Hi, I have also been playing with this and have tried a type 61 transformer and another attempt at a 43 transformer with a different core with no improvement.
I built a copy of the PA on a separate board (not a PCB - point to point connections) driven by an Si5351 set with inverted outputs and obtained similar results.
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It is interesting to look at the gate drive voltage to the BS170 on a scope - in my case there is a big dip in the gate voltage so the BS170 are not fully turned on for the cycle.? I used a 350MHz Rigol and a homebrew active probe.? A normal 10x probe also showed the effect.? This dip appears on other bands as well but as the time period of the partial turn off is of lower percentage on the other bands the effect on output is reduced.? This dip is larger with the LPF connected to the output, but still present even when the output is connected directly to a dummy load, bypassing the pin diodes etc.
I tried removing one BS170 on each side so the one gate was driven by both outputs from the logic chip, this improved the gate waveform but the power out was low of course.
Hope this helps
Dave
M0WID
