Many thanks for the comments Robin & Allison,
G3PLX assumes audio frequency generation of the phase shift.
By generating the FT8 type frequency shift directly at RF it seems that the QDX is able to remove harmonics by using the RF low pass filters, rather than an audio frequency low pass filter and the linear following stages of SSB generation.
This is a brilliant system, one reason I got a QDX, for the idea alone, not because I particularly wanted to FT8 on 40m? :-)
(still interesting to try it out though)
Currently the QDX does not have the software ability to create a direct RF phase shift modulation, so psk31 is not possible, as Allison says.
However the Si5351a can be programmed to create a phase shift directly at RF.
In this case, perhaps the harmonics might also be removed by the RF low-pass filters, in the same way as for FT8.
("amplitude management" was definitely not the right way of expressing myself !)
Yes, i came up with this request due to seeing the post about FLDIGI, not sure what Mitch is doing, but I joined that group anyway :-)
Regards,? Ed? G8BQR
