver Test Mode (refer to Section 7.5)

2. Select channel position 3 and the USB/LSB to LSB (this selects test

channel 17900 kHz USB).

X-2 Technical Service Manual Adjustments 7-9

Publication No: 15-02047

3. Remove the coaxial connector P1 on the Rx/Exciter & Control PCB

(removing the exciter output to the PA).

4. Connect a Frequency Counter to Exciter output (Tx and ground).

5. Hold the Tune/Off/Mute switch in the Tune position.

6. Adjust trimmer C51[D3] (reference crystal adjust) to a frequency of

17900 kHz ± 5 Hz.

Note:Allow at least five minutes from switch-on before adjusting the

frequency.

7.9.2 Frequency Adjust LSB

To adjust LSB for frequency:

1. First adjust frequency in the USB as detailed in Section 7.9.1. Remain

in the Test Mode and leave the frequency counter connected.

2. Select channel position 4 and the USB/LSB to LSB (this selects test

channel 17903 kHz LSB).

3. While holding the Tune/Off/Mute switch in the Tune position adjust

C97[E7] for 17903 kHz ± 5 Hz.

7.10 Mute Adjustment

108-04840

The Mute is located on the Rx/Exciter & Control PCB. The adjustment

procedure is as follows:

1. Connect the Transceiver to an antenna (a short length of wire will do).

Select an unoccupied channel.

2. Select Mute On located on the front panel.

3. Commence with preset potentiometer R358[E8] fully counter-clockwise.

Slowly rotate the control clockwise until the mute gate closes and the

receiver noise is heard in the loudspeaker (mute threshold).

4. Rotate the control back in a counter-clockwise direction for 1/4 of a

turn.

5. The mute should now be sensitive enough to operate on the weakest

signal without false triggering on noise pulses. The sensitivity may be

varied from this setting to suit individual requirements (clockwise to

increase sensitivity).

Adjustments 7-10 X-2 Technical Service Manual

Publication No: 15-02047

7.11 PA Adjustments

7.11.1 Driver Bias

To check and adjust the driver bias:

1. Disconnect exciter output to the PA by removing connector P2 on the

PA PCB assembly.

2. With the Transceiver off, unsolder Link DR (DC supply to the driver

transistors V13 and V14). Connect a Multimeter set to DC current

100 mA in place of the removed link (+ve to the right).

3. Switch on the Transceiver selected to any transmit channel and operate

the PTT (transmit mode). Check the driver current measures 18 mA

± 3 mA.

4. If the current is out of the specified limit stated in step 3 it can be

changed by selecting an alternative SOT resistor R39.

5. Switch off the Transceiver, disconnect Multimeter and replace Link

DR with a length of 22 gauge TCW.

7.11.2 PA Bias

To check and adjust the output PA transistors bias:

1. Disconnect exciter output to the PA by removing connector P2 on the

PA PCB assembly.

2. With the Transceiver off, unsolder Fuse PA/OP (DC supply to the

output transistors V18 and V19). Connect a Multimeter, set to DC

current 1A, in place of the removed fuse (+ve to the left).

3. Switch on the Transceiver selected to any transmit channel and operate

the PTT (transmit mode). Check the output transistor current measures

120 mA ± 10 mA.

4. If the current is out of the specified limits stated above, adjust preset

potentiometer R45[C5] to the correct current level.

5. Switch off the Transceiver and replace Fuse PA/OP with three strands

taken from a piece of ribbon cable. Solder the wire to the two stakes

extending the centre of the wire up to form an inverted Vee. Only

solder at the wire ends attached to the stakes.

X-2 Technical Service Manual Adjustments 7-11

Publication No: 15-02047

7.11.3 Output Power

To set the output power:

1. Ensure the Exciter output is connected to the PA PCB Assembly (P1

to P2).

2. Select channel position 5 and the USB/LSB to USB. This selects the

channel frequency 3500 kHz, USB, and Antenna 1 O/P.

