Thanks for the suggestion George.? Common base presents an ideal low input impedance which is desirable.? What I am doing here is reproducing the G6LBQ design, which I assume has been built hundreds of times successfully. What is unique to my build is my board and layout, which could be the cause of many instability ills.??
That said, all of the tests above lead me to conclude that the problem is confined to the vicinity of Q5.? My construction is all SM on a hand made PCB, the layout separates output from input, and there is plenty of ground plane around and underneath the stage.? So it must be something else...
73 de VK3HN.?
Paul VK3HN