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Codan X-2 Service Manual

Codan X-2 Service Manual

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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

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  • Page 1 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...
  • Page 2 Head Office International Marketing Offices Codan Pty Ltd Australia, Pacific and South East Asia 81 Graves Street Codan Pty Ltd Newton Suite 24, 818 Pittwater Road SOUTH AUSTRALIA 5074 Dee Why New South Wales Telephone AUSTRALIA 2099 National 08 336 0311...

  • Page 3: Table Of Contents

    Table of Contents 1 Introduction ......................1-1 Purpose......................1-1 How this manual is organised ................1-1 Conventions ....................1-2 Related Documents ..................1-2 Overview ......................1-2 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 General ......................2-1 Control and Switching..................2-2 Synthesiser......................2-2 Receive Path ....................2-3 Transmit Path....................2-4...
  • Page 4 Table of Contents X-2 Technical Service Manual 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 Local Oscillators ...................4-10 4.4.1 Introduction................4-10...
  • Page 5 X-2 Technical Service Manual 5.3.4 Transmitter Failure ..............5-7 5.3.5 Unlocked Synthesiser..............5-7 5.3.6 PA Failure ..................5-8 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...
  • Page 6 Table of Contents X-2 Technical Service Manual 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...
  • Page 7 X-2 Technical Service Manual List of figures Figure Description Page No X-2 PCB Block Diagram Ripple Response List of tables Table Description Page No Drawing Reference Audible Warning Tones Drawing Reference Rx/Exciter PCB Supply Voltages PA PCB Supply Voltages Peak to Peak Voltages...

  • Page 8: Publication No:

    Table of Contents X-2 Technical Service Manual Publication No: 15-02047...

  • Page 9: Introduction

    X-2 Technical Service Manual 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 •...

  • Page 10: Conventions

    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.

  • Page 11: Specifications

    X-2 Technical Service Manual Introduction 1-3 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.
  • Page 12 Introduction 1-4 X-2 Technical Service Manual Indicators Power On/Transmit. Connectors: Microphone/Handset. Front RF - UHF connectors: Qty 2 (programmable). Rear Antenna Control. Extension Loudspeaker. Ω nominal. RF Input/Output impedance Supply Voltage 12 V DC nominal, negative earth. Normal operating range 10.5 to 15 V.

  • Page 13: Receiver Specifications

    X-2 Technical Service Manual Introduction 1-5 1.6.2 Receiver Specifications Dual conversion, superheterodyne. Type 45 MHz and 455 kHz. IF Frequencies 0.3(0.4) µV PD -117(-115) dBm for 10 dB Sensitivity SINAD with > 50 mW audio output. Will withstand 50 V RF from 50 Ω.

  • Page 14: Transmitter Specifications

    Introduction 1-6 X-2 Technical Service Manual 1.6.3 Transmitter Specifications All solid state. Type 100 W PEP ± 0.5 dB may be internally set to Power Output any output between 125 and 25 W PEP. CW or single tone approx. 60% of PEP.

  • Page 15: Brief Description

    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. •...

  • Page 16: Control And Switching

    Brief Description 2-2 X-2 Technical Service Manual 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.

  • Page 17: Receive Path

    X-2 Technical Service Manual Brief Description 2-3 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.

  • Page 18: Transmit Path

    Brief Description 2-4 X-2 Technical Service Manual 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...

  • Page 19: Operating Instructions

    X2 Technical Service Manual 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: Switch the transceiver on by turning the Volume control clockwise until the indicator lamp lights.

  • Page 20: Audible Warning Tones

    Operating Instructions 3-2 X-2 Technical Service Manual BEEPS CONTINUOUS Low Tone High Tone Low Tone High Tone Single Transmit Channel High supply inhibited unavailable voltage Tune Fail Tune Double Double (check complete antenna) Slow repetitive Low supply Repetitive Channel not...

  • Page 21: Technical Description

    X2 Technical Service Manual 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)

  • Page 22: Control And Supply Voltages

    Technical Description 4-2 X-2 Technical Service Manual 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...

  • Page 23: Receive/Transmit Switching

    X-2 Technical Service Manual Technical Description 4-3 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 (I C bus) from the microcontroller feeds a 16 bit output expander IC405...

  • Page 24: Receiver

    Technical Description 4-4 X-2 Technical Service Manual 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.

  • Page 25: Noise Limiter

    X-2 Technical Service Manual Technical Description 4-5 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.