3. Connect an RMS or PEP Power Meter with a 50 Ω Dummy Load to

Antenna 1 connector.

4. Connect the Oscilloscope via a 47 kΩ resistor to Antenna 1 connector.

Alternatively a Tee piece with an attenuated output of approximately

40 dB can be connected to the oscilloscope.

5. Set the Oscilloscope to the following settings:

•Timebase to 500 µs/division

•Trigger set to auto sweep.

6. Apply the two tone audio via the Test Unit to the microphone socket.

7. Select the Transceiver Test Mode (refer Section 7.5).

8. Select transmit (PTT) and adjust the two tone level for microphone

compression.

9. Adjust the Oscilloscope 'Y' sensitivity for on-screen display and adjust

the trigger for a stationary waveform.

10. Adjust the two tone balance control for good crossover display.

11. Select a value for the Set PWR SOT resistor R14[C3] on the PA PCB

for the following output power:

•For Australian use - 100 W PEP. Link X should be fitted to

prevent reduced power at 18 MHz.

•For use outside Australia - 125 W PEP. Link X should not be

fitted. This will allow the output power to fall to about 100 W at

18 MHz.

Note:The indicated PEP level with two tone modulation will depend

upon the type of measuring instrument as shown in Table 7.2.

Power output PEP 100 W 125 W

Peak reading meter 100 W 125 W

RMS reading meter 50 W 62.5 W

Average reading meter

(Bird Model 43) 40.5 W 50.6 W

Table 7.2: Power output PEP vs Measuring Instrument

12. Check the two tone waveform is clean and undistorted.

13. The output power is factory set and not likely to be outside the

specified limits. First check there are no faults with the transmitter

circuits before attempting to adjust the power output.

Adjustments 7-12 X-2 Technical Service Manual

Publication No: 15-02047

7.11.4 Intermodulation

The Test Mode provides 15 channel frequencies to check the PA on the five

bands. One at the start of each band, one in the centre, and finally one at the

top of each band.

A Spectrum Analyser is required to test the Intermodulation Distortion

(IMD). The check procedure is as follows:

1. Ensure the Exciter output is connected to the PA PCB Assembly

(P1 to P2).

2. Connect a 50 Ω Dummy Load to Antenna 1 output via a suitable in-

line Tee piece to provide a low level output to connect to a Spectrum

Analyser.

3. Select the Transceiver Test Mode (refer Section 7.5).

4. Select first channel position 1 and the USB/LSB to USB. This selects

the channel frequency 2000 kHz, USB, and Antenna 1 O/P.

5. Apply the two tone audio (700 Hz and 2300 Hz) via the Test Unit to

the microphone socket.

6. Set up the Spectrum Analyser as follows:

•Centre frequency to 2000 kHz.

•Frequency span to 20 kHz (2 kHz/div).

•Reference to 10 dB/division.

•Video bandwidth to 300 Hz.

•Sensitivity will depend on the signal level applied to the Analyser

and will require adjustment when transmitting.

7. Select PTT (Tx mode) and adjust the two tones for compression. If

this level is unknown it can be checked by observing the output of the

Microphone Amplifier at TP302 using an Oscilloscope for 500 mV pp.

8. Adjust the two tones for equal amplitude displayed on the Spectrum

Analyser by operating the balance control on the two tone Signal

Generator. Adjust the Sensitivity control on the Spectrum Analyser to

set the two tones at the top of the screen.

9. The Intermodulation distortion levels at 2000 kHz can be measured

with respect to each tone. Add 6 dB to the reading if referenced to

PEP (refer Specifications Section 1.6.3 for limits).

10. The Intermodulation distortion can be checked on the other available

14 frequencies by selecting the Test Mode channels detailed in Table

7.1 in Section 7.5. The Spectrum Analyser centre frequency will need

to be set to the channel frequency selected.

Note:By adjusting the Spectrum Analyser frequency span it is also

possible to check the Spurious and Harmonic components during

the IMD checks.

