QRP Labs QCX 5W CW Assembly Instructions Manual Download Page 1

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QCX assembly Rev 1.08

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

)

Summary of Contents for QCX 5W CW

Page 1: ...mbly 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 pict...

Page 2: ...z crystal XTAL2 27 3 21 Install all 10K resistors 27 3 22 Install all 1K resistors 28 3 23 Install all 3 3K resistors 29 3 24 Install all 100 ohm resistors 29 3 25 Install 120K resistors 30 3 26 Insta...

Page 3: ...nstall 16 pin female connector on LCD module 60 3 66 Install microcontroller 60 3 67 Install LCD and the remaining 4 screws to bolt LCD module 60 3 68 Connections for off board mounting of controls 61...

Page 4: ...ment 120 5 17 5V voltage regulator 123 6 Fault finding 123 6 1 Blank LCD or blocked LCD 123 6 2 No backlight at all 123 6 3 A row of blocks appears on the top row 124 6 4 DC voltage readings 124 6 5 R...

Page 5: ...Connectors Power 3 5mm keyer jack 3 5mm stereo earphone jack BNC RF output Onboard microswitch can be used as a simple straight Morse key Built in test signal generator and alignment tools to complet...

Page 6: ...rown R32 33 36K 2 pcs orange blue black red brown R38 43 60 120K 3 pcs brown red black orange brown R35 750K purple green black orange brown R27 500 ohm multi turn trimmer potentiometer R17 24 50K mul...

Page 7: ...5mm stereo 3 5mm stereo connector 2pcs BNC PCB mounting BNC connector S1 Microswitch S2 3 6 x 6mm push to make button 2 pcs SW1 Rotary encoder with shaft push button 16 x 2 LCD HD44780 LCD 1602 with...

Page 8: ...that the folded over wire end of the resistor doesn t touch any other wire or metal part Please refer to the layout diagram and PCB tracks diagrams below and follow the steps carefully Assembly steps...

Page 9: ...QCX assembly Rev 1 08 9...

Page 10: ...QCX assembly Rev 1 08 10...

Page 11: ...he result wouldn t be such a cute and neat little radio and the price wouldn t be so friendly either So check carefully before soldering each component Check the location and check again with referenc...

Page 12: ...QCX assembly Rev 1 08 12...

Page 13: ...QCX assembly Rev 1 08 13 3 1 Inventory parts Refer to parts list in section 2 The following photographs are to aid component identification The resistors and capacitors are omitted...

Page 14: ...al Inline Package integrated circuits IC3 and IC5 10 We install these now because they have more pins than all the passive components resistors capacitors etc and it is easiest to reach and install th...

Page 15: ...C49 C50 and C52 Place each in the correct position on the board and slightly bend the legs outwards at about 30 degrees angle so that they stay in place Then solder the wires and trim the excess wire...

Page 16: ...QCX assembly Rev 1 08 16 3 5 Install all 470nF 474 capacitors The 470nF capacitors are labelled 474 and are capacitors C11 C43 C44 C45 and C46...

Page 17: ...3 6 Install all 1nF 102 capacitors The 1nF capacitors are labelled 102 and are capacitors C14 C16 C18 C23 and C33 3 7 Install all 10nF 103 capacitors The 10nF capacitors are labelled 103 and are capa...

Page 18: ...18 3 8 Install 47nF 473 capacitors The 47nF capacitors are labelled 473 and are capacitors C9 and C13 3 9 Install 39nF 393 capacitor The 39nF capacitor is labelled 393 and is C17 It has 5mm pin spaci...

Page 19: ...19 3 10 Install 2 2nF 222 capacitors The 2 2nF capacitors are labelled 222 and are C19 and C20 3 11 Install 33nF 333 and 3 3nF 332 capacitors These are labelled 333 and 332 and in parallel make up 36n...

Page 20: ...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...

Page 21: ...e 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 you...

Page 22: ...ires both the 30pF and 56pF capacitors to be soldered in parallel but there is only one component position on the PCB For 60m you will need to install one of the capacitors e g 56pF in the component h...

Page 23: ...tains 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 Where none is indicated in the tab...

Page 24: ...t way around these are a polarised component and must only be installed in the PCB with the correct orientation In the case of D1 D2 and D5 the PCB silkscreen printing shows a white stripe at the end...

Page 25: ...board the wrong way around you do not destroy it A Schottky diode is used because the forward conducting voltage drop is less than an ordinary diode However on transmit the voltage drop across this di...

