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QRP Labs QCX 5W CW Assembly Instructions Manual

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QCX CW Transceiver
QCX 5W CW Transceiver kit assembly instructions
The "QCX": a single band, high performance 5W CW
Transceiver with built-in alignment and test equipment,
iambic keyer, WSPR beacon mode, and more...
Designed and produced by QRP Labs, 2017
(pictured with Palm Radio pico paddle http://palm-radio.de/english/eppaddle.html)
1
QCX assembly Rev 1.08

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Summary of Contents for QRP Labs QCX 5W CW

  • Page 1 QCX CW Transceiver QCX 5W CW Transceiver kit assembly instructions The “QCX”: a single band, high performance 5W CW Transceiver with built-in alignment and test equipment, iambic keyer, WSPR beacon mode, and more... Designed and produced by QRP Labs, 2017 (pictured with Palm Radio pico paddle http://palm-radio.de/english/eppaddle.html)

  • Page 2: Table Of Contents

    Contents Introduction ................................5 Parts list ..................................6 Assembly ................................... 7 Inventory parts ..............................13 Install IC2 socket ............................. 14 Install DIP integrated circuits IC3, IC5-10 ......................14 Install all 100nF (0.1uF) capacitors ......................... 15 Install all 470nF capacitors ..........................16 Install all 1nF capacitors ..........................
  • Page 3 3.46 Install 4-pin GPS header ..........................42 3.47 Install 3-pin DVM/RF detector header ......................42 3.48 Install 1-pin test points ........................... 43 3.49 Install power connector ..........................43 3.50 Install 7805 voltage regulator IC11 ......................... 44 3.51 Install pin headers for the LCD module......................44 3.52 Wind and install toroid L4 ..........................
  • Page 4 4.26 Alignment menu .............................. 96 4.27 Test equipment ............................. 100 Circuit design ................................. 104 Block diagram and summary ......................... 104 Circuit diagram .............................. 106 Synthesised oscillator............................ 106 Transmit/Receive switch ..........................107 Band Pass, Phase Splitter, QSD and pre-amps ....................108 90-degree audio phase shift .........................

  • Page 5: Introduction

    Thank you for purchasing this high performance single-band 5W CW transceiver kit, the QCX (for QRP Labs CW Xcvr). This kit has a long list of features! • Easy to build, single-board design, 10 x 8cm, all controls are board-mounted •...

  • Page 6: Parts List

    2. Parts list Resistors (all fixed resistors are ¼-Watt, 1% tolerance) R5, R6, R8, R9 100-ohm (4 pcs), brown-black-black-black-brown 270-ohm, red-purple-black-black-brown 470-ohm, yellow-purple-black-black-brown R3, 4, 19, 26, 37, 42, 45, 53-55, 62, 63 1K (12 pcs), brown-black-black-brown-brown R12, 13, 15, 16, 20, 22, 23, 25, 44, 56, 59 3.3K (11 pcs), orange-orange-black-brown-brown 3.9K, orange-white-black-brown-brown 4.3K, yellow-orange-black-brown-brown...

  • Page 7: Assembly

    SI5351A 10-pin MSOP (pre-soldered at factory) ATmega328P 28-pin microcontroller 74ACT00N 14-pin quad NAND gate FST3253 16-pin SOIC (pre-soldered at factory) IC5-10 LM4562 8-pin dual op-amp (6 pcs) IC11 7805, TO220 5V 1A voltage regulator Q1-5, 7 BS170 TO92 MOSFET (6 pcs) MPS751 TO92 transistor (MPS2907 in early kits) Inductors L1, 3...
  • Page 8 I recommend just install everything then power up. As per standard QRP Labs practice, the ATmega328P microcontroller has a 28-pin DIP socket in case you may wish to subsequently replace it for firmware upgrades etc. The Si5351A and FST3253 ICs are only available in surface mount packages so these are already soldered to the PCB for you, at the factory.
  • Page 9 QCX assembly Rev 1.08...
  • Page 10 QCX assembly Rev 1.08...
  • Page 11 The PCB track and circuit (schematic) diagrams are shown on the previous pages. Tracks shown in BLUE are on the bottom layer. Tracks shown in RED are on the top layer. There are only two layers (nothing is hidden in the middle). Not shown in this diagram are the extensive ground- planes, on both sides of the board.
  • Page 12 QCX assembly Rev 1.08...

  • Page 13: Inventory Parts

    Inventory parts Refer to parts list in section 2. The following photographs are to aid component identification. The resistors and capacitors are omitted. QCX assembly Rev 1.08...

  • Page 14: Install Ic2 Socket

    Install IC2 socket Install the 28-pin IC socket for IC2. Take care to match the dimple on the socket, with the dimple on the PCB silkscreen. It is critical to insert the microcontroller with the correct orientation. Lining up the dimple on the PCB silkscreen, socket and actual IC is the best way to avoid confusion and potential error.

  • Page 15: Install All 100Nf (0.1Uf) Capacitors

    It is normal to need to slightly squeeze the rows of pins inwards to fit in the holes on the PCB. IC manufacturers always supply leaded (through-hole) ICs with the pins a little too wide-spaced. As before, I find it useful to solder initially two pins at diagonal opposites of the chip, then check that the chip is nicely seated evenly on the board, before soldering the other pins.

  • Page 16: Install All 470Nf Capacitors

    Install all 470nF, “474” capacitors The 470nF capacitors are labelled “474”, and are capacitors C11, C43, C44, C45 and C46. QCX assembly Rev 1.08...

  • Page 17: Install All 1Nf Capacitors

    Install all 1nF, “102” capacitors The 1nF capacitors are labelled “102” and are capacitors C14, C16, C18, C23 and C33. Install all 10nF, “103” capacitors The 10nF capacitors are labelled “103” and are capacitors C4, C7, C10 and C42. QCX assembly Rev 1.08...