X-2 Technical Service Manual Adjustments 7-13

Publication No: 15-02047

7.12 Receiver Performance Checks

7.12.1 Sensitivity and S+N/N ratio

Connect an AC Voltmeter across the audio output. Set the Signal Generator

frequency 1 kHz above the SCF of the selected channel (1 kHz below for

LSB) and connect the output, set to 0.4 µV PD, to the selected Antenna

socket. Adjust the volume control for a suitable near full scale dB reading on

the AC Voltmeter. Take note of the reading.

Switch off or adjust the Signal Generator output to a frequency outside the

receiver passband and check that the audio output drops by at least 10 dB.

7.12.2 AGC Check

Set up as for the Sensitivity test (refer to Section 7.12.1) but with the Signal

Generator output set to 50 mV PD. Adjust the volume control for a suitable

near full scale dB reading on the AC Voltmeter. Take note of the reading.

Reduce the Signal Generator output until the receiver output drops by 6 dB.

The Signal Generator level should be less than 2.5 µV PD.

7.12.3 Audio Output

Set up as for the Sensitivity test (refer to Section 7.12.1) but with the Signal

Generator output set to 50 µV PD. Connect an Oscilloscope in parallel to

the AC Voltmeter across the audio output.

Increase the Volume control and check the audio output exceeds 4 V RMS

at the onset of clipping displayed on the Oscilloscope.

Note:For this test it is permissible to replace the loudspeaker with a 5 W

8 Ω resistor.

7.12.4 Selectivity (USB operation)

Set up as for the Sensitivity test (refer to Section 7.12.1) but with the Signal

Generator output set to 0.5 µv PD and note the audio output reference level

on the AC meter.

With a Frequency Counter monitoring the Signal Generator, adjust the

frequency to -1 kHz and then to +4 kHz from SCF. Increase the Signal

Generator to 0.5 mV PD (+60 dB above 0.5 µV) and check the audio output

is less than the reference level at both frequencies.

Adjustments 7-14 X-2 Technical Service Manual

Publication No: 15-02047

7.12.5 Clarifier Operation

Set the Signal Generator frequency 1 kHz above the SCF of the selected

channel (1 kHz below for LSB) and connect the output, set to any level

between 0.4 µV and 10 µV PD, to the selected Antenna socket.

Check the audio frequency changes with rotation of the Clarifier in a

clockwise and counter-clockwise direction. Check also that pips are heard at

the limits of each end of the control.

7.12.6 Noise Limiter Operation

Set the Signal Generator frequency 1 kHz above the SCF of the selected

channel (1 kHz below for LSB) and connect the output, set to 0.4 µV PD,

via a Tee piece to the selected Antenna socket.

To the unoccupied socket of the Tee piece add a BNC to Two-Terminal

adaptor. Connect the output of a Square-wave Generator via a 100 pF

capacitor to the adaptor. Set the Square-wave Generator frequency to a

100 Hz and the output to 5 V peak to peak.

The Noise Limiter is normally ON and the signal produced by the Signal

Generator should be clearly heard over the interfering signal from the

Square-wave Generator.

When the Noise Limiter is switched off, by shorting A to E on N/L test point

on the Rx/Exciter & Control PCB, the noise from the Square-wave

Generator should swamp the wanted signal from the Signal Generator. This

test will verify the Noise Limiter is functioning correctly.

7.13 Transmitter Performance Checks

7.13.1 Frequency Check

Check as detailed in the Frequency Adjustment Section 7.9.

X-2 Technical Service Manual Adjustments 7-15

Publication No: 15-02047

7.13.2 ALC

Use the Transceiver Test Unit with two tone audio source to modulate the

transmitter. In the transmit mode, slowly increase the audio output until the

output power just ceases to increase (ALC threshold).

Note the PEP output and increase the audio input by 20 dB. The increase in

output should be less than 0.5 dB above the ALC threshold.

