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Add simplified instructions.

experimental
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@ -49,21 +49,13 @@ Below the schematic after the modification is applied, unused components are lef
## Installation:
For the modification, you need to remove 10 and change 8 components, install 8 wires, upload firmware and connect a microphone. On a newly to be build QCX, 71 components can be left out.
This modification consists of a few component changes and wires:
- **To simplify things, 78 components are no longer needed** (and you could omit them on an unbuilt QCX): IC6-10,R11-40,43,55,R59-64,C1,5,8,C9-28,C31,52,53,L1-3,D5,Q7,T1,JP1/DVM/FREQ.
- **SDR receiver**: change R7,10(82k); C4,C7(1nF), remove R11,12,14,15,17,27,29,59,IC10; wire IC2(pin15) to IC10(pin1); C39(R27/R29 side) to IC5(pin1); C40(IC10 side) to IC5(pin7), and disconnect R50(5V side) and R52(5V side) and wire both to IC2(pin21). Note on a QCX Rev5 you need to restore/insert manually the missing R49,50,53,C39 (see schematic). If you want to build-up the original (analog) QCX receiver, you can skip this step and insert a SPDT switch between C21(+ side) and IC9(pin1) for CW and R27(pin2) for SSB (as was done in [original QCX-SSB modification]).
- **SSB transmitter**: change D4,R56 (10k); R58 (.22uF); C32 (10uF), remove C31; wire IC2(pin21) to pin R57(side DVM-pin3); wire IC2(pin20) to DVM(pin2); wire IC2(pin18) to junction D4-C42-R58; install a microphone to tip (+ of electret) and sleeve GND of paddle-jack; PTT-switch to ring and sleeve ([X1M-mic]).
- **Multiband support**: remove C1,5,8,R64,T1; at T1 landing pattern (see [QCX Assembly instruction] T1) install R (1k) over 6-8; R (1k) over 3-4; C (10nF) over 4-8; C30 (30pF); L4 (1uH/16t); replace C25-28,L1-L3 with LPFs for different bands (e.g. [QRPLabs Low Pass Filter kit]).
Please note that if you apply the mod on a newer than QCX than Rev 4 (see the number on PCB in bottom right corner), you have in addition to convert back to the original Rev4 circuit (e.g. restore R49, R50, C39, R53, (C21, C22 excluded) on a Rev 5 PCB) See [PCB Revision] section and [QCX Assembly instruction] manuals for more info about the changes.
Change the following component values (and type of component in some cases), and wire the following component pins/pads:
1. To implement the SDR receiver: R11,12,14,15,17,27,29,59,IC10 (remove); IC6-10,R11-40,R43,R55,R59-64,C1,C5,C8,C9-24,C31,C52-53,D5,Q7,T1,JP1/DVM/FREQ (optionally omit on new builds); change R7,10(82k); C4,C7(1nF); wire IC2(pin15) to IC10(pin1); disconnect R50(5V side) and R52(5V side) and both wire to IC2(pin21); wire C39(R27/R29 side) to IC5(pin1); wire C40(IC10 side) to IC5(pin7).
_Rationale: This will feed the amplified I/Q signals to the ADC0, ADC1 input, biased at 0.5*VAREF, the rest of the receiver will be handled in software and audio output is realised on PB1._
To implement the original (analog) QCX receiver, you can skip this step and just brigde the CW-filter as was done in the [original QCX-SSB modification].
2. To implement the SSB transmitter: C31 (remove); change D4,R56 (10k); R58 (.22uF); C32 (10uF); wire IC2(pin21) to pin R57(side DVM-pin3); wire IC2(pin20) to DVM(pin2); wire IC2(pin18) to junction D4-C42-R58.
_Rationale: This will bias the mic input (at DAH line) with 5V and pass the audio to ADC2, biased at 0.5*VAREF; the key-shaping circuit is digitally switching the voltage supply to the PA (or alternatively directly controlled via PA bias<sup>[note 3](#note3)</sup>)._
3. Optionally, to implement multiband support: C1,C5,C8,T1,R64 (remove); at T1 landing pattern (see [QCX Assembly instruction] page 53) install R (1K) over 6-8; R (1K) over 3-4; C (10nF) over 4-8; C30 (30pF); L4 (1uH/16t); replace C25-28,L1-L3 with different LPFs as you wish (get some inspiration by [QRPLabs Low Pass Filter kit]).
