Cumbria Designs User Manual
Contents
1. Cumbria Designs T 2 SSB IF Sub System User Manual 1 INTRODUCTION 2 2 PREPARATION 2 3 ASSEMBLY 2 4 CIRCUIT DESCRIPTION 4 5 ASSEMBLY 7 6 TESTING 9 Appendix A Component Overlay Appendix B Parts List Appendix C Circuit Diagram cumbria 16 Chestnut Close designs Culgaith PENRITH Cumbria CA10 1QX UK www cumbriadesigns co uk 1 Introduction Thank you for purchasing the Cumbria Designs T2 SSB IF sub system We hope that you enjoy constructing this kit and find many uses for this versatile design This manual describes the assembly and operation of the T2 Even if you are a seasoned constructor we respectfully ask that you first read this manual and familiarise yourself with the instructions and kit contents before commencing soldering If assembled carefully this unit will provide many years of reliable service The Cumbria Designs Team 2 Preparation 2 1 Unpacking The T 2 kit is a complicated project which comprises over 270 parts To reduce the risk of error or mislaid parts we suggest the following method of working e Keep all parts in a large clean container preferably a tin with a lid e When unpacking the anti static bags check very carefully to ensure that no parts are trapped in the corners of the bags e Resistors and diodes are generally supplied in bands Cut the component from the band only when you are ready to fit it to the board e Loose pins are provided for the h2. 12 100R Brown Black Black Black Brown R1 R2 R16 R18 R19 R21 R22 R26 R30 R40 R49 R54 5 220R Red Red Black Black Brown R5 R6 R7 R46 R47 470R Yellow Mauve Black Black Brown R42 R48 R50 16 1K Brown Black Black Brown Brown R8 R9 R11 R13 R20 R25 R27 R34 R36 R39 R41 R56 R59 R63 R64 R65 4 2K2 Red Red Black Brown Brown R12 R24 R44 R58 7 4K7 Yellow Mauve Black Brown Brown R10 R28 R29 R52 R53 R67 R68 10 10K Brown Black Black Red Brown R14 R15 R17 R31 R33 R35 R57 R60 R61 R66 5 100K Brown Black Black Orange Brown R38 R43 R45 R51 R62 2 150K Brown Green Black Orange Brown R37 R55 T 2 PCB1 0 Version 1 5 Page 7 of 16 Cumbria Designs 5 3 Inductors Inductor L1 is mounted horizontally as with the resistors Inductor L2 is mounted vertically by bending one lead over in line with the inductor body and inserting into PCB as shown on the silk screen overlay 1 47uH Yellow Mauve Black L1 1 15uH Brown Green Black L2 5 4 Diodes amp LED Polarity conscious parts The cathode is marked by a band on the diode body Ensure orientation matches the PCB silk screen All diodes are mounted horizontally Bend leads at 90 degrees and insert into PCB hold diode body flush against PCB and bend underside leads apart slight to hold the diode in place 4 BAV21 SILICON DIODE Red Glass Body D5 D6 D7 D8 4 5082 3081 PIN DIODE Black or Clear body
3. them from interfering with the transmit path operation Microphone Amplifier A simple non inverting amplifier similar in design to the receiver AF preamplifier is used to amplify the audio from the microphone input to drive the modulator A fairly large output swing of several volts is required to produce an RF output from the modulator that is high compared to the residual carrier Transmit Path IF Switch A 2N3906 Q1 and two PIN diodes form the IF bypass route for the transmit signal from the modulator On receive the PIN diodes isolate the transmit signal path from the IF amplifier On transmit the IF amplifier is muted and Q1 is powered causing the PIN diodes conduct to provide a signal path in the transmit direction Power Sequencing A simple circuit using two 2N7000 FETs Q2 Q3 ensures that during Tx Rx change over the unused supply rail is quickly discharged to allow a clean transition The unit requires the supplies 12v permanent 12v Rx and 12v Tx The Tx and Rx lines should be taken from a break before make relay to ensure that both lines are not simultaneously active Page 6 of 16 Cumbria Designs 5 Assembly The order of assembly is not particularly critical even though this is a relatively complicated circuit it is easier to test it in its complete state rather than to attempt to carry our individual stage testing as construction progresses The key to success is simply to ensure that the rig