Page 26: ...QCX assembly Rev 1 08 26 3 19 Install 20MHz crystal XTAL1 The engraving on this crystal is 20 000...

Page 27: ...R34 R39 R40 R46 R49 R50 R51 R52 R57 and R58 The colour code is brown black black red brown All of the resistors in the kit are installed vertically see photo right Resistors are not polarised componen...

Page 28: ...QCX assembly Rev 1 08 28 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...

Page 29: ...stors 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...

Page 30: ...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...

Page 31: ...ors 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 R3...

Page 32: ...embly Rev 1 08 32 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...

Page 33: ...ssembly Rev 1 08 33 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 b...

Page 34: ...assembly Rev 1 08 34 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 br...

Page 35: ...s 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 i...

Page 36: ...The screw on the resistor must match the screw on the PCB silkscreen and layout diagram 3 38 Install 50K multi turn trimmer potentiometers There are two 50K multi turn trimmer potentiometers R17 and R...

Page 37: ...y Rev 1 08 37 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...

Page 38: ...e capacitor NEGATIVE wire must be installed in the hole indicated on the PCB silkscreen and the layout diagram by the solid black bar the POSITIVE wire must be installed in the hole indicated on the P...

Page 39: ...module once the LCD module is installed Therefore the recommended way to install this capacitor is orientated horizontally Insert the wires into the holes carefully putting the correctly polarised wir...

Page 40: ...51 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 Carefully bend and insert the wire...

Page 41: ...ortant 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 3 45 Install 2x3 pin in...

Page 42: ...pin header from the Low Pass Filter kit and carefully cut off 1 pin with a wire cutter without damaging its plastic base The headers are designed to break apart easily like this Keep the 1 pin section...

Page 43: ...w 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 3 49 Install power connector Install the 2 way power conn...

Page 44: ...le has an 8 bit data bus but can also be operated in 4 bit data mode which is what is done in this kit The 4 bit mode has the advantage that less pins of the microcontroller are used This is very impo...

Page 45: ...worry about these variations which are not critical in this case Band Value Turns 80m 2 3uH 24 60m 2 3uH 24 40m 1 0uH 16 30m 0 78uH 14 20m 0 40uH 10 17m 0 32uH 9 Try to keep the wire quite tight but n...

Page 46: ...out while you are trying to solder the wires Cut off the excess wire using wirecutters leaving only about 2mm protruding through the PCB on the lower side Now apply solder quite generously from the so...

Page 47: ...section Remember to remove the wire enamel and check The number of turns is band dependent refer to the following table Inductance values are approximate and will depend on variations in the core and...

Page 48: ...previous section Remember to remove the wire enamel and check The number of turns is band dependent refer to the following table Inductance values are approximate and will depend on variations in the...

Page 49: ...ersion This transformer has FOUR windings Three identical short windings and one long winding There are therefore eight wire ends which must all be soldered into the correct holes on the PCB and with...

Page 50: ...QCX assembly Rev 1 08 50...

Page 51: ...structions in this section refer to the 20m version 30 3 3 3 turns But MAKE SURE you wind the correct number of turns for your band Band Primary Secondary 1 Secondary 2 Secondary 3 80m 5 5 5 68 60m 5...

Page 52: ...e after each pass through the centre hole to try to keep the windings tight and even The wire turns should sit neatly side by side on the toroid without overlapping 3 Grip the toroid between thumb and...

Page 53: ...roid then passes through hole 6 So insert this wire into hole 5 Once again to be clear you should now have a winding of three turns which is labelled secondary 1 above with one end inserted into hole...

Page 54: ...e pair that you installed last un twisted 17 Now you can solder the eight connections under the PCB I recommend doing one pair of wires at a time this way the other wires will hold the toroid in place...

Page 55: ...oid 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 connect...

Page 56: ...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 righ...

Page 57: ...itch 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...

Page 58: ...which fits in the smaller hole to the right of the main shaft hole The tab hole is near to C52 on the right of the potentiometer When tightening the nut ensure that the pins remain aligned with the c...

Page 59: ...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 sc...

Page 60: ...is to temporarily assemble the modules and bolt the LCD in place using the supplied nylon M3 sized screws The nylon headers at the LCD module corners are a little longer than would be ideal Accordingl...

Page 61: ...nt the controls on a front panel The diagram shows the two buttons gain potentiometer and the rotary encoder PCB pads are also available for the microswitch Morse key as labelled in black bottom right...

