X-Lock 3 - Cumbria Designs
Contents
1. 3 PCB 3 0 Doc Rev1 2 Page 6 of 14 Cumbria Designs pushed inwards by placing the device on its side on a firm surface and gently pressing the body down against the pins When inserting parts take care to check orientation and pin alignment Fit IC3 PIC16F628A Processor 18 pin DIL Fit IC4 ACPL827 A 827 Dual opto coupler 8 pin DIL Fit IC5 MC33201 Operational Amplifier 8 pin DIL 4 12 Connector Assemblies Connector shells and pins are supplied to allow connection of power and signal lines to the X Lock The use of good quality colour coded heat resistant multi stranded wire is recommended To avoid accidents a colour code convention should be chosen to represent function e g Red ve supply Black ground striped colours controls etc The connector assemblies comprise of two components the shell and the pins To terminate a conductor first strip back about 2mm of insulation and tin the exposed wire Place the tinned end of the wire into a pin such that the tinned wire sits inside the inner pair of tabs and the insulation sits within the outer tabs With small pointed nose pliers carefully compress the outer tabs onto the insulation to hold the wire Repeat this with the inner tabs to grip the exposed conductor Very carefully solder the exposed conductor in place taking care not to allow solder to flow onto the locking tab Finally insert the pin into the shell with the small locking tab orientated to the face of the shell w2. The rate of change of the control voltage is set by the correction pulse width and the R9 C11 and C15 time constant The correction rate may be adjusted by changing the basic correction pulse width there are 8 settings ranging from 10uSec doubling on each step to a maximum of 1 28mSec The factory setting X Lock 3 PCB 3 0 Doc Rev1 2 Page 9 of 14 Cumbria Designs is the maximum 1 28mSec Whilst this will ensure quick and effective locking it may be too severe for some VFOs resulting in a noticeable warble on received signals The pulse width is adjusted as follows a With the X Lock operating and locked LED green press SW2 If this is the first change or the adjustment is at one of the end limits the LED will change to red If the current setting is somewhere in between the LED will extinguish b Press SW1 to reduce the pulse width or SW2 to increase the pulse width Each step change is marked by the LED flashing amber When either end limit is reached the LED will change to red c By allowing the X Lock to settle between changes the effect of the new pulse setting may be monitored The optimum value will provide good stabilisation with no warble caused by correction signal changes To save the new setting press and release SW1 and SW2 simultaneously The LED will flash green indicating that the setting has been saved and normal operation will resume The new setting will be loaded each time the X Lock is
3. IC Sockets Ensure correct orientation Match index cut out on socket to board printing Tip solder one pin only then check positioning before continuing Heat solder and reposition if necessary a Fit the 18 pin microcontroller socket for IC3 b Fit 8 pin sockets for IC4 IC5 4 3 Crystal Fit X1 the 20MHz crystal This is heat sensitive and is easily damaged if overheated It is recommended that a gap of about 2mm is left between the crystal and the PCB This will provide a little extra thermal isolation during soldering 4 4 Ceramic Capacitors Suggested Installation order 22pF C5 C6 22J 10nF C2 C8 C9 C12 C13 C15 C16 103 100nF C7 104 4 5 Transistors and Diode Polarity conscious components Ensure correct orientation The 2N5485 and 2N7000 are Static sensitive parts Discharge yourself to ground before handling Avoid wearing static generating clothing e g wool man made fibres etc during assembly a Fit JFET Q1 2N5485 b Fit Bipolar transistor Q2 MPSH 10 c Fit FET Q3 2N7000 X Lock 3 PCB 3 0 Doc Rev1 2 Page 5 of 14 Cumbria Designs D d Install D1 BAV21 4 6 Regulators Es Polarity conscious components Ensure correct orientation When installing the two T092 Voltage regulators ensure that their orientation matches that shown on the silk screen a Fit 8V regulator ICT 78L08 b Fit 5V regulator IC2 78L05 4 7 Tactile Switches Insert and solder the two 7mm tactile switches into positions SW1
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5. X Lock VFO Stabiliser User Manual CONTENTS 1 INTRODUCTION 2 2 PREPARATION 2 3 CIRCUIT DESCRIPTION 3 4 ASSEMBLY 5 5 TESTING 7 6 CONFIGURATION AND SET UP 8 APPENDIX A Troubleshooting cumbria 16 Chestnut Close designs Culgaith PENRITH Cumbria CA10 1QX UK www cumbriadesigns co uk 1 Introduction Thank you for purchasing the Cumbria Designs X Lock kit We hope that you enjoy constructing this kit and find many uses for this feature rich design This manual describes the assembly and operation of the X Lock kit even if you are a seasoned constructor we respectfully ask that you read this manual and familiarise yourself with the instructions and kit contents before commencing construction If assembled carefully this unit will provide many years of reliable service The Cumbria Designs Team 2 Preparation 2 1 Tools We recommend that the following tools are used during assembly and testing 25W fine tipped soldering 60 40 Rosin cored solder 5 or smaller diagonal side cutters Small pointed nosed pliers Solder sucker just in case Multimeter 2 2 Conventions The following symbols are used within the assembly instructions to draw attention to critical steps such as component orientation and anti static precautions The associated narrative describes the action required D Critical Step Static Sensitive 2 3 Assembly The production of a successful finished working kit is dependent upon
