I am currently breadboarding the circuit as can be seen above and learning a lot about I2C communications programming. I have basic DDS software written and generating tones using the PWM functionality on the Uno and an external low-pass filter. I am now moving to a hardware DAC solution.
WSPR encoding and channel symbol generation code has been completed and verified against WSPRCode.exe available from Joe Taylor, the creator of WSPR so I am confident the WSPR generation bits are functional.
Initially, I am using my software DDS code to generate WSPR tones that could be then fed into an SSB transmitter. Longer term, I plan to use a hardware DDS to generate RF at the transmit frequency for stand-alone beacon use.