[AMPS] coil form plastics

[Ian White, G3SEK]

Carl wrote:
>
>
>
>On Sun, 14 Feb 1999 11:28:09 +0000 "Ian White, G3SEK"
><G3SEK@ifwtech.demon.co.uk> writes:
>
>SNIP
>>
>>In the end, the only way to find out is to try it. For situations 
>>where
>>an inexpensive and easily machined material such as Delrin is proved 
>>to
>>work, there's no point in paying for PTFE or ceramic.
>
>B&W initially used ceramic forms for their 802 plate RFC. As a cost
>reduction they went to Delrin. I have several failed Delrin RFC's here
>that all failed at the tube end only which makes me believe it was a RF
>related failure, not DC or straight IR losses. 

Fair enough - anything involving high RF potentials (and probably high
temperatures too) is a risky application that would need careful testing
before committing to production. It's more difficult for component
manufacturers such as B&W and the roller coil makers because they can't
anticipate all future uses. 

It then comes back to the equipment manufacturers to test their products
well beyond the claimed ratings... but then the marketing droids want to
market the products at the test ratings! Finally the end users push the
products harder still, and sure enough, they fail.

>Soft Teflon makes a poor choke form but hard Teflon works quite well. I
>believe it has a fiberglass mixture. Machines well and costs less than
>pure Teflon.

Any brand names and sources?

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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