Guido PE1NNZ has modified a QCX transceiver to transmit SSB through a class E amplifier by using Envelope Elimination and Restoration, taking advantage of the atmega328 and the key shaping circuit. The built in DVM on the QCX is converted to take microphone inputs and there are minimal physical changes required. From Guido:
The SSB transmit-stage is implemented in a completely digital and software-based manner: at the heart the ATMEGA328 is sampling the input-audio and reconstructing a SSB-signal by controlling the SI5351 PLL phase (through tiny frequency changes over 800kbit/s I2C) and controlling the PA Power (through PWM on the key-shaping circuit). In this way a highly power-efficient class-E driven SSB-signal can be realized; a PWM driven class-E design keeps the SSB transceiver simple, tiny, cool, power-efficient and low-cost.
The code, mod instructions, and some basic measurements can be found here: https://github.com/threeme3/QCX-SSB