  • Page 18: Install 47Nf Capacitors

    Install 47nF, “473” capacitors The 47nF capacitors are labelled “473” and are capacitors C9 and C13. Install 39nF, “393” capacitor The 39nF capacitor is labelled “393” and is C17. It has 5mm pin spacing, unlike the others. QCX assembly Rev 1.08...

  • Page 19: Install 2.2Nf Capacitors

    Install 2.2nF, “222” capacitors 3.10 The 2.2nF capacitors are labelled “222” and are C19 and C20. Install 33nF, “333” and 3.3nF, “332” capacitors 3.11 These are labelled “333” and “332”, and in parallel make up 36nF. They are C15 and C53. QCX assembly Rev 1.08...

  • Page 20: Install Capacitors C25 And C26 From The Low Pass Filter Kit

    3.12 Install capacitors C25 and C26 from the Low Pass Filter kit The value of these capacitors depends on your chosen band. The capacitors are located inside the separate Low Pass Filter bag in your main kit bag. Refer to the following table to find the correct capacitor value for your band: Band Value...

  • Page 21: Install Capacitors C27 And C28 From The Low Pass Filter Kit

    3.13 Install capacitors C27 and C28 from the Low Pass Filter kit The value of these capacitors depends on your chosen bandThe capacitors are located inside the separate Low Pass Filter bag in your main kit bag. Refer to the following table to find the correct capacitor value for your band: Band Value...

  • Page 22: Install Capacitor C30

    3.14 Install capacitor C30 This capacitor is band dependent. The kit contains all required capacitor values for all bands. Install the one appropriate to your band. Refer to the following table to find the correct capacitor value for your band: Band Value Label...

  • Page 23: Install Capacitors C5 And C8

    3.15 Install capacitors C5 and C8 These capacitors are band dependent. They add parallel capacitance to trimmer capacitor C1 to bring it to the required value. The kit contains all required capacitor values. Install the capacitor(s) appropriate to your band. Refer to the following table to find the correct capacitor value(s) for your band.

  • Page 24: Install 1Uf Capacitor

    Install 1uF, “105” capacitor 3.16 The 1uF capacitor is labelled “105” and is C31. 3.17 Install 1N4148 diodes There are 4 small glass red-ish coloured diodes, D1, D2, D4 and D5. Note that D1, D2 and D5 are installed flat on the PCB (see photo, right).

  • Page 25: Install 1N5819 Diode

    3.18 Install 1N5819 diode This diode D3 is the larger diode with a black body, and a white stripe. It is installed horizontally. Again, it must be orientated correctly, with the white stripe on the diode matching the white stripe on the PCB.

  • Page 26: Install 20Mhz Crystal Xtal1

    3.19 Install 20MHz crystal XTAL1 The engraving on this crystal is “20.000”. QCX assembly Rev 1.08...

  • Page 27: Install 27Mhz Crystal Xtal2

    3.20 Install 27MHz crystal XTAL2 The engraving on this crystal is “27.000”. 3.21 Install all 10K resistors There are 15 10K resistors in the kit, these are R1, R2, R7, R10, R14, R34, R39, R40, R46, R49, R50, R51, R52, R57 and R58. The colour code is brown-black-black-red- brown.

  • Page 28: Install All 1K Resistors

    3.22 Install all 1K resistors There are 12 1K resistors in the kit, these are R3, R4, R19, R26, R37, R42, R45, R53, R54, R55, R62 and R63. The colour code is brown-black-black-brown-brown. QCX assembly Rev 1.08...

  • Page 29: Install All 3.3K Resistors

    3.23 Install all 3.3K resistors There are 11 3.3K resistors in the kit, these are R12, R13, R15, R16, R20, R22, R23, R25, R44, R56 and R59. The colour code is orange-orange-black-brown-brown. 3.24 Install all 100-ohm resistors There are four 100-ohm resistors in the kit, these are R5, R6, R8 and R9. The colour code is brown-black-black-black-brown.

  • Page 30: Install 120K Resistors

    3.25 Install 120K resistors There are three 120K resistors in the kit, these are R38, R43 and R60. The colour code is brown- red-black-orange-brown. 3.26 Install 33K resistors There are two 33K resistors in the kit, these are R28 and R29. The colour code is orange-orange- black-red-brown.

  • Page 31: Install 47K Resistors

    3.27 Install 47K resistors There are two 47K resistors in the kit, these are R30 and R31. The colour code is yellow-purple- black-red-brown. 3.28 Install 36K resistors There are two 36K resistors in the kit, these are R32 and R33. The colour code is orange-blue- black-red-brown.

  • Page 32: Install 270-Ohm Resistor R48

    3.29 Install 270-ohm resistor R48 This resistor has colour code red-purple-black-black-brown. 3.30 Install 470-ohm resistor R41 This resistor has colour code yellow-purple-black-black-brown. QCX assembly Rev 1.08...

  • Page 33: Install 3.9K Resistor R61

    3.31 Install 3.9K resistor R61 This resistor has colour code orange-white-black-brown-brown. 3.32 Install 4.3K resistor R18 This resistor has colour code yellow-orange-black-brown-brown. QCX assembly Rev 1.08...

  • Page 34: Install 5.1K Resistor R11

    3.33 Install 5.1K resistor R11 This resistor has colour code green-brown-black-brown-brown. 3.34 Install 7.5K resistor R21 This resistor has colour code purple-green-black-brown-brown. QCX assembly Rev 1.08...

  • Page 35: Install 750K Resistor R35

    3.35 Install 750K resistor R35 This resistor has colour code purple-green-black-orange-brown. 3.36 Install 100K trimmer potentiometer R47 This is the LCD contrast potentiometer. The label on R47 is “104”. Carefully apply firm pressure to install the component pins in the holes without bending them. QCX assembly Rev 1.08...