Page 62: ...7805 voltage regulator requires no heatsink however the heat production will increase as supply voltage is increased and the IC does get uncomfortably hot to touch at 16V supply Although I still do n...

Page 63: ...n the display Select band 80m Turn the rotary encoder knob to select the band you have built the kit for Then press the small button to the left of the rotary encoder to make your selection There are...

Page 64: ...To do this give one long press to the left button The screen now displays the first menu category 1 Preset Turn the rotary encoder until you see the alignment menu 8 Alignment Now press the left selec...

Page 65: ...than one response of this simple band pass filter So tune the trimmer capacitor through its whole range and determine the maximum scaling factor that you see In my case here it is 09 Then make the ver...

Page 66: ...g for the MINIMUM amplitude not the maximum we adjusted the BPF trimmer to We adjust for minimum because now the injected signal is measuring the unwanted sideband We want to MINIMISE the unwanted sid...

Page 67: ...ite operating frequencies Each frequency preset can be edited in the configuration menu or loaded saved into from the currently operating VFO Message mode The firmware supports storage of 12 messages...

Page 68: ...configurable to your needs The battery voltage indicator would be useful if you intend to operate the radio portable on battery power Built in alignment tools One of the nicest features of this CW tra...

Page 69: ...se 4 characters display a basic and not calibrated S meter The scale is configurable see later description The S meter may be shown or hidden Battery voltage a battery icon appears to indicate the bat...

Page 70: ...radio that if you get into any unexpected function or menu you can nearly always press the right exit button to cancel and get back to the main operation mode Each of the buttons left centre right ma...

Page 71: ...start up is a configuration item in the VFO menu see later RIT can be easily adjusted during ordinary operation by double clicking the left button Now use the rotary encoder to tune the RIT As you do...

Page 72: ...individually edited in the Preset menu see later Often it is more convenient to just save them from the current VFO frequency To show the list of preset frequencies in normal operation mode double cli...

Page 73: ...ccording to the Repeats parameter in the Messages menu see later description The interval between the repeated transmissions is also defined in the Messages menu in the Interval parameter Once you hav...

Page 74: ...erating mode During viewing or editing of menu items the radio remains in receive mode on the currently selected VFO frequency The exception to this is certain alignment and test equipment tools where...

Page 75: ...13 the message repeat interval The underline cursor below the 4 indicates that editing is active turning the rotary encoder will change the parameter value When you are finished editing press the righ...

Page 76: ...cters 0 9 The CW decoder expects well timed CW with correct spacing between words and characters The CW decoder expects you to key in the numbers at near to the configured Keyer speed If you start key...

Page 77: ...ding the character which was originally in the current position Backspace delete If you select this character as the current character using the rotary encoder then when you press the left button the...

Page 78: ...cters text stored message 2 8 Message 8 50 characters text stored message 2 9 Message 9 50 characters text stored message 2 10 Message 10 50 characters text stored message 2 11 Message 11 50 character...

Page 79: ...eception Many of these parameters are only power up default parameters for the VFOs The current VFO frequency mode etc is not stored in these parameters If you wish to save the current VFO frequency m...

Page 80: ...r up The current RIT amount during ordinary operation is not stored in this parameter unless you Save settings as described previously 3 6 RIT rate 10 Hz This parameter specifies the RIT tuning rate a...

Page 81: ...en the received audio will fall outside the CW filter and be attenuated 3 9 Band 20m The chosen band configuration for your radio On first powering up the radio the display requests your selection of...

Page 82: ...smit or editing are commenced the speed is copied into the CW decoder and initialises it Thereafter if you transmit or enter data during editing at a different speed the CW decoder will adapt to your...

Page 83: ...r symbol spacing but it does not force you to wait for the correct duration of 3 dits between transmitted characters Some keyers do implement automatic character spacing such as the old 1973 Accu Keye...

Page 84: ...idetone is the audio tone which is generated by the microcontroller on key down and injected into the audio signal path Sidetone is ONLY an operator convenience to let you hear your keyed signal and h...

Page 85: ...detected or not Impulse noise that generates shorter pulses than the noise blanker parameter is ignored If the noise blanking period is too short then noise impulses will not be blanked effectively On...

Page 86: ...eter value is too high then it may take too long to adjust to the received station s amplitude resulting in missed characters while the decoder slowly adjusts itself It would also be too slow to autom...

