The humble ATmega328 microcontroller, usually packaged as the Arduino Uno, is the entry-level vehicle for millions of people into the world of electronics and embedded programming. Some people just can’t miss the challenge of seeing how far they can push the old workhorse, and it looks like this [Guido PE1NNZ] is one of those. He managed to implement one Software-defined SSB amateur radio transceiver for the RF bands on the ATMega328, and it looks like the project is going to one place.
The radio started life as QRP Labs QCX, a $ 49 single band CW RF transceiver kit (Morse Code) that is already one of the cheapest ways to access the RF bands. [Guido] reduced the number of parts of the radio by about 50% and implemented much of the digital signal processing on the ATmega328. On the transmitter side, the SSB signal is generated by making minor frequency changes to a Si5351 clock generator using 800 kbit / s I2C and controlling a very efficient class E RF power amplifier with PWM for around 5W output power. The increased efficiency means that the bulky heat sink normally used in SSB radios is not needed. The radio is continuously tunable from 80 m to 10 m (3.5 MHz – 30 MHz), but requires plugging in a different low pass filter for each band.
The modified QCX is called QCX-SSB, but the project is evolving quickly with it [Guido] and a few others who are working on turning it into an entirely new radio called µSDX. Come on over to the Discussion group to stay updated. Currently, if you want to make your own, the easiest way is to purchase a QCX kit and use the instructions on the QCX-SSB Github repo to build it. Take a look at the overview below [Manuel DL2MAN]. The project is evolving at a rapid pace, however, and it is very likely that it will soon outgrow its QCX base and the ATmega328 that powers it.
This project could significantly reduce the technical and financial barrier to entry for new hams into the HF bands and we will definitely be monitoring this very closely. If you want to start with just one recipient, read this Multiband SSB capable receiver based on the Silicon Labs Si4735.