  • Page 36: Install 500-Ohm Multi-Turn Trimmer Potentiometer

    3.37 Install 500-ohm multi-turn trimmer potentiometer This resistor is the small blue box component with label “501”. It is R27. Make sure that the orientation is correct. The screw on the resistor must match the screw on the PCB silkscreen and layout diagram.

  • Page 37: Install Two 100Uh Inductors

    3.39 Install two 100uH inductors There are two 100uH inductors, L5 and L6. These look like short fat resistors. They are installed vertically on the PCB, in the same way as the resistors are installed. QCX assembly Rev 1.08...

  • Page 38: Install 10Uf Capacitors

    3.40 Install 10uF capacitors There are six 10uF capacitors in the kit: C21, C22, C24, C37, C38 and C51. These are polarised electrolytic capacitors and MUST be installed with the correct orientation! The capacitor NEGATIVE wire must be installed in the hole indicated on the PCB silkscreen and the layout diagram by the solid black bar;...

  • Page 39: Install 220Uf Capacitor C47 (May Be Supplied As 470Uf)

    3.41 Install 220uF capacitor C47 (may be supplied as 470uF) This capacitor is also a polarised electrolytic and must be orientated correctly (see former section). The height dimension of the supplied capacitor in the first batch (up to serial number 500) is enough that in some cases, if installed vertically on the PCB, it may touch some components on the bottom of the LCD module, once the LCD module is...

  • Page 40: Install 30Pf Trimmer Capacitor C1

    3.42 Install 30pF trimmer capacitor C1 Insert the component pins carefully and solder them QUICKLY to avoid overheating the capacitor which could melt the plastic insulating spacers. 3.43 Install MPS751 transistor Q6 (MPS2907 in first kit batch) Be careful to correctly identify this transistor by its markings, as the package style is similar to the other transistors.

  • Page 41: Install All Bs170 Transistors

    3.44 Install all BS170 transistors The remaining transistors in the kit are BS170 MOSFETs and there are six of them: Q1, Q2, Q3, Q4, Q5 and Q7. Follow the same installation procedure as the previous section. Note that Q7 sits under the volume (gain) knob. It is important to ensure that Q7 is pushed down as far as possible towards the board, so that the transistor lead length is only ~4mm, to avoid the top of the transistor blocking the knob.

  • Page 42: Install 4-Pin Gps Header

    3.46 Install 4-pin GPS header Install a 4-pin header from the Low Pass Filter kit bag, in the position shown. This is used to connect a GPS module if required. Insert the SHORT end of the pins into the PCB. 3.47 Install 3-pin DVM/RF detector header Take the other 4-pin header from the Low Pass Filter kit and carefully cut off 1 pin with a wire-...

  • Page 43: Install 1-Pin Test Points

    3.48 Install 1-pin test points Install 1-pin headers as test points, as shown. One of these is taken from the 4-pin header from the Low Pass Filter kit (see previous section); the other two are to be cut carefully from the 16-pin header supplied, leaving the 14-pin section intact.

  • Page 44: Install 7805 Voltage Regulator Ic11

    3.50 Install 7805 voltage regulator IC11 Install the 7805 voltage regulator, orientating it so that the metal tab is facing outwards from the PCB. Push the wires all the way down into the holes until the body of the regulator is about 5mm off the PCB surface.

  • Page 45: Wind And Install Toroid L4

    The wire is coated with an enamel insulating paint and it is CRITICAL to remove this enamel at the soldered joints otherwise there will be no electrical connection through the toroid! This is the number 1 cause of problems with QRP Labs kit construction: failure to remove the wire enamel. QCX assembly Rev 1.08...
  • Page 46 One method of removing the wire enamel is to scrape it off at the ends, either with sandpaper, or carefully scratching with a knife or wire cutters. However, my favourite method is just to burn off the enamel. For quite a number of years, the type of enamel used on copper wire can be burnt off using the temperature available from an ordinary soldering iron, immersing the wire...

  • Page 47: Wind And Install Toroid L2

    3.53 Wind and install toroid L2 L2 is a small toroid ring painted yellow or red on one side. It is part of the supplied Low Pass Filter kit bag. Again, keep the wire tight and evenly spaced around the toroid. Installation of the inductor is similar to the previous section.

  • Page 48: Wind And Install Toroids L1 And L3

    3.54 Wind and install toroids L1 and L3 L1 and L3 are small toroid rings painted yellow or red on one side. They are part of the supplied Low Pass Filter kit bag. Again, keep the wire tight and evenly spaced around the toroid. Installation of the inductor is similar to the previous section.

  • Page 49: Wind And Install Transformer T1

    3.55 Wind and install transformer T1 Now we come to the only really tricky piece of the assembly, which is the receiver input transformer T1. Follow these instructions carefully, it is tricky but quite feasible if you go step by step. In the end, you are going to end up with an installed transformer which hopefully looks something like the photo (right, shows 20m...
  • Page 50 QCX assembly Rev 1.08...
  • Page 51 The four windings on T1 must all be in the same “sense”. There are two ways to wind toroids. You might call them left-handed and right-handed; clockwise and counter-clockwise; whether the wire goes through the toroid from top to bottom, or from bottom to top. Whatever you call it, all the four windings have to be the same, to be sure to get the phasing to the quadrature sampling detector correct.
  • Page 52 In all cases, there is one long secondary winding, and three other short identical windings. To make things easier, we will wind all windings together in one go, this will guarantee that the “sense” of each winding will be the same. At the intended breaks between the windings, we will leave large loops of wire, that we can later cut one by one to make sure the wires go in the correct holes.
  • Page 53 toroid’s 39 windings. Count the windings to make sure you have 39. When you are sure everything is fine, cut the wire leaving about 3cm of wire free at the end. The remaining steps show the transformer installation on an otherwise empty PCB, to make the explanation clear.
  • Page 54 Finally, cut and un-twist the loop which you created first, which was between the 30 turns of the toroid winding. Push the wire which came over the toroid body, into hole 7. Now you have three turns of wire, which make up “secondary 2”, between holes 7 and The last wire came from under the toroid body when you cut the loop;...