7.13.3 Power Output and Intermodulation

For Australian use:

Power output 100 W PEP ± 0.5 dB (solder Link 'X' fitted). Intermodulation

distortion should be better than -32 dB below PEP (-26 dB below each tone)

as measured with a Spectrum Analyser. Use 700 Hz and 2300 Hz tones.

For use outside Australia:

Power output 125 W PEP at 2 MHz reducing to 100 W at 18 MHz (solder

Link 'X' not fitted). Intermodulation distortion should be better than

-32 db below PEP (-26 dB below each tone) as measured with a Spectrum

Analyser.

Note:The indicated PEP level with two tone modulation will depend upon

the type of measuring instrument used. See Table 7.2 in Section 7.11.3.

7.13.4 Emergency Call

The Emergency Call facility is for use with the Australian Royal Flying

Doctor Service.

The two-tone modulation frequencies of 880 Hz and 1320 Hz are determined

by the software in the Microcontroller. Therefore it is only necessary to carry

out a function check as follows:

1Connect a 50 Ω Dummy Load to the selected Antenna Connector

complete with Power Meter.

2Connect an Oscilloscope via a 47 kΩ resistor to the Antenna

Connector.

3Select a channel with Emergency Call enabled.

4Operate the EMGCY CALL on the front panel and check the

following:

•The output power equals approximately 100 W PEP.

•The two modulating tones are approximately of equal amplitude

(viewed on the Oscilloscope).

•The modulating tones are heard in the loudspeaker.

Adjustments 7-16 X-2 Technical Service Manual

Publication No: 15-02047

X-2 Technical Service Manual 8-1

Publication No: 15-02047

8Appendices

Appendix A: Connectors

The following tables detail the pin connections and functions of the front

and rear connectors. Details are also provided for the cables used for

channel and cloning programming.

A.1 Microphone

Pin No. Function Signal Levels

1PTT Ground 0 V

2PTT Active Active Low

3Microphone Ground 0 V

4Microphone Input 50 mV P-P 8 kΩ I/P Imp.

5Speaker Ground Return * See note below

6Speaker Audio Output 12 V P-P max. 4Ω min.

7Speaker Ground 0 V

Table A.1 Microphone Connector pin function.

*Note: Link pin 5 to pin 7 for front panel speaker operation.

A.2 External Loudspeaker

Pin No. Function Signal Levels

Tip Speaker Audio Output 12V P-P max. 4Ω min.Imp.

Sleeve Ground 0 V

Table A.2 External loudspeaker connector pin function.

8-2 Appendices X-2 Technical Service Manual

Publication No: 15-02047

A.3 Antenna Control

Pin No. Function Signal Levels

1BCD Channel Number 4 Open Collector Active Low

2BCD Channel Number 8 Open Collector Active Low

3No Connection

4No Connection

5No Connection

6No Connection

7No Connection

8PTT Out 100 kΩ Source Active High

9BCD Channel Number 1 Open Collector Active Low

10 BCD Channel Number 2 Open Collector Active Low

11 No Connection

12 A Rail Nominal +12 V

13 A Rail Nominal +12 V

14 Ground 0 V

15 Ground 0 V

Table A.3 Antenna control connector pin function.

A.4 Programming Cable

9 Way Computer

Serial Port Socket 7 Way transceiver

Microphone Socket Pin Function

2 1 Data from Transceiver

3 2 Data to Transceiver

5 *Series Thermistor

(Thermistor =50Ω 80°C)

3Ground

5/7 link Speaker Link

Table A.4 Programming cable connector pin function.

A.5 Cloning Cable

7-Way Transceiver

Microphone Socket 7-Way Transceiver

Microphone Socket Pin Function

1 2 Data I/O

2 1 Data I/O

3 3 Ground

5/7 link 5/7 link Speaker Link

Table A.5 Cloning cable connector pin function.