6. and SW2 The pin spacing ensures that the switches can only be fitted in one plane Press each switch into place gently once inserted the corrugated pins will hold the switch in place for soldering 4 8 Electrolytic Capacitors D Polarised Capacitors observe the polarity shown by the silk screen 10uF C1 C3 C4 C11 100uF C10 C14 4 9 Connectors Recommended Pin Header Connector orientation is with rear locking tab facing into the centre of the board A three way header is provided for the LED to allow it to be remotely fited to a front panel if required a Fit the 4 two pin headers PWR RF T R VAR b If you wish to extend the Tri Colour LED fit the three way LED header 4 10 Status LED The Tri colour LED has three leads The centre lead is the cathode and the two outer leads are anodes for the red and green LEDs The shorter of the outer leads is the red LED anode The Tri colour LED is connected with the short lead red anode nearest the crystal X1 The LED may be mounted directly on the PCB or connected via the supplied three way header if remote viewing is required 4 11 Semiconductors Static sensitive parts Discharge yourself to ground before handling Avoid wearing static generating clothing e g wool man made fibres etc during assembly Orientation is critical Observe correct alignment of IC pins which will need to be gently formed for correct alignment before insertion into sockets IC pins can be X Lock
7. ay Shell 2 Way Pin Header 2 Way Shells Crimp Pins 18 Pin DIL Socket 8 Pin DIL Sockets Tactile Switches PWR RF T R VAR NN P P ER S1 S2 PCB X Lock v3 0 External VFO Parts 1 1N4004 Diode 1 100K Resistor 1 22pF Ceramic Capacitor 1 68pF Ceramic Capacitor 1 10nF Ceramic Capacitor m Z e X Lock 3 PCB 3 0 Doc Rev1 2 Cumbria Designs Page 14 of 14
8. careful component handling careful placement and good soldering X Lock 3 PCB 3 0 Doc Rev1 2 Don t be tempted to rush the construction even though this is a relatively simple kit a wrongly placed component can provide hours of frustrating fault finding Also as this kit uses a double sided Printed Circuit Board PCB with through plating removal of a wrongly soldered part can be difficult Follow the assembly instructions carefully to avoid mistakes 2 4 Component Identification All parts carry a coded identity to describe their values It is important to be able to recognise these during assembly Capacitors have their value printed numerically e g 104 100nF 103 10nF etc Resistors have their values represented by coloured bands this is a frequent source of confusion To simplify component identification the parts list carries the identities of each component as it appears on the device For resistors the colour coding is given This should be referred to during assembly to ensure the right parts are placed in their respective positions on the PCB 2 5 Component Leads Many of the passive components will require their leads to be formed to align with the holes on the PCB This mainly applies to the axial parts such as resistors and diodes Forming Page 2 of 14 Cumbria Designs component leads is easily done with a pair of pointed nose pliers and using the hole spacing on the PCB as a measur
9. e Alternatively small formers made from scrap off cuts of Vero board etc make ideal templates that produce consistent results Some parts such as variable resistors have preformed leads designed for machine assembly These will require straightening to align with the board layout Again a pair of pointed nose pliers should be used to carefully flatten the factory performing to produce straight leads 2 6 Soldering Before applying solder check carefully that the component you have placed is in the right position This is a through plated double sided board Whilst some of the pads are very small the area presented by the through plating is more than adequate to allow good solder flow to form mechanically strong good electrical joints These can be difficult to undo please double check The majority of problems are likely to be caused by soldering faults These can sometimes be difficult to find Here are some basic golden rules that will help you to avoid poor solder joints e Clean Iron Make sure your soldering iron tip is in good condition and tinned A small moistened pad for cleaning tips regularly used to wipe off excess solder and flux will ensure that your iron performs well Remember to tin the iron immediately after each wipe e Clean Leads and Pads All of the component leads and PCB pads in this kit are pre tinned and should not need cleaning before soldering Please ensure that parts are handled so as
