Yes—an ATmega328P can generate single-sideband (SSB) signals through software, as demonstrated by the experimental QCX-SSB and uSDX projects. The microcontroller handles audio processing while a Si5351 clock generator and a class-E power stage produce the RF signal. The documented QCX-SSB implementation covers 160 through 10 meters and specifies up to 5 W PEP, but the design is experimental and those figures are not guarantees for every hardware or firmware version.
What “ATmega328 SSB SDR” means
The term refers to the QCX-SSB/uSDX line of experimental amateur-radio transceivers. Guido PE1NNZ adapted QRP Labs’ QCX CW transceiver so its ATmega328P could perform substantial SSB signal processing in software; the later uSDX project continues the architecture as an open-source design.
Calling it an SDR describes the software-based signal generation, not a promise that every part of the radio—including reception—is implemented digitally. In the documented transmit chain, the ATmega328P processes the microphone audio and controls RF generation. Hackaday’s 2020 report described the QCX-SSB modification as reducing the part count by about 50% while retaining a compact HF design. That is a historical description of the modification, not a measured comparison for every derivative.
How the ATmega328P generates SSB
- Audio sampling: The microphone signal enters the ATmega328P’s analog-to-digital converter. QCX-SSB firmware samples audio at about 4,800 samples per second.
- SSB processing: The firmware uses a Hilbert-transform-based complex-signal method to derive the phase information needed for single-sideband transmission.
- RF generation: Phase changes are translated into rapid frequency changes from a Si5351 clock generator, controlled over an 800 kbit/s I²C connection.
- Amplitude shaping: Pulse-width modulation controls the class-E power amplifier’s supply or key-shaping circuit so the transmitted envelope follows the audio.
This is a resource-constrained software-defined approach: an 8-bit microcontroller performs audio processing and coordinates the RF output rather than relying on a conventional SSB exciter and linear amplifier. The transmitter uses an efficient class-E RF power stage, not a conventional linear PA.
#1 Best Overall
- SSB reverse sideband/carrier suppression transmission: -45dBc, IMD3 (two tones) -33dBc, reception: -50dBc. Multi-band support, continuously adjustable in the 160m-10m frequency band (and performance loss from 20kHz to 99MHz). Open source firmware, built in for IDE; allows experimentation, can add new functions, can share contributions through Github, software complexity: 2000 lines of code.
- Simple, interesting and versatile QRP SSB HF transceiver with embedded and SDR functions. EER E-level driven SSB stage. 12V power supply provides about 5W Max PEP SSB output. Full mode support: USB, LSB, CW, AM, FM. filter: 4000, 2500, 1700, 500, 200, 100, 50Hz passband. function: automatic gain control (AGC), noise reduction (), voice trigger, voice trigger Xmit (), RX attenuator attenuator (ATT), TX noise gate, TX driver control, volume control, dBm/S-meter.
- This is a shortwave QRP SSB/CW transceiver. It boasts 1602 screen, built-in mic, built-in speaker! It can be connected to an automatic key, and can be decoded by CW. Using IRF series tube, . Can be used by connecting the antenna (BNC connector). 3 bands. Power standing wave digital display! Aluminum shell laser marking.
- Software-based can be used as a fast full invasive (QSK and semi-QSK operation), or to assist in running in digital mode (without CAT or PTT interface) for RX/TX switching, external PTT output with TX/PA control-delay. Simple installation modification with 8 component changes and 8 wires. , low-cost transceiver: Thanks to EER transmitter E-level, it has high power efficiency (no bulky heat sink required), and simple design (no need for complex balanced linear power amplifiers).
- SSB transmitter stage based entirely on digital and software: By controlling the phase of the SI5351 PLL (via the tiny frequency change of over 800kbit/s) and the amplitude of the PA (via the PWM of PWM) to sample the microphone input and reconstruct the SSB signal. PA key shaping circuit).
What the documented QCX-SSB implementation supports
| Capability | Documented QCX-SSB figure | Qualification |
|---|---|---|
| Band coverage | 160 m through 10 m, continuous tuning | LSB and USB modes; QCX-SSB project documentation |
| SSB bandwidth | Approximately 2,400 Hz | QCX-SSB project documentation |
| Transmit output | Up to 5 W PEP | QCX-SSB project documentation from the R1.01-era; not a guaranteed output for all builds |
| Operating features | Software break-in VOX; PC-assisted digital-mode support such as FT8 | Features described for the documented implementation |
These are project-specific documented capabilities, not specifications that automatically apply to every uSDX derivative, board revision, or firmware build. The project pages identify Guido PE1NNZ as maintainer.
