The AD9850 module arrived today, so I quickly set about hooking it up to the Arduino. A few wires and a few lines of (stolen) code later, and I had it producing CW.
Then it was an easy step to integrate it with the frequency estimator code from yesterday, and hey presto!
Here's a pic:
Using a .wav file recording of FT8 audio, I was able to produce a real FT8 transmission (on 14MHz) and JTDX was able to receive and decode it - worked first time. Not only that but my 'blob' on the waterfall looked just like everybody else's, suggesting that the RF spectrum being produced is nice and clean.
Now let's remember, the output power is very feeble (only a few milliwatts), and I have no antenna connected yet, so there's still work to do...