10. e stages and offers a wide operating range for the control voltage reducing the possibility of loop saturation 1N4004 power diode 100K resistor 22pF and 68pF capacitors are included with the X Lock kit These are intended to be configured as a varactor correction circuit shown in fig 1 This circuit should be suitable for most applications up to about 15MHz Above this frequency the value of the coupling capacitor may need to be reduced considerably to prevent over correction An alternative to using an additional correction circuit is to merge the correction signal with an existing RIT line More information on this together with specific examples are available on the Cumbria Designs website www cumbriadesigns co uk Page 4 of 14 Cumbria Designs 4 Assembly The following assembly sequence is recommended This allows most of the smaller parts to be held in place with the board turned over whilst soldering the underside All components are mounted on the top silk screen side of the board 4 1 Fixed Resistors Broad tolerance band shown in capitals 100R R2 R4 Brown Black Black BROWN 390R R5 R10 R11 R13 Orange White Black Black BROWN 470R R1 R6 R14 Yellow Mauve Black Black BROWN 1K R3 Brown Black Brown BROWN 10K R8 Brown Black Black Red BROWN 100K R9 Brown Black Black Orange BROWN 390K R7 Orange White Black Orange BROWN 2M2 R12 Red Red Black Yellow BROWN 4 2
11. ifting greater than LED flickers RED GREEN 50Hz second Normal during VFO initial Received signals sound clean warm up Check varactor circuit installed correctly check control voltage present at varactor circuit input Power Power applied but unit doesn t Check Power Supply polarity work Little or no current drawn Check 12V on inputs to Regulators Check Regulator Ground continuity Poor or No LED goes through initialisation Check 8V regulator for input and output Lock sequence but there is no control confirm correct orientation voltage output Are IC4 and IC5 inserted correctly Check soldering of IC4 and ICS pins LED shows initialisation Check correction circuit shifts VFO successful but VFO is not frequency by applying DC voltage Check stabilised diode orientation and coupling into VFO VFO sounds clean but still drifts VFO not stable enough Check design LED Flickers Red Green Increase correction rate Increase correction varactor coupling into VFO Over X Lock LED shows lock and Reduce correction rate Decrease Correction VFO is stable but warbling correction varactor coupling into VFO evident on received signals VFO jitters causing warbling Varactor is over compensating pulling VFO modulation on received signals out of lock range Reduce correction LED Flickers GREEN RED varactor coupling into VFO X Lock 3 PCB 3 0 Doc Rev1 2 Page 11 of 14 Cumbria Designs X Lock Schematic d l d l
12. ith the small cut outs Push home until the locking tab snaps into the cut out Should you need to remove a pin gently press the locking tab in with a small screwdriver or the end of a pair of pointed nose pliers The pin will be released and can be pulled out of the shell Assembly complete well done Now carefully check your work for dry joints and bridges before moving on to testing 5 TESTING Before connecting the X Lock to your power supply for the first time carry out these simple checks just to be safe 5 1 Basic Electrical Tests 5 1 1 12 Volt Input With a multimeter set to resistance place the Red meter lead onto 12v and the Black to Ground and check for a high resistance Note that due to C11 charging the reading will show change providing there is not a short circuit then all is well 5 1 2 5 and 8 Volt Rails Carry out the resistance test on the output side of the regulators IC1 and IC2 to check the integrity of the regulated rails Due to the circuitry of the X Lock a much lower resistance will be measured the reading will depend upon the characteristics of the multi meter but typically should be around 250 Ohms X Lock 3 PCB 3 0 Doc Rev1 2 Page 7 of 14 Cumbria Designs 5 2 Powering Up 5 2 1 Power With no controls set connect a 12 volt supply to the X Lock Double check the polarity take a deep breath and switch on The status LED will sequence through Red Amber and Green and then flash Red on a
13. me constant of the loop filter is very long resulting in a slow rate of change of the control voltage To ensure that the control voltage starts at centre rail a reset switch formed by FET Q3 is enabled by the processor on power on This ensures that C11 and C15 are fully discharged Once Q3 is turned off the capacitors re charge via R5 to set a centre rail output voltage In the unlikely event that the loop control voltage becomes saturated after a prolonged period of operation the X Lock 3 PCB 3 0 Doc Rev1 2 control voltage can be set to centre again by briefly powering the X Lock on and off to operate the Q3 reset switch The host VFO will need to be retuned following a reset A rail to rail operational amplifier IC5 buffers the filter providing a low impedance source for the control voltage to drive the external compensation varactor Whilst the varactor circuit exhibits a very high input impedance at DC the low impedance of the operational amplifier output stage reduces the effects of stray voltages on the control voltage line A simple RC filter R10 and C16 decouples the control signal at the point where it leaves the X Lock PCB There are two voltage regulators on the X Lock PCB IC2 provides the 5V supply for the 16F628 and the input amplifier IC1 provides 8V supply for the loop filter and output amplifier The use of separate regulated supplies provides good isolation between the digital and analogu