4. 1 0 Version 1 5 Page 8 of 16 Cumbria Designs 5 8 Ceramic Dipped Capacitors These 2 54mm pitch capacitors have a yellow resin coating and are marked 100n 5 100nF CERAMIC DIPPED C28 C39 C48 C64 C65 5 9 Polystyrene Capacitor Insert into PCB and bend leads outwards slightly to hold in place whilst soldering 1 0 47uF POLY C21 5 10 Voltage Regulators Polarity conscious parts Two three terminal TO92 style regulators are used to supply the analogue switch and biasing voltage to the audio stages These are very similar in appearance to the transistors please take care not to mix them up 1 78L05 5V REGULATOR IC5 1 78L08 8V REGULATOR IC7 5 11 Transistors Polarity conscious parts Static sensitive parts Discharge yourself before handling Insert transistors so as to leave about 3mm of lead between the body and the board Solder centre lead check position and solder outside leads 5 2N3904 TRANSISTOR NPN Q6 Q7 Q12 Q17 Q18 2 2N3906 TRANSISTOR PNP Q1 Q15 6 J310 JFET Q4 Q5 Q9 Q10 Q11 Q13 5 2N7000 POWER MOSFET Q2 Q3 Q8 Q14 Q16 5 12 Variable Resistors Straighten the pre formed pins by gently compressing each pin with pointed nose pliers to remove the corrugations Align with holes and rake pins if necessary to allow body to clear adjacent parts Solder one pin check and adjust alignment if necessary and solder remaining two pins Note VR4 and VR6 are a close fit Rake pins to allow both pots to sit horiz
5. 4 43 cores as described below Trim the ends to fit the board Before insertion scrape the enamel away from the ends and tin with a hot iron Holding the iron on the exposed copper and applying solder will remove more enamel and tin the wire at the same time Primary and secondary windings go in direction of receive signal flow left to right See circuit diagram Transformers T2 to T4 Transformer Primary Secondary Orientation T2 4 turns 18 turns Primary facing M1 T3 16 turns 7 turns Primary facing Q5 T4 5 turns 17 turns Primary facing X6 Be sure to fit transformers with windings orientated correctly Ca and Cb Once T2 and T3 have been installed solder 68pF ceramics Ca and Cb as shown in Fig 2 Transformer T1 Transformer T1 is the most complicated to wind This carries the IF output winding 20 turns the modulator demodulator winding 6 turns bifilar and the transmit path link winding 2 turns The recommended assembly order is as follows IF Output Winding Take 30cm of enamelled copper wire and wind 20 turns onto an FT37 43 toroid Space the turns evenly around the toroid Trim the ends and tin Bifilar Winding a Take 20cm of enamelled copper wire and fold in half b Grip the open end of the in a small vice or similar to anchor it and the folded end in the chuck of a small hand drill c Apply gentle tension and keeping the bundle taut turn the hand drill to twist the bundle to around 5 twis
6. Bm to 10dBm The Assembled T 2 T 2 PCB1 0 Version 1 5 Page 14 of 16 Cumbria Designs T 2 Component Overlay J40 8 Op NIVWD A MLW S S ae 2 XL DAES 93 SR JET ENE CE Aue GT S3 393 al a i ese svig J9Y YJLJN S NIV AN O rey SSES FE aah Lit ebe SS 9 sro Jg EMA PHA Ge g 4n 09 subisspeuguns MAM a E WALSAS gr 8Ss cl OI CC SA ES 620 ZED Ek Appendix A Page 15 of 16 Version 1 5 Cumbria Designs T 2 PCB1 0 Appendix B Resistors 2R7 R23 R32 10R R3 R4 R1 R2 R16 R18 R19 R21 R22 R26 R30 R40 R49 R54 R5 R6 R7 R46 R47 R42 R48 R50 1K R8 R9 R11 R13 R20 R25 R27 R34 R36 R39 R41 R56 R63 R64 R65 R59 2K2 R12 R24 R44 R58 4K7 R10 R28 R29 R52 R53 R68 R67 10K R14 R15 R17 R31 R33 R35 R57 R60 R61 R66 100K R38 R43 R45 R51 R62 150K R37 R55 Trimpots 10K VR1 VR3 VR5 VRG 100K VR2 VR4 Capacitors 22pF C52 68pF C16 C17 C18 C19 C20 Ca Cb 100pF C37 C42 C46 C56 1n5 C47 10nF C1 C2 C4 C5 C6 C7 C9 C12 C13 C14 C15 C23 C24 C27 C29 C31 C32 C33 C34 C35 C36 C40 C41 C44 C45 C49 C50 C59 C62 100nF Dipped C28 C39 C48 C64 C65 0 47uF C21 10uF C8 C10 C11 C43 C51 C55 C60 C61 100uF C3 C22 C25 C26 C30 C54 C57 C58 Filter series capacitors mounted underneath PCB Trimmers 65pF VC1 VC2 Additional Parts Req