_Rationale: The resonant elements and the transformer are replaced with a pass-through capacitor._
4. Upload the hex firmware-file to original or new ATMEGA328/328P chip (here is [latest released hex file] and click on "Assets" below the description). The [standard QCX firmware upload procedure] can be followed (for details <sup>[note 1](#note1)</sup>). The fuse settings should be E=FD H=D1 L=F7. After uploading, and the mods are applied correclt the display should show QCX-SDR (or QCX-SSB for the analog RX implementation).
5. Connect an electret microphone pins (+) to tip and (-) to sleeve of paddle-jack; PTT-switch pins to ring and sleeve (see [X1M-mic]).
**Firmware**: download [latest released hex file] and install with [standard QCX firmware upload procedure] (see also <sup>[note 1](#note1)</sup>).
Below the layout with components marked in red that needs to be changed; gray components must be installed and blank components may be omitted and some must be remove (see above):
![layout](layout.png)
@ -75,8 +67,8 @@ Below the wires that needs to be installed on the bottom PCB. Note that a circle
## Operation:
Currently, the following functions have been assigned to shortcut buttons (L=left, E=encoder, R=right) and menu-items:
| Menu Item | Function | Shortcut |
| ------------------- | -------------------------------------------- | -------- |
| Menu Item | Function | Button |
| ------------------- | -------------------------------------------- | ------ |
| 1.1 Volume | Audio level (0..16) & power-off/on | **E +turn** |
| 1.2 Mode | Modulation (LSB, USB, CW, AM, FM) | **R** |
| 1.3 Filter BW | Audio passband (Full, 300..4000, 300..2500, 300..1700, 200, 100 Hz) | **R double** |
@ -114,11 +106,11 @@ There is a menu available that can be accessed by a short left press. With the e
For receive, by default an AGC is enabled. This increases the volume when there are weak signals and decreases for strong signals. This is good for SSB signals but can be annoying for CW operation. The AGC can be turned off in the menu, this makes the receiver less noisy but require more manual volume change. To further reduce the noise, a noise-reduction function can be enabled in the menu with the NR parameter. To use the available dynamic range optimally, you can attenuate incoming signal by enabling a front-end attenuator with "ATT" parameter. Especially on frequencies 3.5-7 MHz the atmospheric noise levels are much higher, so you can increase the receiver performance by adding attenuation (e.g 13dB) such that the noise-floor is still audible. To calibrate the transceiver frequency, you can tune to a calibrated signal source (e.g. WWV on 10 MHz) and zero-beat the signal by changing "Ref freq" parameter; alternatively you can measure the XTal frequency with a counter and set the parameter. A S-meter of choice (dBm, S, S-bar) can be selected with the S-meter parameter. Selecting an S-bar, shows a signal-strength bar where each tick represents a S-point (6dB).
For SSB voice operation, connect a microphone to the paddle jack, a PTT or onboard "key" press will bring the trasnceiver into transmit. With the "TX Drive" parameter, it is possible to set the mdulation depth or PA drive, it is default set to 4 increasing it gives a bit more punch (compression for SSB). Setting it to a value 8 in SSB means that the SSB modulation is transmitted with a constant amplitude (possibly reducing RFI but at the cost of audio quality). To monitor your own modulation, you can temporarily increase MOX parameter. A long press on the right button enters the transceiver in VOX operation, the VOX sensitivity can be configured in the menu with "VOX threshold" parameter. The PA Bias min and max parameters sets the working range of the PWM envelope signal, a range of 0-255 is the full range which is fine if you use a key-shaping circuit for envelope control, but when you directly bias the PA MOSFETs with the PWM signal then you specifiy the optimal working range from just above the MOSFET threshold level to the maximum peak power you would like to use (0-180 are good values on my QCX).
For SSB voice operation, connect a microphone to the paddle jack, a PTT or onboard "key" press will bring the trasnceiver into transmit. With the "TX Drive" parameter, it is possible to set the mdulation depth or PA drive, it is default set to 4 increasing it gives a bit more punch (compression for SSB). Setting it to a value 8 in SSB means that the SSB modulation is transmitted with a constant amplitude (possibly reducing RFI but at the cost of audio quality). To monitor your own modulation, you can temporarily increase MOX parameter. A long press on the right button enters the transceiver in VOX operation, the VOX sensitivity can be configured in the menu with "VOX threshold" parameter. The PA Bias min and max parameters sets the working range of the PWM envelope signal, a range of 0-255 is the full range which is fine if you use a key-shaping circuit for envelope control, but when you directly bias the PA MOSFETs (<sup>[note 3](#note3)</sup>) with the PWM signal then you specifiy the optimal working range from just above the MOSFET threshold level to the maximum peak power you would like to use (0-180 are good values on my QCX).