  • Page 55: Install Rf Output Bnc Connector

    The final picture (18) shows the toroid installation completed. 3.56 Install RF output BNC connector Solder one pin first, to check that the alignment is correct; when happy, solder the remaining pins. The connector has RF and Ground connections, and two fat rods which are for mechanical stability only.

  • Page 56: Install 3.5Mm Stereo Connectors

    3.57 Install 3.5mm stereo connectors These connectors are used for the audio output (earphones) and for optional connection of a paddle. The sockets are a VERY tight fit, but they DO fit, with care, eventually. When you are happy that the socket is neatly aligned and seated on the PCB, solder the remaining pins. 3.58 Install buttons S2 and S3 (left and right buttons) These buttons (or other push-to-make buttons) may alternatively be wired off-board, for example...

  • Page 57: Install Rotary Encoder

    3.59 Install rotary encoder This switch has seven solder pads: five are for electrical connections and the two large tabs are for mechanical stability. You may also choose to mount the switch off-board, for example on a front panel. Refer to the later section describing the wiring. Remember that it will be difficult to remove the switch later, so you may wish to make the external mounting decision now.

  • Page 58: Install Gain Control Potentiometer R36

    3.61 Install gain control potentiometer R36 Carefully bend the pins of the potentiometer upwards 90-degrees as shown in the photograph. Remove the nut from the potentiometer, fit the shaft through the hole in the PCB, and carefully install the bolt and tighten with pliers. There is an anti-rotation tab on the metal case, which fits in the smaller hole to the right of the main shaft hole.

  • Page 59: Install Four 12Mm Hex Spacers At The Lcd Corners

    3.62 Install four 12mm hex spacers at the LCD corners Install the four 12mm spacers on the top side of the PCB, threading four M3 nylon screws through from the underside of the PCB. These four spacers fix the LCD module to the PCB assembly. 3.63 Install four 12mm hex spacers at the PCB corners These spacers are installed on the bottom side of the PCB, with the four M3 screws threaded...

  • Page 60: Install Knobs

    3.64 Install knobs Two black knobs are supplied, one for the rotary encoder and one for the gain control. When fitting the gain control knob, you should ensure that when the potentiometer is turned all the way anti- clockwise, the white pointer on the knob points to the bottom left corner of the PCB. This is the conventional alignment for volume control knobs.

  • Page 61: Connections For Off-Board Mounting Of Controls

    3.68 Connections for off-board mounting of controls The following wiring diagram shows the connections between the PCB pads and controls (buttons, rotary encoder, gain potentiometer) that should be made if you intend to wire the controls off- board. For example, you may wish to install the radio in an enclosure and mount the controls on a front-panel.

  • Page 62: Connections For Basic Operation

    3.69 Connections for basic operation The following diagram illustrates the basic connections for transceiver operation. A power supply is required, which needs to be able to supply up to 0.5A on transmit. The supply voltage may be from 7 to 16V, and the RF power output will depend on the supply voltage (higher output power is produced at higher supply voltages).

  • Page 63: Adjustment And Alignment

    3.70 Adjustment and alignment The first thing that you will notice when you apply power to the radio, is that there is probably nothing at all shown on the display. This is because you need to adjust the contrast trimmer potentiometer R47 at the top right of the PCB! Adjust it with a screwdriver until the display text looks right to you.
  • Page 64 In summary: the alignment tools built into the radio consist of a signal generator which injects a signal into the RF front end, and digital signal processing which adds a 250-Hz digital filter to the existing 200Hz analogue filter, and calculates the amplitude of the signal detected in that bandwidth.
  • Page 65 Adjustment of the C1 trimmer capacitor should change the size of the amplitude bar. You need to adjust the C1 trimmer for MAXIMUM amplitude. When this is done, the peak of the band pass filter will be centred on the CW section of the band. It is very important to understand the number at the top right of the LCD, here shown as 09.
  • Page 66 20MHz system clock oscillator of the microcontroller. These adjustments can be made manually, or by connection of a GPS module such as the QRP Labs QLG1 GPS receiver kit. However, since this calibration is a lot less urgent than the Band Pass Filter peaking and...

  • Page 67: Operating Instructions

    unwanted sideband cancellation, they are left until the description of these menu items in the operating manual. Following the adjustment of these alignment trimmers, the radio is ready to use. A lot of settings are available in the configuration menu, and you should read the operation manual to understand and make use of all the features! 4.
  • Page 68 Owners of the QRP Labs Ultimate-series weak signal mode transmitter kits will be familiar with the operation of WSPR. A GPS module such as the QRP Labs QLG1 GPS receiver kit can optionally be connected to this CW transceiver kit to provide frequency and time discipline, as well as setting the Maidenhead locator (from latitude and longitude) that is encoded in the WSPR message.

  • Page 69: Display Elements

    Display elements The kit uses a 2 row, 16 character LCD module with a blue backlight. The main display layout during ordinary operation (which will be called “main operating mode”) is shown in the above photograph. The display during beacon or message transmission modes, menu editing, alignment etc.

  • Page 70: Operator Controls

    Operator controls This diagram shows the operating controls of the radio. All of the controls except the Gain potentiometer have multiple functions, depending on the operating mode, menu editing, etc. The tuning rotary encoder in the centre has a button on its shaft that is activated by pressing it, and this button also has multiple functions.

  • Page 71: Keyer Speed

    Keyer speed The default keyer speed (in words per minute) at start-up is a configuration item in the Keyer menu (see later). During operation of the radio, the keyer speed can be easily adjusted. Click the left button once, and the speed will be displayed on the screen: A14,006,50 Speed 12 Now you can adjust the speed using the rotary encoder.