7. D1 D2 D3 D4 1 LED Bias LED Long Lead Anode facing IC2 LED 5 5 Crystal Filter This improved version of the Cohn filter requires series end capacitors to be installed between the filter and the matching transformers Two tracks between T3 and X1 and X6 and T4 are cut and bridged by 68pF ceramic capacitors Ca and Cb Cut the tracks before assembling the filter see Fig 2 below Do not fit Ca Cb at this stage O CG IL Cut o K AN Cut v o O O Fig 2 Track cuts and Ca Cb positions 5 6 Crystal Filter Heat sensitive parts When soldering do not apply excessive heat 8 crystals are supplied with the kit for the filter and USB LSB carrier oscillators The two carrier oscillator crystals are marked with indelible ink install these first in positions X7 and X8 of the carrier oscillator circuit order unimportant The 6 remaining crystals have been matched in frequency for use in the Cohn filter Install these in positions X1 to X6 of the filter section order unimportant 5 7 Ceramic Capacitors Insert leads into PCB such that the capacitor body is flush with the board surface Bend the leads outwards slightly to hold the capacitor in place during soldering 1 22pF CERAMIC C52 5 68pF CERAMIC C16 C17 C18 C19 C20 4 100pF CERAMIC C37 C42 C46 C56 1 nb CERAMIC C47 29 10nF CERAMIC C1 C2 C4 C5 C6 C7 C9 C12 C13 C14 C15 C23 C24 C27 C29 C31 C32 C33 C34 C35 C36 C40 C41 C44 C45 C49 C50 C59 C62 T 2 PCB
8. ODE plug select LSB operation Apply 12V to 12V and RX inputs of the PWR connector and check that the current is in the region of 200mA Disable the AGC input by shorting pins 1 and 2 of the AGC_OFF input Advance the AF gain until a faint hiss is heard With no IF Gain pot attached adjust the AGC bias pot VR3 for maximum IF noise this will be at an AGC voltage of about 8V If no noise is heard check that the carrier oscillator is functioning and that the right DC conditions have been applied to the USB LSB control input Select USB operation on the MODE connector Connect a 7dBm local oscillator source set to the desired receive frequency IF frequency to the LO port e g for 14 250MHz LO 14 250 11 059 3 191MHz or 14 250 11 059 25 309MHz with inverted sideband operation Connect an antenna or signal source and adjust the carrier oscillator by listening to the unwanted sideband suppression level Change over sideband oscillators and adjust USB carrier for good suppression and a similar passband sound to that of LSB operation Enable the AGC by removing the short on the AGC_OFF control and set AGC gain by adjusting VR5 Note that too much gain will cause the AGC to overshoot indicated by a characteristic pumping of audio level A smooth AGC operation across a wide range of receive signal levels should be obtained 6 3 SSB Transmit Set Up Reconfigure the supply inputs for transmit operation With a receiver loosely cou
9. aca SSS Seca Sel cece oS Slee SSS eco oan Scio oS Post TUF 3 Mixer Amplifier DC and Signal Switching Tx 12V Rx Fig 1 T 2 block diagram Amplifier LSB operation The PCB carries all DC switching circuitry for controlling signal flow during transmit and receive operation A detailed stage description follows Please refer to the circuit diagram given at the rear of this manual Mixer A TUF 3 mixer forms the front end Rather unconventionally the IF port of theTUF 3 is used as the RF input output port This allows operation down to a few 10s of kHz for experimentation at VLF The penalty for this increased flexibility is a slight in distortion products but so slight as to not be noticeable except with measurement equipment Bi Lateral Amplifer Two J310 JFETs introduce about 15dB of post mixer gain with a low noise figure The direction of amplification is selected by switching the 12v supply between either stage PIN diodes D3 and D4 isolate the unused amplifier The impedance matching into the amplifier is performed by transformers T1 and T2 which transform the 1K input impedance seen from either amplifier port into 50 Ohms for the mixer and 180 Ohms for by the filter Carrier Buffer 4053 Amplifier USB LSB Audio Stages Carrier Oscillators FK T 2 PCB1 0 Version 1 5 Page 4 of 16 Cumbria Designs SSB Filter A Minimum Loss six crystal 11 059HMz Cohn SSB filter p
