Rich said:
>This transformer needs to work at >150W.
They can be made to work at high powers, but not necessarily the 'stock' design,
as you say. Sevick is a good starting point for the theory. I think some his
designs were tested at high power. I do have a paper from a 1963 conference on
making 3-30 MHz xfmrs from 50 to 450 (or was it 600?) ohms which would do for
you, Rich - they were rated at 40kW for SWR <1.5:1!
Interestingly, they were 'conventional' transformers. They used 'tubes' of
ferrite, made up from individual toroid rings, like so many of the late Helge
Granberg's Motorola designs. They put sheets of aluminium between the rings to
act as cooling fins......
Of course, the easy way is to tune it with variable L and C......I suppose one
of the popular 'multiband one knob tuner' designs of the 1950's could be used,
although it's still another knob to turn.
73
Peter G3RZP
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