The modest ATmega328 microcontroller, usually packaged as the Arduino Uno, is the drug for millions of people in the world of electronics and embedded programming. Some people just can’t take the challenge to see how far they can push the old workhorse and it looks [Guido PE1NNZ] is one of those. He was able to apply a software defined SSB radio for ham for the HF bands of the ATMega328 and the project seems to be going in places.
Radio began life as a QRP Labs QCX, a set for high-frequency CW transceiver (Morse code) for $ 49, which is already one of the cheapest ways to enter the HF bands. [Guido] reduce the number of parts of the radio by about 50% by implementing much of the signal processing digitally on the ATmega328. On the transmitter side, the SSB signal is generated by making slight changes to the frequency of a Si5351 clock generator using 800kbit / s I2C, and controlling a highly efficient Class E RF power amplifier with PWM for about 5W output power. The increased efficiency means that there is no need for the bulky radiator that is usually seen on SSB radios. The radio can be continuously tuned from 80m to 10m (3.5 Mhz – 30 Mhz), but requires the inclusion of different low-pass filters for each band.
The modified QCX is called QCX-SSB, but the project is rapidly evolving with [Guido] and several others working to turn it into an entirely new radio called the SDX. Log in discussion group to keep you informed. If you want to create your own, the easiest way right now is to take a QCX kit and build it using the instructions in the QCX-SSB Github repository. See the overview below from [Manuel DL2MAN]. However, the project is evolving rapidly and looks very likely to soon outgrow its QCX base and the ATmega328 that powers it.
This project could significantly reduce the technical and financial barrier for new hams to enter the HF bands and we will definitely follow it closely. If you only want to start with a receiver, check this out multiband receiver with SSB capability based on Silicon Labs Si4735.