[Amps] Tufnol rod

[Ian White, G3SEK]

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