Reading uSDX and BitBanger firmware code to figure out the shape of the signal fed into the RF amplifier. It’s a square, but what's the voltage range?

They control “SI5351 PLL phase through tiny frequency changes” and “PA Power through PWM on the key-shaping circuit”, says PE1NNZ. Does that suggest for CW the CLK frequency and duty cycle are stable and I can concentrate on PB2's PWM thumb on the gate of the switch? https://github.com/threeme3/usdx #truSDX #uSDX #RFBitBanger #OpenResearchInstitute