10. eader connector shells During transit some of these may become lodged in the connectors Check and if necessary remove carefully e Choose a well lit work area with a light neutral covering e g white paper to help you spot dropped parts e Don t attempt to solder too many parts at once similarly limit your time spent soldering to a comfortable periods of T 2 PCB1 0 Version 1 5 say an hour taking breaks in between 2 2 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 Magnifier 3 Assembly The production of a successful finished working kit is dependent upon care during component handling placement and good soldering Don t be tempted to rush the construction 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 3 1 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 Page 2 of 16 Cumbria Designs 103 10nF etc Resist
11. hanically 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 T 2 PCB1 0 Version 1 5 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 to avoid contamination with grease or fingerprints 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
12. he output of the pre amplifier is muted by a FET switch Q8 A resistor and capacitor in the gate circuit delay the turn off time of the FET switch slightly preventing loud clicks or thumps on Tx Rx operation This simple circuit produces a nice soft change over action An LM380 8 is used as the audio power amplifier AGC System A full wave audio derived AGC system controls the IF gain The AGC circuit uses an NE5532 dual op amp to amplify the audio from the AF pre amplifier and produce two anti phase outputs to drive the AGC detector The detector comprises of two transistors that are alternately switched on on each half cycle of audio to discharge the AGC timing capacitor The attack time is set by series resistor R59 decay time by R55 the supply resistor to the timing capacitor C60 A 2N7000 Q16 in the collector circuit of the AGC detector allows the detector to be isolated from the AGC circuit disabling the AGC action T 2 PCB1 0 Version 1 5 There are two adjustments for the AGC system AGC gain set by VR5 AGC bias by VR3 The output from the AGC detector is buffered by Q15 an emitter follower from which the AGC line is taken to drive the IF stages and S Meter circuit The AGC action is very good and with the careful adjustment provides a good clean action with no clicks or popping On transmit the AGC line is grounded by a 2N7000 Q14 controlled by the Tx supply line This mutes the IF stages preventing
13. ht component is placed in each position Please check very carefully the value and orientation of each part before soldering In the words of the carpenter Measure twice cut once The following recommended assembly sequence is based upon part profile above the PCB and will allow parts to be held in place whilst the board turned over for soldering All components except ceramic capacitors Ca and Cb are mounted on the top silk screen side of the board You are strongly advised to check off each part number in the instructions as it is installed to keep a track of progress Trim off excess leads after soldering PRECAUTIONS Static sensitive components Discharge yourself to ground before handling Avoid wearing static generating clothing e g wool man made fibres etc during assembly D Critical step during installation such as orientation Read associated note 5 1 IC Sockets Ensure correct orientation Match index cut out on socket to board printing Tip solder one corner pin only then check positioning before continuing 4 DIL Socket 8 way IC1 IC2 IC4 IC6 1 DIL Socket 16 way IC3 5 2 Resistors All resistors are mounted horizontally Bend leads sharply to 90 degrees at each end of the body and insert into board Press resistor body firmly against PCB and bend leads apart slightly on underside of PCB to hold resistor in place 2 2R7 Red Mauve Black Gold Brown R23 R32 2 10R Brown Black Black Brown R3 R4
14. ive operation the mixer demodulates the IF output to audio and during transmit modulates the microphone audio into a Double Sideband Suppressed Carrier DSBSC signal The DSBSC signal is fed to the SSB filter by the IF bypass amplifier where the unwanted sideband is filtered out to produce an SSB signal at the IF frequency The mixer requires single phase square wave carrier signal to drive the switching action This is generated by the carrier oscillator section The two other switches of the 4053 are used to select the transmit and receive audio signal paths to and from the product detector modulator Page 5 of 16 Cumbria Designs Carrier Oscillator