Hi Stefan,
Does the blue core become warm during operation?
No, it stays completely cold. Same for the two cores in the LPF.
How does the drain-voltage look like?
It is hard to describe and so far I am not able to provide a photo.
Not enough hands to hold probes and camera! I would say it is a
train of positive going pulses, rounded, not square, with some
ripple between (not a flat line between pulses). I will try to get a
photo in the next days.
It will run perfectly stable into the 50 ohm dummy load at 25 watts
output. Into the antenna it will do no better than 17 watts, usually
less before something goes wrong.
I think I am starting to understand what I am seeing. It looks to me
like a low frequency oscillation, well below the band, maybe at
audio. I do not yet understand why or how to stop it. I wonder if
putting a larger C in parallel to the 1 uF that bypasses the 68 ohm
resistor to ground would maybe do something? I will try it.
73,
Paul N1BUG
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