  • Page 72: Vfo Mode

    VFO mode A single press on the right button changes the active VFO mode. There are two independent VFOs named A and B. There are three VFO modes for using these VFOs: • VFO A is active as transmit and receive VFO; if non-zero, RIT is applied during receive •...

  • Page 73: Automated Message Transmission Mode

    4.10 Automated message transmission mode My favourite use of the automated message transmission mode is to send a CQ call repeatedly. If a station answers, you can start transmitting and it cancels the automatic CQ mode. There are 12 message memories. The first four memories are 100 characters long; the remaining eight memories are 50 characters long.

  • Page 74: Saving Current Operating Parameters (Vfo Frequency Etc)

    The menus are organised into 9 groups as follows: • 1. Preset • 2. Messages • 3. VFO • 4. Keyer • 5. Decoder • 6. Beacon • 7. Other • 8. Alignment • 9. Test equipment • Save settings! To enter the menu system, give a single long press to the left (select) button.

  • Page 75: Types Of Configuration Menu Item

    4.13 Types of configuration menu item There are five types of menu configuration item, and editing these is a little different depending on the type. 1) LIST: a fixed list of values applicable to that menu item, for example Keyer mode 2) BOOLEAN: an ON/OFF parameter, such as used to control whether the battery icon shows 3) NUMBER: a numeric parameter such as a stored frequency preset 4) TEXT: a text configuration item such as a stored message...

  • Page 76: Editing A Number Parameter

    4.17 Editing a NUMBER parameter When editing a number parameter, the cursor underline appears under the currently edited digit. The cursor starts at the far left (most significant digit). The rotary encoder tunes the digit. The operation is very similar to tuning a VFO in ordinary operation. This example shows editing the default (power-up) VFO A frequency: To alter the “tuning rate”, you can either a) Press the left (select) button to move the cursor to the next digit to the right OR...
  • Page 77 It is also possible to edit a text parameter entirely with the buttons and rotary encoder, though this is usually a slower way to edit text parameters. Owners of the QRP Labs Ultimate3S (or earlier) QRSS/WSPR transmitter kits will already be familiar with this style of editing text.

  • Page 78: Frequency Presets Menu

    4.19 Frequency presets menu There are 16 frequency presets, labelled 1 to 16. This example shows Preset 5: 1.5 Preset 5 14,020,000 All of the Preset menu items are NUMBER types. Refer to the “Editing a NUMBER parameter” section above for instructions on how to edit a NUMBER parameter. It is also convenient to load the current VFO into the preset memories as described in the section above titled “Frequency Presets”.

  • Page 79: Vfo Menu

    2.13 Interval The Interval is a NUMBER parameter that specifies the interval in seconds, between repeated transmission of a stored message (if repeats are configured: see next parameter). 2.14 Repeats Ad infinitum The Repeats parameter specifies how many times the message transmission will be repeated, in the repeat transmission mode.
  • Page 80 3.3 VFO B 14,032,500 This parameter specifies the VFO B frequency at power-up. The current VFO B frequency during ordinary operation is not stored in this parameter unless you “Save settings” as described previously. 3.4 Tune rate 100 Hz This LIST parameter specifies the Tune rate power-up. Available values are: 10MHz, 1MHz, 100kHz, 10kHz, 1kHz, 500Hz, 100Hz, 10Hz or 1Hz.

  • Page 81: Keyer Menu

    3.8 CW offset This parameter specifies the CW offset in Hz. It is the difference between the VFO frequency during transmit and receive. It is automatically applied during receive in order to resolve a perfectly netted transmission on the same frequency as yours, at 700Hz audio output. If you wish to change the CW offset frequency you may do so using this parameter.
  • Page 82 If you wish to use a traditional up/down Morse key, or the onboard microswitch, these are called “straight” keys and you should select the “Straight” mode. If you wish to use a modern paddle plugged into the 3.5mm socket on the right side of the transceiver PCB, then select the desired operating mode e.g.
  • Page 83 If the weight is increased from the default 50.0%, then the key-down “dit” is made longer. A “dah” is lengthened by the SAME amount. The corresponding inter-symbol (or character, or word) gap is shortened by the same amount. The additional time spent on the key-down is therefore taken from the key-up period.
  • Page 84 Semi: After key-up, there is a delay before the Transmit/Receive switch is set back to “Receive” mode. The receiver is therefore kept muted during your whole CW transmission, not listening to the band in between your transmitted symbols. Many operators prefer to avoid the distraction of hearing the band between their dits and dahs.

  • Page 85: Decoder Menu

    4.23 Decoder menu The Decoder menu contains a number of configuration parameters relating to the CW decoder, which are described below. Some of these parameters control some aspects of the decoder behaviour. Some constructors may find it interesting to experiment with these settings and see if you can improve the performance of the CW decoder in your specific circumstances.
  • Page 86 5.3 Ampl. Avg. The decoder maintains an amplitude threshold, which it uses to decide whether a tone is detected or not. The level of this threshold must be varied automatically in order to cope with stations having a wide range of different signal strengths. Other perils may include QSB (signal fading) of the station you are listening to.

