G3RZP wrote:
Has anyone had any experience with the machinable ceramics now
available e.g. from Farnell in the UK? They look ideal for a lot of
amps applications, although rather expensive.
If they're like the ones I used in the lab some years ago, they're death
to lathe tools (the dust isn't so good either) and they still need to be
fired to full hardness.
Rich comments on the cold flow of Teflon/PTFE. It can be a problem, but
may be manageable if there's not too much stress.
Which there shouldn't be, in an RF choke wound on something like 3/4in
solid rod.
Fibreglass tube is the best bet, although it too may be a bit
hygroscopic.
Pyrex glass tubing is also good, though it's difficult to anchor the
ends of the winding. To make a base mounting, epoxy in a large brass
nut.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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