Thanks Tobias and Stefan!

I ordered a few T130-2 and a couple of T200-2, should arrive
in time for next weekend.

Meanwhile, I rebuilt the filter using air cored coils and
it works great.  A lovely 200W sine wave into the dummy load
and nothing gets hot!  After a while the output transformer
is just slightly warm. DC in was 240W from a 60V supply and
it seems I don't need a cooling fan anywhere.

I turned the supply down to 10V and put a few volts of RF onto
the antenna (untuned) and got a bright line on Gary Taylor's
grabber - I was expecting a faint line!

A better RF ground is needed, there's some RF current going
to earth via the domestic ground which I'm not keen on.
So I'll put another transformer at the far end of the coax and
match the antenna/ground to its secondary.  I've run out of
toroid cores so it'll be lots of wire wound round a bucket.

That's the plan for today anyway, while the weather is good.
Maybe some transmission tonight if there's no VLF activity.

--
Paul Nicholson
--