Page 87: ...unction can also operate a CW beacon Weak Signal Propagation Reporter WSPR stands for Weak Signal Propagation Reporter It is digital message format filled with clever forward error correction The mess...

Page 88: ...longitude information parsed from the GPS serial data A WSPR transmission takes 1 minute and 52 seconds The GPS time and location data is parsed from the GPS serial data stream at the END of every WS...

Page 89: ...edu pulsar K1JT wspr html Below is a screenshot showing the WSPR 2 0 screen following reception of a few transmissions output frequency 1 500Hz Frame 02 Start 00 A number of other software packages ar...

Page 90: ...cording to the configured Keyer speed and with message start timing determined by the Frame and Start parameters see next sections WSPR the kit sends WSPR according to the configuration parameters in...

Page 91: ...04 If everybody transmits with 10 minute repetition rate starting on the hour then there will be bursts of activity every 10 minutes where everyone is transmitting at once and the potential for inter...

Page 92: ...key So you will need to enter the initial space character if required using the buttons and rotary encoder as discussed in the earlier section on editing TEXT parameters 6 7 WSPR locator IO90 The Loca...

Page 93: ...ws you to set the real time clock The clock setting takes effect and the seconds internally counted but not displayed are set to zero when editing of this menu is concluded either by pressing the left...

Page 94: ...tton all this time later 300 milliseconds after the first press then it means you executed a single long press c If you pressed the button again before the 300 milliseconds elapsed it is a double clic...

Page 95: ...ars 8 81V to 9 8V 1 bar 7 81V to 8 8V Empty 7 8V and below 7 5 Cursor style Underline Two different cursor styles are possible You can select your favourite here The two possible values are Underline...

Page 96: ...ent accidentally triggering this drastic step the factory reset is implemented as a virtual 2 digit numeric parameter To cause a reset Press the left select button to start editing this menu item 00 i...

Page 97: ...which the HIGH audio frequency 90 degree phase shift is performed 8 5 Ref frq 27 004 000 The reference frequency for the Si5351A synthesiser chip If you set this to the actual oscillation frequency o...

Page 98: ...ration tools to calibrate this value see below 8 7 Peak BPF Press Select Pressing the left select button activates the signal generator on the configured frequency and displays a bar on the screen sho...

Page 99: ...Adjustment and alignment at the end of the assembly part of the manual 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 co...

Page 100: ...ean invalid data 3D 3D fix could be None 2D or 3D f10 GPS solution fix uses 10 satellites t12 GPS receiver is tracking 12 satellites s30 average signal strength of the 12 tracked satellites is 30 The...

Page 101: ...V minus the voltage drop over the reverse polarity protection diode D3 9 2 RF Power 4 52 W This the RF Power meter function The measurable power range is 0 5W The RF power measurement circuit uses a s...

Page 102: ...frequency counter The resolution is 10Hz which results in an update rate of around 8 times per second approximately The frequency counter input is connected directly to the Timer1 input of the microc...

Page 103: ...he Si5351A Synthesiser chip datasheet maximum frequency specification is 200MHz However in practice it has been found to still operate reliably up to almost 300MHz The output waveform is a squarewave...

Page 104: ...front ends The detector has very high third order intercept IP3 and dynamic range as well as low loss The resulting I Q outputs are at audio baseband and go through a 90 degree phase shift network whi...

Page 105: ...QCX assembly Rev 1 08 105...

Page 106: ...duce the final output frequency The multiplication up and the division own are both fractional and so the frequency resolution is extremely finely controlled The chip has two PLLs and three output div...

Page 107: ...rly as you try to increase the reception frequency to cover higher bands For example on 10m e g 30MHz a local oscillator at 120MHz is required and the divide by 4 circuit must be able to operate at su...

Page 108: ...of the RF cycle each The result is that the audio difference beat between the RF input and LO input appears across each of the four integrating capacitors with four phases at 0 90 180 and 270 degrees...

Page 109: ...hase shift network and the first three op amps of the CW filter It is a great benefit not to have to AC couple each stage with coupling capacitors and then bias each stage individually In this circuit...

Page 110: ...d on the HI PER MITE CW filter kit design by David Cripe NM0S available from the Four State QRP group http www 4sqrp com HiPerMite php thanks David for permission to use it here This is a high perform...

Page 111: ...itched from transmit back into receive the mute switch needs to remain switched on for a short while after the receiver is switched back on A small wait while the thump subsides This delay is achieved...