  • Page 26: Automatic Gain Control

    Technical Description 4-6 X-2 Technical Service Manual 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.

  • Page 27: Mute

    X-2 Technical Service Manual Technical Description 4-7 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...

  • Page 28: Volume Control And Audio Amplifier

    Technical Description 4-8 X-2 Technical Service Manual 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.

  • Page 29: Modulator

    X-2 Technical Service Manual Technical Description 4-9 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)

  • Page 30: Local Oscillators

    Technical Description 4-10 X-2 Technical Service Manual 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.

  • Page 31: Vco2 And Pll

    X-2 Technical Service Manual Technical Description 4-11 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.

  • Page 32: 455 Khz Local Oscillator

    Technical Description 4-12 X-2 Technical Service Manual 4.4.4 455 kHz Local Oscillator 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 ÷...

  • Page 33: Micro And Peripherals

    X-2 Technical Service Manual Technical Description 4-13 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.

  • Page 34: Front Panel Controls

    Technical Description 4-14 X-2 Technical Service Manual 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 I C bus.

  • Page 35: Tune

    X-2 Technical Service Manual Technical Description 4-15 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 [ from the Tune switch.

  • Page 36: Microcontroller Reset

    Technical Description 4-16 X-2 Technical Service Manual 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.

  • Page 37: Gain Control Stage

    X-2 Technical Service Manual Technical Description 4-17 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 providing DC to the input and predriver [D3] stages.

  • Page 38: Output Stage And Bias Regulator

    Technical Description 4-18 X-2 Technical Service Manual 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.
  • Page 39 X-2 Technical Service Manual Technical Description 4-19 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.
  • Page 40 Technical Description 4-20 X-2 Technical Service Manual Publication No: 15-02047...

  • Page 41: Maintenance

    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.

  • Page 42: Circuit Boards

    Maintenance 5-2 X-2 Technical Service Manual 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...

  • Page 43: Transmitter Precautions

    X-2 Technical Service Manual Maintenance 5-3 • 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.

  • Page 44: Probe Precautions

    Maintenance 5-4 X-2 Technical Service Manual 5.2.4 Probe Precautions The following should be observed when connecting CRO probes to the Transceiver: 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.

  • Page 45: Voltage Measurements

    X-2 Technical Service Manual Maintenance 5-5 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).

  • Page 46: No Reception

    Maintenance 5-6 X-2 Technical Service Manual 5.3.3 No Reception 104-02907 sheet 1 For a receive failure: Check the microphone plug is fitted. The link in the plug completes the audio path to the internal loudspeaker. Check the Mute gate is operating and closed.

  • Page 47: Transmitter Failure

    X-2 Technical Service Manual Maintenance 5-7 • 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.

  • Page 48: Pa Failure

    Maintenance 5-8 X-2 Technical Service Manual 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 at pins 13, 12 and 11.

  • Page 49: Top And Bottom Covers

    X-2 Technical Service Manual Maintenance 5-9 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...

  • Page 50: Pa And Filter Assembly

    Maintenance 5-10 X-2 Technical Service Manual 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.

  • Page 51: Replacement Of Pa Transistors

    X-2 Technical Service Manual Maintenance 5-11 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. Loosely fit all screws (ensuring the longer screw is located in the driver heatsink), then tighten.
  • Page 52 Maintenance 5-12 X-2 Technical Service Manual Clean the transistor mating surface on the heatsink with a cloth or tissue. Coat the transistor flange with a thin film of thermal compound (eg. Jermyn Thermaflow). Check the orientation and fit the new transistors.

  • Page 53: Channel Additions

    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. Publication No: 15-02047...
  • Page 54 Channel Additions 6-2 X-2 Technical Service Manual Publication No: 15-02047...

  • Page 55: Adjustments

    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.

  • Page 56: Crystal Oven

    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: •...

  • Page 57: Usb/Lsb Test Frequencies And Functions

    X-2 Technical Service Manual Adjustments 7-3 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.

  • Page 58: Vco Checks And Adjustments

    Adjustments 7-4 X-2 Technical Service Manual 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: Select Test Mode (refer to Section 7.5).

  • Page 59: Vco2 Adjust

    X-2 Technical Service Manual Adjustments 7-5 7.6.3 VCO2 Adjust 108-04840 To adjust VCO2: Select Test Mode (refer to Section 7.5). Select channel position 8 and USB/LSB to LSB. Short together TP11 [D7] and TP12. Connect an Oscilloscope to TP13 [D6] using the following settings: •...