  • Page 87: Beacon Menu

    4.24 Beacon menu The beacon function is an added bonus feature of this QRP Labs CW transceiver kit! We already have extensive experience for several years, developing the Ultimate-series QRSS/WSPR transmitter kits (current incarnation, the Utimate3S). These have a huge array of functionality and modes including CW, QRSS, DFCW, FSKCW, Hellscreiber (full speed and slow FSK), WSPR, JT9, JT65, ISCAT, Opera and PI4.
  • Page 88 locator will be calculated from the received latitude and longitude, and the time decoded nicely from the GPS serial data stream. The microcontroller in this kit takes care of the WSPR message encoding algorithm, without any assistance from a PC host computer. It also calculates the tone spacing and symbol duration. In between message transmissions, the display will show instead just a clock (see below), while we wait patiently for the next WSPR transmission to begin, according to the settings of the configuration parameters Frame and Start.
  • Page 89 On a PC spectrum display such as the Argo software http://www.weaksignals.com/ WSPR messages look something like the screenshot below when received locally (or usually worse, because you probably are over-driving your receiver when receiving your own signal!): WSPR decoding takes place in the WSPR program by K1JT (see http://physics.princeton.edu/pulsar/K1JT/wspr.html ).
  • Page 90 The following sections describe the configuration parameters in the Beacon menu. 6.1 Beacon This is the master switch controlling whether beacon mode is enabled or not. If beacon mode is enabled, then the radio starts operating in beacon mode on power-up. While beacon mode is operational, it can be cancelled immediately at any time by pressing the right (exit) button.
  • Page 91 Therefore, ensure that for WPSR transmissions, you choose a frequency in one of the WSPR sub- bands according to the following table: 3.594000 – 3.594200 80m: 5.288600 – 5.288800 60m: 7.040000 – 7.040200 40m: 10.140100 – 10.140300 30m: 14.097000 – 14.097200 20m: 18.106000 –...
  • Page 92 The callsign can only be 4 to 6 characters long. The callsign must consist of the following: One character which can be A-Z or 0-9 or a SPACE One character which can be A-Z or 0-9 One character which must be a number 0-9 Three characters which can be A-Z or a SPACE For callsigns such as mine, consisting of 5 characters, I must enter a space character as the first character in order to satisfy these callsign rules.
  • Page 93 WSPR powers are constrained to certain values 0, 3, 7, 10, 13, 17, 20, 23, 27, 30, 33, 37, 40, 43, 47, 50, 53, 57 and 60dBm. If you specify a value not in this list, then an error message will be generated on exiting the configuration menu system.

  • Page 94: Other Menu

    4.25 Other menu This menu contains miscellaneous other settings which do not fit well in other configuration menu categories. 7.1 Dbl. click This is a NUMBER parameter which controls the decisions on what type of press has been made to a button. By default, it is set to 300 milliseconds (as shown here) but you may alter this if you wish.
  • Page 95 7.4 Batt. step 1,000 This is the step, specified in millivolts, for each bar of the battery icon. In this example, Batt. full is defined as 13.8V and the step is 1V. The battery icon has 7 possible states, ranging from empty to full and 5 intermediate states in between. The meaning of the displayed icon will be, in this example: •...

  • Page 96: Alignment Menu

    7.7 S-meter step This NUMBER parameter effectively defines the sensitivity of the S-meter. The S meter has 12 bars maximum. Each bar of the S-meter equates to the specified “S-meter step” number on the amplitude measurement scale. So, in this case the scale of the 12 bars of the S-meter will mean 0 to 1200 in amplitude measurement terms.
  • Page 97 8.1 Align frq 14,020,000 The Align frq. parameter specifies the frequency which the alignment tools operate. You should ensure that the frequency specified is in the centre of the CW section of the band of operation of your radio. 8.2 I-Q bal frq The audio frequency at which the I-Q balance adjustment is performed.
  • Page 98 If a GPS unit is available, then this makes everything very simple – then you can use the GPS calibration tools to calibrate this value (see below). 8.6 System frq 20,000,000 The system oscillator frequency. In this radio, the microcontroller clock is a 20MHz crystal. If you are able to measure the actual 20MHz frequency (without disturbing it), you can enter the frequency here.
  • Page 99 8.11 Cal ref osc Press Select! If you have connected a GPS receiver module such as the QRP Labs QLG1 GPS receiver http://qrp-labs.com/qlg1 with a one pulse per second (1pps) output signal, then when you press the left (select) button the microcontroller uses the 1pps as a frequency counter gate.

  • Page 100: Test Equipment

    8.12 Cal sys osc Press Select! If you have connected a GPS receiver module such as the QRP Labs QLG1 GPS receiver http://qrp-labs.com/qlg1 with a one pulse per second (1pps) output signal, then when you press the left (select) button the microcontroller uses the 1pps as a frequency counter gate. It counts the 20MHz system clock internally for 4 seconds to obtain a frequency count.
  • Page 101 9.1 Voltage 11.67V This the Digital Voltmeter (DVM) function. The measurable voltage range is 0-20V DC. When the on-screen battery voltage display is used, you must connect the DVM input pin to the +V output pin (refer to previous diagram showing these connections). In this example, a 12V power supply is being used to power the radio.
  • Page 102 9.3 Audio Ch.1 01,652 This item just displays the raw amplitude number calculated by the Goertzel algorithm for the audio channel 1, which is connected to the output of the audio amplifier. The value shown here will depend on the input signal level but also on the gain control. You can easily verify that as you turn up the gain control knob, the displayed value increases.
  • Page 103 9.6 Signal gen. 25,124,093 The signal generator function is switched off until you press the left button to select it. Then the cursor appears under the 10MHz digit. You can then adjust this number just like any other configuration parameter. Use the rotary encoder to increase or decrease the frequency. Press-and hold, then turn the rotary encoder, to change the tune rate (move the cursor left or right).

  • Page 104: Circuit Design

    5. Circuit design of the QCX Block diagram and summary This CW transceiver is a high performance, yet simple and low cost, analogue design. The transmitter uses a high efficiency Class-E amplifier which results in low current draw on transmit, and inexpensive transistors with no heatsinks.
  • Page 105 QCX assembly Rev 1.08...

  • Page 106: Circuit Diagram

    The synthesiser section of the circuit diagram is shown here (right). The Si5351A datasheet dictates the use of a 25 or 27MHz crystal. QRP Labs has always used the 27MHz crystal in our designs because it allowed us to obtain precise 1.46Hz tone spacing for WSPR...

