I've been trying, on and off, to make a QSO but the output power of the DDS is just too low to be heard. I'd just about given up until I managed to get an FT8 packet received by a station in Germany - about 900km away - on 20m. Not bad for 10mW or so...

I have one of those "45W amplifiers" (found cheaply all over the Internet) knocking around, so the next plan is to use it to boost the output of the DDS. First I'll tweak it slightly to bring the power down to 5-10W (the most I'm allowed on a Foundation Licence) and hopefully also lower the risk of popping the transistors.

I've also just realised that I can adjust the output power of the DDS chip by sticking a trimmer pot where Rset should go, giving a means of controlling the output of the PA once its connected.