OK, I've confirmed that if I Hide the Quisk window while running WSJTx (by minimizing it in the window manager), the problem completely disappears.
I think something in Quisk's display routines is starving other threads when it runs on the pi.
I think it's also causing some disruption to the WSJTX output as the power seems to fluctuate a little during the transmission.
It's possible something like this is also happening at other times, but as I said, CW operation seems normal, and I've made some SSB contacts as well and hadn't noticed it yet.
I don't know if there's a simple fix...
thanks,
Mario (AE0GL)