14. nd off indicating that there is no signal input 5 2 2 RF Checks Connect a signal source of around 500mV peak to peak or greater between the RF input pin and ground the status LED should stop flashing Red If it doesn t check the connection to the oscillator and the signal level At higher frequencies more drive may be necessary If the signal source is stable enough the LED may illuminate Green indicating that the drift rate between measurements is low This concludes the unit testing 6 CONFIGURATION AND SET UP 6 1 Installation Install the X Lock as close as possible to the VFO that it will work with Keep all signal leads as short as possible to minimise any unwanted radiation or pick up The X Lock requires a smoothed DC supply in the range 10V to 16V supply voltages greater than 16V should be avoided to prevent over heating of the regulators 6 2 Connection to a VFO 6 2 1 X Lock RF Input The RF input should be taken from the output of the buffer stage to avoid loading the VFO This will typically be a low to medium impedance source which should be capable to developing 500mV peak to peak or greater across the X Lock RF input without the loading presented by the X Lock significantly reducing the signal level 6 2 2 Correction Circuit The control voltage output VAR of the X Lock is used to drive a varactor in the VFO tuned circuit A 1N4004 diode 100K resistor 10nF and 68pF and 22pF capacitors are included in
15. powered on 6 5 1 Post Tuning Delay During VFO tuning the X Lock will halt correction and hold the control voltage at the current value The status LED will turn red indicating an unlocked state Once tuning is stopped the X Lock will wait for a period set by the Post Tuning Delay PTD before re applying lock This allows time for slow or fine manual tuning adjustments to be completed without the X Lock attempting to compensate for what it may see as drift 6 5 1 1 Changing the Post Tuning Delay The factory default PTD is set at 2 seconds this may be changed to settings of 1 to 15 seconds in 1 second steps The PTD is changed as follows a With the X Lock powered up press SW1 The status LED will extinguish indicating that set Up Mode has been entered b Change the PTD by pressing and holding SW1 to reduce the PTD or SW2 to increase the PTD The status LED will flash amber once every second change Once the lower limit of 1 second or the upper limit of 15 seconds is reached the status LED will flash red c To save the new PTD setting simultaneously press SW1 and SW2 The LED will flash green acknowledging the change The new delay setting is now active and will be applied on each subsequent power on 6 5 2 RIT Mode The X Lock has two Receiver Incremental Tuning RIT modes automatic and external RIT control 6 5 2 1 Automatic RIT An innovative feature of the X Lock is its ability to detect and respond to the rapid fre
16. quency changes associated with RIT operation in a transceiver In automatic mode the X Lock identifies and memorises the two frequencies use for RIT and uses them for locking the VFO after each RIT transition Under most circumstances automatic mode will be the best RIT option X Lock 3 PCB 3 0 Doc Rev1 2 Page 10 of 14 Cumbria Designs 6 5 2 2 External RIT Where it is desired to link the X Lock into the host transceivers RIT control system and external RIT control input is provided The signal driving this input must be conditioned as follows 3V to 20Vmax OV to 2V a Receive b Transmit Under no circumstances should the control voltage exceed these limits or fall below 0 7V or damage to the processor may result 6 5 2 3 Changing RIT Mode The factory setting is automatic mode the RIT mode is changed as flows a With the X Lock powered off press and hold down SW1 for Automatic RIT mode or SW2 for External RIT mode b Power on the X Lock The green LED will flash to acknowledge the change Release the button and normal start up will resume The new setting will be loaded each time the X Lock is switch on Appendix A Troubleshooting The following checks may help in identifying the cause of operational problems Area Symptoms Actions LED LED regularly flashes RED Input level too low or absent check connection to VFO and drive level LED permanently RED or Input OK but VFO dr
