Reg, Tarmo,

sorry for the delay, because I have been sick for a few days..

I am using some 3000 volts and some 300 volts screen-grid supply.
That should lead to some 5400 volts p-p

And yes, for the moment I am using L and c values comparable
to those mentioned by Tarmo. (designed for a loaded Q of around
12 as recomended by the ARRL handbook) However the inductor is
becoming quite hot, so I was wondering what could be done to
improve efficiency, without neglecting harmonic suppression.

I used Reg's program to recalculate things a couple of times
and to get a Q of around 12. However I could only realize this
by entering a phase-shift of about 90 degrees, which in turn
gave me the 'strange' C and L values...
However somehow (and do I feel stupid !) I do not succeed in
getting 'normal' values when using Reg's program....

Maybe his Q value is another value than mentioned by the ARRL ?

Arie.