X-2 Technical Service Manual Appendices 8-3

Publication No: 15-02047

Appendix B: Parts Lists

B.1 General Information

The parts lists for the PCB assemblies contain:

1. Circuit Reference Number.

2. Descriptions, giving the value and type of component.

3. Manufacturer and Manufacturer's Part Number.

4. CODAN Part Number.

Note: Items having numeric references identifying specific

components or subassemblies may be encountered in the parts

lists included in this manual. These items, selected from master

manufacturing information, identify parts which either are useful

for maintenance purposes or relate to other items and may be

cross referenced in the remarks column.

Table B.1 lists the abbreviations for resistor and capacitor types.

Resistors Capacitors

CC- carbon composition AS- solid aluminium electrolytic

CF- carbon film CC- ceramic multilayer chip

MF- metal film CE- ceramic

MG- metal glaze EL- wet aluminium electrolytic

MO- metal oxide M- stacked mica

WW- wire wound PC- polycarbonate

PE- polyester

PP- polypropylene

PS- polystyrene

PT- PTFE

TA- solid tantalum

Table B.1 Resistor and capacitor abbreviations.

8-4 Appendices X-2 Technical Service Manual

Publication No: 15-02047

B.2 Ordering Information

Orders for replacement components must include the following information.

This will ensure that the correct parts are supplied and help speed up

delivery times.

1. Equipment type (e.g. Type X-2 Transceiver).

2. Component location (e.g. Rx/Exciter & Control PCB, 08-04840).

3. Component circuit reference number (e.g. R74).

4. Full component description (e.g. Resistor 470Ω 5% 0,33W CF Res).

5. Manufacturer (e.g. Philips)

6. Manufacturer's Part Number (e.g. 2322 211 13471).

7. CODAN Part Number (e.g. 40-24700-020).

B.3 Component Substitution

When replacing general purpose components (resistors, capacitors etc.),

equivalent parts from other manufactures may be used provided they have

similar tolerances, voltage/power rating and temperature coefficients as

those of the specified part.

Substituting components which do not exactly match those listed in the

parts list will not adversely affect equipment performance.

B.4 Parts Lists

Four parts lists can be found in this section as shown in Table B.2.

Page Title Assembly No

8-5 Sundry Parts 08-04843

8-6 Front Panel Assembly 08-04842-000

8-8 Rx/Exciter & Control 08-04840-001

8-18 PA and Chassis Assembly 08-04841-001

Table B.2 Parts list index

X-2 Technical Service Manual Appendices 8-5

Publication No: 15-02047

Appendix C: Engineering Drawings

The Engineering Drawings in this appendix consist of the mechanical and

electrical diagrams required to maintain the X-2 Transceiver.

The List of Drawings in Table C.1 details their order of appearance in this

appendix.

Title Drawing No

Mechanical Layout 16-00107

X-2 Block Diagram 03-00876

Interconnection Diagram 04-02910

Front Panel 04-02909

Front Panel PCB Assembly 08-04842

Rx/Exciter & Control (3 Sheets)

- RF & Dual Synthesiser 04-02907 Sheet 1

- 455kHz IF & Audio 04-02907 Sheet 2

- Micro & Peripherals 04-02907 Sheet 3

Receiver/Exciter Assembly 08-04840

PA & Filter 04-02908

PA & Filter PCB Assembly 08-04841

Table C.1 List of Drawings.