Dual JFET Colpitts oscillators generate the carrier signals for LSB and USB operation A bipolar buffer stage amplifies the carrier signal to a level suitable for driving the 4053 mixer Two identical crystals are used for LSB and USB operation An inductor L2 in series with the crystal of the USB oscillator X8 allows it to be pulled down in frequency on the lower side of the filter response for USB operation Carrier oscillator selection is made by switching the 8v regulated supply to either oscillator Receive Audio Stages A low noise pre amplifier and a power amplifier make up the receiver audio chain Both of these stages are permanently powered Most of the AF gain is provided by the AF pre amplifier an NE5534 op amp To reduce speaker noise during transmit t
15. joint remove the old solder with a solder sucker and re solder Mistakes do happen Should you inadvertently solder a part in the wrong position we recommend that you DO NOT attempt to remove it intact To prevent damage to the PCB through excessive heating and mechanical strain the wrongly placed part should be cut off the board Page 3 of 16 Cumbria Designs leaving it s leads pins exposed These can then be removed individually and the PCB pads de soldered and prepared for the replacement part 4 Circuit Description 4 1 General The Cumbria Designs T2 is designed to serve as the core of a single conversion SSB transceiver for operation from a few kHz to 400MHz A simplified block diagram of the T1 is shown in Fig1 The signal path uses bilateral circuitry allowing several of the main circuit elements to be used during both transmit and receive The RF port is common to transmit and receive signals A two stage hybrid cascode IF amplifier provide the IF gain which is controlled by a full wave audio derived AGC system Control functions are included to disable AGC and apply manual IF gain control A CMOS bi lateral switch performs the product detector modulator and audio path switching functions Low noise operational amplifiers are used in the AF stages the AF power amplifier output is in the order of 500mW Two carrier oscillators provide Upper Sideband USB and Lower Sideband Eerst erer dE Ste SSeS eS Seca a SS
16. ment Transmit Path Link Winding T 2 PCB1 0 Version 1 5 Page 11 of 16 Cumbria Designs This is best installed once the T1 has been mounted onto the PCB Fit the two turn transmit path winding using 10cm of wire to form a double turn on the lower part of the toroid near to the Transmit Path Link Winding pads Trim the ends of the winding leaving enough wire to pass through the pads clean the ends tin and solder in place 5 19 Connector Assemblies Connector shells and pins are supplied to allow connection of power audio and controls to the T 1 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 Each connector assembly comprise of two component parts 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 o
17. nce IF Amplifier A two stage hybrid cascode amplifier provides the IF gain In the hybrid configuration a JFET and a bipolar transistor are used to form a cascode pair All of the benefits of the cascode are retained high gain stability and low noise but with a T 2 PCB1 0 Version 1 5 bipolar transistor as the gain control element the biasing conditions offer the additional advantage of a much larger gain control range A further advantage of this configuration is that gain control and stage gain are preserved at much lower supply voltages than with the dual FET cascode The common reference for the IF stages is lifted a couple of volts above ground by an LED This allows the AGC voltage to go negative with respect to the IF stages increasing AGC range and ultimate attenuation The Led provides a useful diagnostic indication of amplifier current The IF amplifier gain is around 45dB with an AGC range in excess of 100dB IF muting on transmit is provided by FET Q14 which grounds the AGC line Product Detector Modulator The product detector modulator employs a single switch of a 4053 CMOS bi lateral switch in conjunction with T4 to form a single balanced mixer Fixed mid rail DC bias is applied to the transformer side and an adjustable bias for balancing the mixer to the audio side The bias voltage is adjusted to null the current flowing through the switches which in turn produces a carrier null During rece
