Re: Tuning Primary

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello folks.

> We also need to tune like say +-10nF which is far greater than any
> varactor and most high voltage tuning caps...

The size problem was my first thought, too. But how about this one:
The old style variable cap from tube/valve radios, some have 2x500pF.
Not much, but with maybe ten of these ganged together, this could give
a pretty nice tuning range combined with a MMC.
Of course, these caps usually don't stand more than a few hundred volts,
maybe 1KV,,, dont really know, but under oil they should be able to run
a few KV. Pretty messy solutions, but might work for "online tuning".
Tuning by variable capacity would after all be more desirable than using
an external tuning coil.
But I still like Finn Hammers tunable primary most, very neat contruction
and the only one I have seen, that looks like the tapping point is able to
handle some current without problems.

best regards

Christoph Bohr