8-6 Appendices X-2 Technical Service Manual

Publication No: 15-02047

X-2 Technical Service Manual Appendices 8-7

Appendix D: Glossary of Terms

D.1 Abbreviations

Abbreviation Meaning

A/D Analog to digital

AGC Automatic Gain Control

ALC Automatic level control

BTransducer

B-E Base - Emitter

BCD Binary-coded decimal

CCapacitor

CMOS Complementary metal oxide semiconductor

CPU Central processing unit

CRO Cathode-ray oscilloscope

CW Continuous wave; Carrier wave

DDiode - small signal and power

DC Direct current

EHeating devide

EEPROM Electrically erasable/programmable read-only memory

EMF Electromotive force

Emgcy Emergency

FET Field-effect transistor

FWD-PWR Forward Power

HSignalling/indicating device; Lamp; Buzzer

HF High Frequency

I/O Input/Output

I2CInter IC Communication

IC Integrated Circuit

IMD Intermodulation distortion

IF Intermediate Frequency

JJack Socket

KRelay; Key Switch

LInductor

LED Light Emitting Diode

LSB Lower Side Band

MIC Microphone

NAND Not AND logic

O/P Output

OR Logical OR function

NOR Negative OR function

PPlug

PA Power amplifier

PA/OP Power amplifier/Output

PC Personal computer

PCB Printed circuit board

PD Potential difference

PEP Peak envelope power

PLL Phase-locked loop

ppm Parts per million

PTC Positive temperature coefficient (Resistor)

8-8 Appendices X-2 Technical Service Manual

Publication No: 15-02047

Abbreviations (cont'd)

Abbreviation Meaning

PTT Push-to-talk

PWR Power

QQuality factor

RResistor

RAM Random Access Memory

REF-PWR Reference-Power

RF Radio frequency

RFDS Royal Flying Doctor Service

RMS Root mean square

ROM Read Only Memory

Rx Receive; Receiver

SSwitch

SCF Suppressed carrier frequency

SINAD Signal + Noise + Distortion-to-Noise + Distortion Ratio

SOT Select on test

SSB Single Side Band

TTransformer

TCW Tinned copper wire

TP Test point

Tx Transmit; Transmitter

UHF Ultra High Frequency

USB Upper Side Band

VCO Voltage-controlled oscillator

VSWR Voltage standing wave ratio

ZQuartz Crystal; Crystal Filter; Frequency Network

Table D.1 Abbreviations.

D.2 Units

Abbreviation Unit Abbreviation Unit

Aampere mmetre

°C Celsius (degrees) min minute

Ccoulomb NNewton

dB decibels Pa Pascal

Ffarad SSiemens

ggram ssecond

hhour TTelsa

Hhenry Vvolt

Hz Hertz Wb weber

Jjoule Wwatt

KKelvin Ωohm

llitre

Table D.2 Abbreviations of Units.

X-2 Technical Service Manual Appendices 8-9

D.3 Unit Multiples

Abbreviation Prefix Numeric Meaning

Ttera 1012 one million million

Ggiga 109one thousand million

Mmega 106one million

kkilo 103one thousand

hhecto 102one hundred

da deca 10 ten

ddeci 10-1 one tenth

ccenti 10-2 one hundreth

m milli 10-3 one thousandth

µmicro 10-6 one millionth

nnano 10-9 one thousand millionth

ppico 10-12 one million millionth

Table D.3 Abbreviations of Unit Multiples.

HF SSB Transceiver X2 Technical Service Manual 12-50093 Issue 1, Page 1

Addendum

The following section is added to the HF SSB Transceiver X2 Technical Service

Manual, Codan part number 15-02047 Issue 2, December 1993.

This addendum provides information on changes to the Crystal Oven.

The Crystal Oven information is provided in addition to that existing in Chapter 4,

Local Oscillators. It describes how the oven maintains a constant temperature.

Drawings associated with the crystal oven information are:

• Crystal Oven Circuit Diagram 04-03095

• Crystal Oven Final Assembly 08-05235

The corresponding parts list is:

• Crystal Oven Parts List 08-05235-001

Addendum

Page 2, 12-50093 Issue 1 HF SSB Transceiver X2 Technical Service Manual

Local Oscillators

Introduction

Each synthesizer is locked to the reference oscillator. This consists of a 7.304 MHz

crystal (Z3) held at a constant temperature by an oven, which is one of the

following:

• a PTC thermistor (E1) at 60°C

• a high stability oven where the R3 NTC (Negative Temperature Coefficient)

resistor measures the temperature of the crystal and causes the op-amp

comparator IC1 to vary the current in the heating element V2 to maintain the

temperature of 65oC to within ±1°C

The temperature of the high stability oven is set by R4. V1, R12 and R13 limit the

maximum current through V2 to approximately 400 mA.

9105 Aka X2/Codan X2 TSM Codan

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