17. tches allow the key parameters to be adjusted after installation A tri colour LED indicates operational and diagnostic status Page 3 of 14 Cumbria Designs 3 2 Theory of Operation The Cumbria Designs X Lock is a derivative of the Huff Puff stabiliser system devised by the late Klaas Spaargaren PAOKSB in the 1970 s The x Lock compares the frequency of the controlled oscillator with a crystal reference hence X Lock Xtal lock to produce a correction signal which is used adjust the frequency of the oscillator The action is to hold the frequency of the controlled oscillator frequency at 10Hz lock points At the heart of the X Lock is a 16F628 processor IC3 which performs all of the measurement and control operations The input signal is buffered by Q1 and amplified by Q2 before being presented to the input of the processor on pin 12 The gate circuit is internal to the processor and operates over a 100mSec period to provide a count resolution of 10Hz The value of each measurement is compared with that of the previous and if the difference is equal to or less than 50Hz the 16F628 processor will generate a correction signal This takes the form of variable duration control pulses on the Up and Down signal lines from the processor to drive LED s within the opto coupler IC4 The opto coupler transistors are operated by the LEDs to charge or discharge the voltage stored in the loop filter R9 C11 and C15 The ti
18. than 5v p p Fig 1 VFO Connection 6 3 Using the RIT Line for Correction Many X Lock users have successfully coupled the VAR correction voltage into the transceiver RIT line Various approaches have been used from simple resistive summing to more complicated Op Amp summing circuits More information on this together with details of installations made by our customers is available on our website 6 4 Operation with a VFO With the X Lock is connected to a VFO the operating parameters may be changed to optimise performance and suit personal preferences 6 4 1 Initialisation On switch on the X Lock will run through an initialisation check indicated by the red amber green phase of the tri colour status LED and then commence measurement the host VFO frequency Once the VFO switch on drift has fallen below 50Hz sec the X Lock will apply correction control signified by the status LED changing from red to green When stabilisation has been achieved the LED will remain green Depending upon the VFO warm up characteristics the coupling of the correction circuit and the chosen correction rate lock may be intermittent during the first minute or two of operation 6 5 Set Up Mode The operating parameters of the X Lock can be changed to optimise performance or customise operation with a particular VFO Set Up mode allows three parameters to be changed a Correction rate b Post Tuning Delay c RIT Mode 6 5 1 Changing the Correction Rate
19. the kit to form the varactor circuit Whilst the 68pF or 22pF capacitors should be satisfactory for many applications it may be necessary to reduce this value significantly particularly for high VFO frequencies or where the capacitor is connected directly across the VFO tuned circuit In these instances the frequency control range may be excessive resulting in poor lock or high levels of ripple For best results it is recommended that the coupling capacitor value is chosen to give around 20kHz of frequency change for a control voltage range of Ov to 12v Test the varactor control range without the X Lock connected Alternatively it may be possible to find a connection point in the VFO circuit where either the 22pF or 68pF capacitor will give a satisfactory tuning range This might be an existing tap on the inductor or across the lower feedback capacitor in the case of a Colpitts oscillator X Lock 3 PCB 3 0 Doc Rev1 2 Page 8 of 14 Cumbria Designs The circuit configuration f Coupling is shown in Fig 1 all Capacitor o VFO tuned component leads on the See Text circuit VFO side of the 100K Control Voltage resistor should be kept from X Lock as short as possible to VAR 40nF EE GREEN offer best mechanical sel stability Be careful to z E confirm that the voltages Cathode Control Voltage Anode Ground at the point of d connection in the VFO ms 1N4004 do not exceed 50v DC K The AC component should be no greater
20. to avoid contamination with grease or fingerprints X Lock 3 PCB 3 0 Doc Rev1 2 e Soldering This is the bit that can trip up even experienced constructors For the solder to fuse with the surfaces to be joined it is necessary for them to be hot but not so hot as to damage the parts It s a simple as 1 2 3 1 Place the tip of the iron against the joint hold it there briefly to bring the metal surfaces up to temperature 2 Apply the solder allowing it to flow smoothly onto the surfaces 3 Remove the iron and inspect the new joint The finished joint should have a smooth shiny coating of solder If the joint is dull grey or has formed a spherical blob apply the iron to the joint remove the old solder with a solder sucker and re solder 3 Circuit Description 3 1 General The X Lock is a micro controller based frequency stabiliser designed as an easily applied add on to enhance the frequency stability of existing free running variable frequency oscillators VFOs This compact module will accept an input signal with a range of a few tens of kHz to over 50MHz and produce a variable correction voltage to drive a simple drift compensation circuit fitted to the host oscillator To minimise the risk of introducing digital noise to the host oscillator the analogue section of the X Lock operates from its own regulated supply and is optically coupled to the digital control circuitry Two tactile swi
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