For FT8 (and any other digital) operation, select one of the pre-programmed FT8 bands by double press the rotary encoder, connect the headphone jack to sound card microphone jack, sound card speaker jack to microphone jack, and give a long press on right button to enter VOX mode. Adjust the volume to a minimum and start your favorite FT8 application (JTDX for instance). The sensitivity of the VOX can be set in the "VOX threshold" parameter.
On startup, the transceiver is performing a self-test. It is checking the supply and bias voltages, I2C communications and algorithmic performance. In case of deviations, the display will report an error during startup. It also discovers the capabilties of the transceiver depending on the mods made. The following capabilities are detected and shown on the display: "QCX" for a QCX without mods; "QCX-SSB" for a QCX with SSB mod; "QCX-DSP" for a QCX with SIDETONE disconnected an connected to a speaker; "QCX-SDR" for a QCX with SDR mod. Please check if the this capability matches with the mods.
On startup, the transceiver is performing a self-test. It is checking the supply and bias voltages, I2C communications and algorithmic performance. In case of deviations, the display will report an error during startup. It also discovers the capabilties of the transceiver depending on the mods made. The following capabilities are detected and shown on the display: "QCX" for a QCX without mods; "QCX-SSB" for a QCX with SSB mod; "QCX-DSP" for a QCX with SIDETONE disconnected and connected to a speaker (through decoupling capacitor); "QCX-SDR" for a QCX with SDR mod. Please check if the this capability matches with the mods.
## Technical Description:
@ -157,7 +149,7 @@ The following performance measurements were made with QCX-SSB R1.01, a modified
- [AVRDudess] tool or avrdude CLI (avrdude -c avrisp -b 19200 -P /dev/ttyACM0 (or: /dev/ttyUSB0) -p m328p -e -U efuse:w:0xfd:m -U hfuse:w:0xC1:m -U lfuse:w:0xF7:m -U flash:w:firmware.hex) can be used for uploading the firmware via the ISP connector on the QCX. Follow [Arduino as ISP] instructions if you have a Arduino UNO board available (tip: use female-to-male breadboard cables to connect Arduino to QCX ISP jumper); or [USBasp] instructions if you have a USBasp programmer, alternatively use [USPasp ExtremeBurner]; but many other ISP programmers can be used in similar manner such as [USBtiny] or AVRisp mkII. During ISP, mic should be disconnected, power supply should be connected; in tool do not erase, program EEPROM or set fuse settings (they are by default ok: E=FD H=D1 L=F7).
- Alternatively, in case you have an ATMEGA328P chip with Arduino bootloader, you can place the chip in an Arduino UNO board and upload directly (without the need for a ISP cable and QCX) by specifying 'arduino' programmer and baudrate 115200.
- Alternatively, in case you have an [Arduino 1.8.9] (or newer) environment installed, you can upload the [QCX-SSB Sketch] directly from the Arduino environment (without using AVRDudess and firmware file); make sure "Tools > Board > Arduino/Genuino Uno", "Tools > Port > /dev/ttyUSB0 or ttyACM0", and then "Sketch > Upload" is selected, while the ATMEGA328P chip is placed in the Arduino UNO socket. It is also possible to use [Arduino as ISP] method: upload this variation of [ArduinoISP] to the Arduino board and select "Tools > Programmer > Arduino as ISP", and "Sketch > Upload Using Programmer".
2. <a name="note2"/>The occupied SSB bandwidth can be further reduced by restricting the maximum phase change (set MAX_DP to half a unit-circle _UA/2 (equivalent to 180 degrees)). The sensitivity of the VOX switching can be set with parameter VOX_THRESHOLD. Audio-input can be attenuated by increasing parameter MIC_ATTEN (6dB per step).
2. <a name="note2"/>The occupied SSB bandwidth can be further reduced by restricting the maximum phase change (set MAX_DP to half a unit-circle _UA/2 (equivalent to 180 degrees)). Audio-input can be attenuated by increasing parameter MIC_ATTEN (6dB per step).
3. Alternatively, the PA MOSFETs can be directly biased by the PWM envelope signal, basically making the key-shaping circuit redundant. To do so, Q6,Q4,R41,R42,C32,C31 can be removed entirely, whereby C-E pads of Q6 are wired, and where a 100nF capacitor is inserted at IC3A-pin3 and G of Q1-3, and where a 10k resistor is placed at G-D pads of Q4, a 10nF capacitor between S-D pads of Q4, and where a 10k resistor is placed between D of Q4 and G of Q1-3.