What you need to build a QCX-SSB-style radio
- A QCX or compatible uSDX-style hardware platform.
- An ATmega328P controller and Si5351 clock-generator hardware.
- A microphone and the associated analog-input components.
- RF filters appropriate to the radio design.
- A class-E PA, suitable power system, and enclosure.
- An Arduino Uno for the documented firmware-upload process, or a compatible programming setup supported by the hardware.
- Assembly and test equipment appropriate for building and debugging an RF transceiver.
The required parts and exact assembly depend on the hardware revision. Schematics, firmware, layout files, and measurement notes are provided with the QCX-SSB project documentation; use the files for the specific version you are building rather than assuming parts or instructions are interchangeable across derivatives.
Rank #2
- "PIXIE" is mini the 40 meter band simple micro-power amplitude telegraph transceiver, 9 ~ 13.8V DC power supply
- Resistance to change is a horizontal packaging vertical packaging, easy to solve the short-circuit resistance has long been a problem.
- Power input does not distinguish between positive and negative, and to improve the power supply range, the user can easily use 13.8V communication power supply, and do not worry about the positive and negative reversed losses.
- Increasing the transmitter side as the buzzer sound prompts (using a jumper cap shielding sound), an increase of LED lights as transmitters prompt.
- You will receive the balun kits with the instructions.Or please contact the seller for the PDF instructions. Enjoy.Thx
How to convert or program a QCX for SSB
The project documents uploading the QCX-SSB sketch with an Arduino Uno and then placing or programming the ATmega328P. It does not establish one universal conversion procedure for every QCX board revision, so check the project schematic and firmware notes against your hardware before applying power.
- Confirm the hardware: Identify your QCX or compatible platform and verify that its schematic and board revision match the project files you plan to use.
- Gather the matching project files: Use the QCX-SSB sketch, schematic, layout, and measurement notes for that version.
- Upload the sketch: Follow the project’s documented Arduino Uno upload procedure. The documentation does not provide a universal command or Arduino IDE menu path applicable to every setup.
- Install or program the controller: Place or program the ATmega328P as specified for your hardware, then complete the required assembly and checks using the matching documentation.
- Test before operating: Verify the build and RF behavior using the project’s measurement guidance. Do not assume a successful firmware upload alone proves the transmitter is correctly assembled or aligned.
What to check before choosing a build
QCX-SSB and uSDX are best approached as experimental radio projects, not as interchangeable, fully specified commercial transceivers. Compare candidate versions on the points that affect your intended use:
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Rank #3
- LO Bands:80/60/40/30/20m，Mainboard：1.2 version,RF Board：1.0 version
- Assembled With Case:Out of box,Assembled with 3D printed case (orange),raised lettering.
- Already Bootloader:Mainboard have been finished the Bootloader and programed the firmware.The serial number has been attached to the bag inside the box.
- Call Sign:If you want to program your call sign, you need to read and fully understand the instructions which is in the package.
- Excluding Battery Case:If you want, you can see the Battery Case on another page.
- Supported bands and sideband modes for the exact firmware and hardware revision.
- Documented output power and the conditions or version attached to that figure.
- What is implemented in software and what the receive and transmit hardware requires.
- Firmware maturity and the completeness of the schematics, layout files, and measurement notes.
- Whether a compatible kit or assembled board is currently available in your region.
- How much RF alignment, troubleshooting, and test equipment the build requires.
Hackaday reported a QCX kit starting at $49 when its article was published in 2020. That is a historical price, not a current quote or evidence of present stock. Current availability and cost are not established by the project details summarized here.
Quick Recap
Best Value
- SSB CW Transceiver: This is a shortwave QRP SSB CW transceiver, can be connected to an automatic key and can be decoded through CW.
- Full Mode Support: The radio transceiver supports full mode of USB, LSB, CW, AM, FM DSP modes. Can be used to connect antennas (instrument base).
- Simple Installation: The transceiver greatly simplifies the original qcx circuit and reduces the installed components by 50%. No need for complex transformer windings and wiring procedures.
- Complete Accessories: This radio transceiver has a 1602 screen, built in battery, equipped with a charger, microphone, and built in speakers.
- Aluminum Shell: The radio transceiver adopts an aluminum shell, which has high strength, sturdy and long lasting.
Rank #4
- COMPLETE HAM RADIO FREQUENCY CHART IN YOUR POCKET 4 waterproof PVC cards with 8 pages of essential ham radio band plan data. Covers HF VHF UHF frequencies, Q codes, phonetic alphabet, RST signal reports, QRP calling frequencies, FT8 guide, antenna formulas and portable station checklist. Connected on a steel wire ring for easy carry in your go bag or scrub pocket.
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