18. ontally 4 10K CERMET VR1 VR3 VR5 VR6 2 100K CERMET VR2 VR4 5 13 Variable Capacitors 2 65pF TRIMCAP VC1 VC2 5 14 Electrolytic Capacitors Polarity conscious Parts The short lead marked goes to ground 8 10uF ELECTROLYTIC C8 C10 C11 C43 C51 C55 C60 C61 8 100uF ELECTROLYTIC C3 C22 C25 C26 C30 C54 C57 C58 5 15 Connectors a Headers Recommended Header Connector orientation is as marked on the PCB with rear locking tab facing into the centre of the board 4 Header 2 way AGC LS MIC S MTR 3 Header 3 way AF_GAIN IF_GAIN MODE 1 Header 4 way PWR b SMB Sockets Insert socket into PCB and solder centre pin to secure Check connector sits square adjust if necessary and solder remaining pins 2 SMB Socket LO RF T 2 PCB1 0 Version 1 5 Page 9 of 16 Cumbria Designs 5 16 DIL Integrated circuits Static sensitive parts Discharge yourself to ground before handling Orientation critical Form IC pins correct alignment before insertion into sockets by placing the device on its side on a flat firm surface and gently rotate the body downwards against its pins 2 NE5534N OP AMP IC1 IC2 1 LM380N 8 AF POWR AMP IC4 1 NE5532N DUAL OP AMP IC6 1 74HC4053 ANALOGUE SWITCH IC3 5 17 Packaged Mixer Static sensitive part Discharge yourself to ground before handling Fit TUF 3 Mixer in positions M1 taking care to observe marked orientation 5 18 Transformers Wind the four transformers T1 T4 onto FT3
19. ors have their values represented by coloured bands the latter 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 3 2 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 component leads is easily done with a pair of pointed nose pliers and using the hole spacing on the PCB as a measure Alternatively small formers made from scrap off cuts of Vero board etc make ideal templates that produce consistent results Some parts such as the 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 3 3 Soldering Before applying solder check carefully that the component you have placed is in the right position The T 2 uses a through plated double sided printed circuit board PCB 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 mec
20. pled to the RF port of the T 2 it should now be possible to detect the carrier output Adjust VR1 carrier balance for minimum signal Note that in close proximity with unscreened connections the receiver will also detect a directly radiated carrier from the oscillator circuit making a true assessment of suppression impossible Adjust coupling to minimise this Connect a low impedance microphone to the MIC connector and adjust VR2 the microphone gain for a clean SSB signal An oscilloscope of suitable bandwidth connected to the RF port should show a peak to peak output of approximately 150mV across 50 Ohms T 2 PCB1 0 Version 1 5 Page 13 of 16 Cumbria Designs Now revisit the carrier oscillator tuning As a rough guide aim to have the carrier oscillators sitting around 20dB down the filter skirt There will be some asymmetry due to the ladder filter By re adjusting the carrier oscillator frequencies trimming the carrier balance and setting the microphone gain correctly good suppression will be achieved together with a good audio passband The T2 is now ready for use 6 4 Need Help Hit a problem that you can t resolve Don t worry we re here to help Contact us by letter or email at support cumbriadesigns co uk for support Typical T 2 Application Rx Switch Sg LS 8 Ohms Se Sr Cumbria Designs T 2 Mic LO LPF PA Strip AF Gain Local IF Gain Oscillator Controls F Rx Freq IF Frequency P 7d
