Codan X-2 Service Manual
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
1 Introduction........................................................................................................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
2 Brief 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
3 Operating Instructions...............................................................................3-1
4 Technical 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
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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
5 Maintenance.......................................................................................................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
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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
6 Channel Additions.........................................................................................6-1
7 Adjustments....................................................................................................... 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
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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
8 Appendices.........................................................................................................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
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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
1 Introduction
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 1-2 X-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 1-4 X-2 Technical Service Manual
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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 1-6 X-2 Technical Service Manual
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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.
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X-2 Technical Service Manual 2-1
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2 Brief 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 2-2 X-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 2-4 X-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.
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X2 Technical Service Manual 3-1
Publication No: 15-02047
3 Operating 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 3-2 X-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.
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X2 Technical Service Manual 4-1
Publication No: 15-02047
4 Technical 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 4-2 X-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 4-4 X-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 4-6 X-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 (muteout) 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 4-8 X-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.
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