  • Page 60: Alignment - Method 1

    Adjustments 7-6 X-2 Technical Service Manual 7.7.1 Alignment - Method 1 The following steps detail the alignment procedure using an Oscilloscope and a Signal Generator: Select the Transceiver Test Mode (refer to Section 7.5). Select channel position 7 and the USB/LSB to LSB.

  • Page 61: Alignment - Method 2

    X-2 Technical Service Manual Adjustments 7-7 7.7.2 Alignment - Method 2 The following steps detail the alignment procedure using a Spectrum Analyser and Tracking Generator: Select the Transceiver Test Mode (refer to Section 7.5). Select channel position 11 and the USB/LSB to LSB.

  • Page 62: Frequency Adjustment

    Adjustments 7-8 X-2 Technical Service Manual 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] Connect an Oscilloscope using a 10X probe to TP14 .

  • Page 63: Frequency Adjust Lsb

    X-2 Technical Service Manual Adjustments 7-9 Remove the coaxial connector P1 on the Rx/Exciter & Control PCB (removing the exciter output to the PA). Connect a Frequency Counter to Exciter output (Tx and ground). Hold the Tune/Off/Mute switch in the Tune position.

  • Page 64: Pa Adjustments

    Adjustments 7-10 X-2 Technical Service Manual 7.11 PA Adjustments 7.11.1 Driver Bias To check and adjust the driver bias: Disconnect exciter output to the PA by removing connector P2 on the PA PCB assembly. With the Transceiver off, unsolder Link DR (DC supply to the driver transistors V13 and V14).

  • Page 65: Output Power

    X-2 Technical Service Manual Adjustments 7-11 7.11.3 Output Power To set the output power: Ensure the Exciter output is connected to the PA PCB Assembly (P1 to P2). Select channel position 5 and the USB/LSB to USB. This selects the channel frequency 3500 kHz, USB, and Antenna 1 O/P.

  • Page 66: Intermodulation

    Adjustments 7-12 X-2 Technical Service Manual 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.

  • Page 67: Receiver Performance Checks

    X-2 Technical Service Manual Adjustments 7-13 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...

  • Page 68: Clarifier Operation

    Adjustments 7-14 X-2 Technical Service Manual 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.

  • Page 69: Alc

    X-2 Technical Service Manual Adjustments 7-15 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).
  • Page 70 Adjustments 7-16 X-2 Technical Service Manual Publication No: 15-02047...

  • Page 71: Appendices

    X-2 Technical Service Manual Appendices 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. Microphone Pin No. Function...

  • Page 72: Antenna Control

    8-2 Appendices X-2 Technical Service Manual Antenna Control Pin No. Function Signal Levels BCD Channel Number 4 Open Collector Active Low BCD Channel Number 8 Open Collector Active Low No Connection No Connection No Connection No Connection No Connection PTT Out 100 kΩ...

  • Page 73: Appendix B: Parts Lists

    X-2 Technical Service Manual Appendices 8-3 Appendix B: Parts Lists 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.

  • Page 74: 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).

  • Page 75: Appendix C: Engineering Drawings

    Appendices 8-5 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.
  • Page 76 8-6 Appendices X-2 Technical Service Manual Publication No: 15-02047...

  • Page 77: Appendix D: Glossary Of Terms

    X-2 Technical Service Manual Appendices 8-7 Appendix D: Glossary of Terms Abbreviations Abbreviation Meaning Analog to digital Automatic Gain Control Automatic level control Transducer Base - Emitter Binary-coded decimal Capacitor CMOS Complementary metal oxide semiconductor Central processing unit Cathode-ray oscilloscope Continuous wave;...

  • Page 78: D.2 Abbreviations Of Units

    8-8 Appendices X-2 Technical Service Manual Abbreviations (cont'd) Abbreviation Meaning Push-to-talk Power Quality factor Resistor Random Access Memory REF-PWR Reference-Power Radio frequency RFDS Royal Flying Doctor Service Root mean square Read Only Memory Receive; Receiver Switch Suppressed carrier frequency SINAD...

  • Page 79: D.3 Abbreviations Of Unit Multiples

    X-2 Technical Service Manual Appendices 8-9 Unit Multiples Abbreviation Prefix Numeric Meaning tera one million million giga one thousand million mega one million kilo one thousand hecto one hundred deca deci one tenth centi one hundreth milli one thousandth µ...
  • Page 98 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.
  • Page 99 Addendum 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 •...

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