21. rientated to the face of the shell with 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 some pointed nose pliers The pin will be released and can be pulled out of the shell AF_GAIN IF GAIN Locking Tab z j 7 Gnd Out Gnd 12V Break Before Make AF Gain Pot IF Gain Pot Front Front a D Ny Z AGC Off Sideband Select S Meter Fig 5 Connector Wiring Assembly complete well done Now carefully check your work for dry joints and bridges before moving on to testing T 2 PCB1 0 Version 1 5 Page 12 of 16 Cumbria Designs 6 TESTING The testing sequence assumes that the filter and carrier crystals have been have been installed A log 10K AF gain pot speaker microphone and sideband select switch will be required for basic testing A linear 10K IF gain pot and S Meter 100uA 200uA will allow full testing and set up 6 1 DC Tests Before connecting the T 2 to your power supply for the first time carry out these simple checks just to be safe e With a meter set to resistance or continuity check the PWR supply connector on the main PCB for shorts or very low resistance Check each supply input against ground e Check the polarity of your supply and ensure that the PWR plug is wired correctly 6 2 Receive Set Up With a switch or wire link connected to the M
22. rovides excellent selectivity and stop band attenuation The filter bandwidth is approximately 2 3kHz All crystals have been matched in frequency to ensure reproducibility The two carrier crystals are marked with indelible ink These must not be used in the filter If you wish to adjust the filter bandwidth increasing the terminating impedance and reducing the capacitor values will increase bandwidth the converse will reduce bandwidth Other types of ladder filter such as the Butterworth or Chebychev may also be used with the existing crystals by using different capacitor values and terminating impedances We recommend that you breadboard your filter off the main PCB before installing the final parts values Due to the slight asymmetry of the SSB ladder filter the USB LSB passbands may sound slightly different This has little or no impact upon performance An alternative to selecting sideband by carrier oscillator is to shift the Local Oscillator LO frequency With modern DDS devices this is trivial If this approach is to be used we recommend operating the IF in LSB mode to take advantage of the better opposite sideband suppression offered by the asymmetry If desired the filter parts may be completely omitted from the PCB and a commercial crystal lattice filter installed If you decide to use a different filter to that included with this kit ensure that you adjust T3 and T4 to provide the correct terminating impeda
23. ts per cm Remove from the drill and vice d Wind the twisted bundle over the IF output winding to give 6 turns e Trim each end of the bundle cutting off the fold to form two separate conductors Leave at least 1 5cm free Tin the ends f Using a meter in resistance or continuity mode identify the start and finish of each conductor and combine as shown T 2 PCB1 0 Version 1 5 Page 10 of 16 Cumbria Designs g Insert the transformer winding ends into the PCB taking great care to ensure that all windings are matched to the correct pads tension gently to hold the core in place and solder a Fold 20cm length of 10cm wire in half c Twist with hand drill N gt lt Ai B1 f Use a meter to identify each winding as A and B Treat each end as 1 and 2 A1 A2 A2 B2 A1 B1 f contd Connect ends B1 and A2 as shown to produce a bifilar centre tapped winding A2 B2 CT Fig 3 T1 bifilar winding A1 CT detail Mounting T1 Insert the leads into the T1 PCB pads as shown The orientation of the IF output and bifilar A1 B2 ends is not important Be sure to make the centre tap CT using B1 and A2 ensure that the centre tap pair is inserted into the CT pad shown below Transmit C12 R20 path link winding a el 19 en CT Bifilar Gen TT E atiB2 Order winding 6b IF Output gt not important winding gt 20t wk fox Fig 4 Transformer T1 place
24. uired for operation AF Gain 10K Log IF Gain 10K Lin Speaker 8 Ohm 2W Microphone Low Impedance dynamic T 2 PCB1 0 T 1 PCB VERSION 1 0 PARTS LIST Inductors 47uH 15uH L1 L2 Semiconductors 2N3906 2N3904 2N7000 J310 Q13 78L05 78L08 5082 3081 BAV21 LED5MM 74HC4053 LM380N 8 NE5532N NE5534N Mixer TUF 3 Connectors SMB Sockets Header 2 way Header 3 way Header 4 way Crimp Pins Toroid Cores T37 43 Crystals 11 0592MHz Misc Copper Wire T2 PCB Version 1 5 Cumbria Designs Q1 Q15 Q6 Q7 Q12 Q17 Q18 Q2 Q3 Q8 Q14 Q16 Q4 Q5 Q9 Q10 Q11 IC5 IC7 D1 D2 D3 D4 D5 D6 D7 D8 LED IC3 IC4 IC6 IC1 IC2 M1 LO RF JP2 JP4 JP6 JP8 JP3 JP5 JP7 JP1 21 T1 T2 T3 T4 X1 X2 X3 X4 X5 X6 X7 X8 1m With switch for transceiver power on off With optional switch for AGC on off Page 16 of 16
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