  • Page 107: Transmit/Receive Switch

    The Si5351A has a phase offset feature, which is not really very clearly described in the SiLabs documentation. However, QRP Labs has perfected the technique to put two of the Si5351A outputs into precise 90-degree quadrature, which is maintained without tuning glitches as the frequency is altered.

  • Page 108: Band Pass, Phase Splitter, Qsd And Pre-Amps

    The switch wouldn’t provide enough attenuation to mute an operating receiver; but during receive, our receiver isn’t operating; all the switch has to do is protect the Quadrature Sampling Detector from seeing 45V peak-peak which would destroy it. Band Pass, Phase Splitter, QSD and pre-amps Since the band-pass filter, Phase splitter, Quadrature Sampling Detector and pre-amp circuits are so tied up together, I am going to consider them all together in this section.

  • Page 109: 90-Degree Audio Phase Shift

    Despite the high IP3 and dynamic range, it is still prudent to provide some input band pass filtering to protect the mixer from strong out of band signals. In this CW transceiver design, the T1 transformer provides a simple solution to all of these problems with a very low parts count. The primary couples the incoming RF into the two secondary windings which feed the double- balanced detector.

  • Page 110: Cw Filter

    In the real world, nothing is perfect – there are component tolerances to think about. The unwanted sideband suppression is maximised when the amplitude of the two paths is equal, and the 90-degree phase shift is accurate. To improve the accuracy of the 90-degree phase shift, R17 and R24 allow adjustment of the phase shift at higher and lower audio frequencies respectively.
  • Page 111 R36 is a logarithmic potentiometer used as the gain control. With the wiper fully clockwise the receiver is at full volume. As the potentiometer is turned anticlockwise it forms a potential divider which attenuates the audio signal from the CW filter output. There is also a TX mute switch formed by Q7, another BS170 MOSFET.

  • Page 112: Transmit Signal Routing And Pa Driver

    Transmit signal routing and PA driver The 74ACT00 is a quad NAND logic gate. The input threshold voltage for a binary “1” is 2.4V which means that the gate is easily switched on by the ~3.3V peak-peak squarewave output from the Si5351A.
  • Page 113 Some excellent background reading are two papers by Paul Harden NA5N: http://www.aoc.nrao.edu/~pharden/hobby/_ClassDEF1.pdf http://www.aoc.nrao.edu/~pharden/hobby/_ClassDEF2.pdf Paul NA5N describes two defining features of Class-E: 1) Use of a square-wave drive to reduce switching losses: the transistors are either on, or off… no lossy region in between 2) Reducing the effects of the transistor capacitances.

  • Page 114: Low Pass Filter

    Low Pass Filter The transmitter output is rich in harmonics and must be followed by a good Low Pass Filter, to attenuate the harmonics and satisfy regulatory compliance. The standard, well-proven QRP Labs Low Pass Filter kit http://qrp-labs.com/lpfkit is used here. To save space and cost, the components are installed directly on the PCB, not on a plug-in board.
  • Page 115 The simple key-shaping circuit used here uses only a few components but produces good results. This circuit was derived by one published by Don Huff W6JL, see https://www.qrz.com/db/W6JL/ though as he says, “this integrator-type keying circuit is found in many published homebrew designs over the past 40 years or so, so it is nothing new”.

  • Page 116: Microcontroller

    The ATmega328P was chosen because it has enough processing power and I/O to handle all the tasks required here. It is also common and inexpensive, and lots of QRP Labs products already used it, bringing economies of scale in both the kit preparation and the coding. The processor is operated at its maximum rated 20MHz system clock speed.
  • Page 117 To combat the radiation issue, the ATmega328P microcontroller is sited at the back of the board, right under the LCD module. The tracks between the LCD module and the microcontroller are therefore kept as short as possible, to minimise radiated noise. To keep noise out of the supply, the 5V supply to the microcontroller and LCD module is filtered by 100uH inductor L6 and 220uF capacitor C47 (may be supplied as 470uF, even better!).
  • Page 118 All mechanical switches exhibit switch bounce, where the switch contacts generate multiple transitions for a short time when the switch is activated. It is common to see in many projects, resistor-capacitor networks to debounce switches (including the rotary switch). Simple debounce circuits involving a resistor and a capacitor inevitably involve a compromise when choosing the R- C time constant.

  • Page 119: Optional Gps Interface

    In all three cases, the voltage when a button is pressed, is higher than the 3V logic “1” threshold of the microcontroller. I am able to use a pin-change interrupt to detect that a button has been pressed, then read the ADC channel 3 and compare the measured voltage to the table, to determine which button was pressed.

  • Page 120: In Circuit Programming (Isp) Interface

    3.5mm socket for the keyer. The pinout of the 4-pin header exactly matches the one on the QRP Labs Ultimate3S QRSS/WSPR transmitter kit, and the QRP Labs QLG1 GPS receiver kit. This makes connecting the radio to the QLG1 GPS kit very easy, if you wish. However other GPS modules could also be used.
  • Page 121 DVM and RF Power meter The DVM and RF Power meter is implemented using the 10-bit ADC channel 2 input to the microcontroller. When measuring voltage, connect the voltage to be measured to pin 3 of the 3-pin DVM/RF Power connector.
  • Page 122 Frequency Counter The frequency counter test pin input is connected directly to the microcontroller’s 16-bit Timer1 input pin. There is a 1K series resistor (R55) to connect it also to the Si5351A’s Clk2 output. This is used during the optional GPS-disciplined 27MHz reference crystal frequency measurement.

  • Page 123: Voltage Regulator

    In the photograph, the white wire shown looping around the rotary encoder connects the FREQ pin (just under the “M” character of the LCD, in the photograph) to the Clk0 output pin (just under the “z” character of the LCD). This is a convenient way to get the frequency counter to verify the correct operation of the signal generator (and hence the Si5351A synthesiser).