Page 112: ...control line from the microcontroller is high the Clk2 signal is enabled as signal generator and routed via a 120K resistor straight to the RF input of the transceiver When the TX control line from th...

Page 113: ...u the required capacitance to bring it to resonance at the operating frequency Here we resort to experiment because it is a little difficult to know what the output capacitance of the transistor is Th...

Page 114: ...utput 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 la...

Page 115: ...key to ground But in our case the microcontroller implements automated stored message sending beacon modes and Iambic keyer so we need the microcontroller to be the boss of everything The microcontrol...

Page 116: ...of radio receiver projects that use the Si5351A report loud clicks every time the frequency is changed The cause of these clicks is one or both of two underlying issues a Faults in the software config...

Page 117: ...want a reduced brightness display you could increase the value of R48 Sidetone In this transceiver the sidetone is generated by Pulse Width Modulation using the ATmega328 s Timer1 peripheral The freq...

Page 118: ...umber of clicks of the rotary encoder and the direction the knob was turned in and at the same time debounce the switch transitions Another unnecessary component often seen is a pullup resistor on a s...

Page 119: ...he Transmit Receive switch must remain in transmit state for a short time after key up in order for the RF envelope of the key shaping circuit to drop gently down to zero which takes approximately 5ms...

Page 120: ...is would cause the transmitter to be keyed by the 1pps and serial data signals The 1K resistors protect the GPS outputs in case the paddles or onboard microswitch key inadvertently ground them The ATm...

Page 121: ...t damage altogether Perhaps don t feel tempted to try it intentionally Audio ADC There are two audio connections from the receiver signal chain to the microcontroller One is connected at the output of...

Page 122: ...1 5V and a high or 1 is greater than 3 5V Signal Generator The signal generator mode was also discussed in the operating manual section The signal output is simply taken from the Clk0 or Clk1 output...

Page 123: ...quad NAND gate is provided by IC11 a 7805 5V 1A voltage regulator Note that the input is protected against reverse polarity by D3 a Schottky diode type 1N5819 This also drops the voltage by 0 3 to 0...

Page 124: ...r T1 use the nomenclature indicated in the diagram right In many cases these measurements may not exactly match your own In particular if you use a power supply other than 12V then voltages which are...

Page 125: ...re the QSD integrating capacitors The voltage across each one differs slightly The following measurements show these small differences Top side of C44 2 44 Top side of C45 2 42 Top side of C46 2 30 IC...

Page 126: ...CD DB7 pin LCD pin 15 4 41 LCD backlight anode LCD pin 16 rightmost 0 00 LCD backlight cathode 6 5 RF Power output check If you go into menu 9 2 RF Power you can check your RF power output Your RF out...

Page 127: ...ult of the radio it is a consequence or limitation of the simple design When the LCD is updated by the microcontroller the activity on the signal lines to the LCD and in the microcontroller causes dig...

Page 128: ...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 12...

Page 129: ...The following charts show the power measurement using the oscilloscope to measure the peak peak amplitude across the 50 ohm dummy load Operation at output power levels above 5W is NOT recommended as i...

Page 130: ...The 40m band is shown Upon ignoring the ringing artefacts due to poor scope probes etc the waveforms are correct for Class E operation 7 5 RF envelope key shaping The following oscilloscope images sho...

Page 131: ...1 For each band one image shows the close in response the other shows the response across 0 to 30MHz Note that in the circuit the Band Pass filter sits behind the Low Pass filter Therefore the low pas...

Page 132: ...1 08 132 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 0...

Page 133: ...08 133 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...

Page 134: ...equency 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...

Page 135: ...SD does not significantly improve the selectivity of the CW filter but it does improve the intermodulation characteristics of the receiver 7 9 CW Filter response This chart shows the measured response...

Page 136: ...rves depend very heavily on the I Q balance and audio phase shift adjustments and these curves are from one measured prototype Subtraction of these two curves results in the unwanted sideband level as...

Page 137: ...enable Tx decoder 5 6 Enable Edit enable CW decoding during menu editing useful 6 Beacon 6 1 Beacon On Off enable beacon operation 6 2 Mode CW or WSPR 6 3 Frequency beacon frequency 6 4 Frame frame d...

Page 138: ...minor corrections 1 06 25 Sep 2017 Added instruction to insert short end of the pin headers into PCB Added C47 and other minor corrections to parts list 6 4 IC pin count is anticlockwise not clockwise...

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