  • Page 124: A Row Of Blocks Appears On The Top Row

    A row of blocks appears on the top row If you see a row of blocks along the top of the LCD module, and the bottom row is empty, this means that the microcontroller has not communicated with the LCD module. Check that your IC2 microcontroller is correctly installed in its 28-pin socket, with the correct orientation (dimple on the chip matches the dimple on the socket and the PCB silkscreen).
  • Page 125 Location Voltage Comment + supply terminal 11.98 As I already mentioned: a 12V supply Clk0 test pin ~1.70 The Clk0 pin in normal operation has a 3.3V peak-peak squarewave with 50% duty cycle. The DVM is measuring the average of that. Measuring here makes a lot of nasty noise in the audio.

  • Page 126: Rf Power Output Check

    IC8 pin 8 11.67 IC9 pin 1 4.84 IC9a output IC9 pin 2 4.84 IC9 pin 3 0.65 IC9 pin 4 0.00 IC9 pin 5 0.67 IC9 pin 6 2.44 IC9 pin 7 2.44 IC9b output IC9 pin 8 11.67 IC10 pin 1 5.83 IC10a output...

  • Page 127: Audible Continuous Clicking Noise During Receive

    If you do NOT see any power output on key-down, then you probably have a fault in the Power Amplifier. A common mistake, as I mentioned previously during the assembly steps, is failure to remove or burn off the enamel insulation on the enamelled copper wire wound onto the toroids. Check the RF power wire touched to the BS170 drains first (see diagram).

  • Page 128: Equipment

    • XONAR U5 24-bit external USB sound card • Argo and Spectran audio analysis software from http://weaksignals.com • QRP Labs Ultimate3S for test signal generation http://qrp-labs.com/ultimate3/u3s • Simple 14.000MHz battery-powered crystal oscillator signal generator • Two generic yellow DVMs •...

  • Page 129: Transmitter Power Output

    Transmitter power output The transmitter RF power output varies depending on the power supply voltage. It is also dependent on band. Your results may vary depending on your Low Pass Filter inductor construction! If the cut-off frequency becomes too low, then you can start to get attenuation at the operating frequency.

  • Page 130: Class-E Power Amplifier Drain Waveform

    Class-E Power Amplifier drain waveform This oscilloscope chart shows the waveform at the BS170 drains (top, RED colour trace) and the input drive waveform, a 5V peak-peak squarewave (bottom, BLUE trace). The 40m band is shown. Upon ignoring the “ringing” artefacts due to poor ‘scope probes etc., the waveforms are correct for Class-E operation.

  • Page 131: Low Pass Transmitter Harmonic Output Filter Characteristics

    Low Pass transmitter harmonic output filter characteristics The Low Pass Filter response was not measured. The Low Pass Filter is the same as the QRP Labs Low Pass Filter kit module http://qrp-labs.com/lpfkit . Measurements of the Ultimate3S kit http://qrp-labs.com/ultimate3/u3s using these filters is on this page http://www.qrp- labs.com/ultimate3/u3info/u3spec.html Band Pass receiver input filter characteristics...
  • Page 132 60m band 3dB bandwidth: 367kHz Insertion loss: 1.45dB at 5.357MHz centre Tuning range: 4.63MHz to 5.91MHz 40m band 3dB bandwidth: 514kHz Insertion loss: 1.97dB at 7.020MHz centre Tuning range: 6.04MHz to 8.36MHz QCX assembly Rev 1.08...
  • Page 133 30m band 3dB bandwidth: 645kHz Insertion loss: 2.67dB at 10.120MHz centre Tuning range: 7.93MHz to 12.47MHz 20m band 3dB bandwidth: 1,083kHz Insertion loss: 1.30dB at 14.020MHz centre Tuning range: 9.69MHz to 22.54MHz QCX assembly Rev 1.08...

  • Page 134: Quadrature Sampling Detector Bandwidth

    17m band 3dB bandwidth: 1,352kHz Insertion loss: 2.77dB at 18.120MHz centre Tuning range: 12.64MHz to 35.0MHz Quadrature Sampling Detector bandwidth The following chart shows the attenuation naturally provided by the Quadrature Sampling Detector from -20kHz to +20kHz from the Local Oscillator frequency. The narrow characteristic of this circuit is an advantage because it effectively adds an additional narrow RF bandpass filter to the receiver, preventing strong nearby signals from reaching the audio amplifier stages.

  • Page 135: Cw Filter Response

    The following chart shows the Quadrature Sampling Detector roll-off over the narrower range 0 to 5kHz. You can see that at the CW operating frequency 700Hz, the attenuation is insignificant; the roll-off of the QSD does not significantly improve the selectivity of the CW filter, but it does improve the intermodulation characteristics of the receiver.

  • Page 136: Unwanted Sideband Rejection

    7.10 Unwanted sideband rejection The following chart shows the measured level of the Upper Sideband signal (USB) and the unwanted Lower Sideband signal (LSB) when tuning the receiver through a strong test signal. The curves depend very heavily on the I-Q balance and audio phase shift adjustments, and these curves are from one measured prototype.

  • Page 137: Operation Reference "Cheat Sheet

    8. Operation reference “cheat sheet” Main controls functions: Left single press: Keyer speed Encoder turn: tuning, menu Right single press: change VFO adjust, then left again to select, or selection, editing, etc mode: A, B, Split right to cancel. Encoder press: change tune rate Right Double press: Select Left double press: RIT adjust, then 1kHz->500Hz->100Hz->10Hz...

  • Page 138: Resources

    9. Resources • For updates relating to this kit please visit the QRP Labs CW transceiver kit page http://qrp-labs.com/qcx • For any questions regarding the assembly and operation of this kit please join the QRP Labs group, see http://qrp-labs.com/group for details Document Revision History 1.00 02-Aug-2017...

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