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[AMPS] coil form plastics

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Subject: [AMPS] coil form plastics
From: (Ian White, G3SEK)
Date: Mon, 15 Feb 1999 00:05:05 +0000
Rich Measures wrote:
>>Coming back to the roller coils, Rich makes a good point that *if* the
>>material has bubbled internally, that suggests internal RF losses as
>>well as external heating by contact with hot metal.
>?  Ian:  I did not and do not suggest that heat from contact with the
>wire causes any of the Delrin bubbling observed by users of MFJ tuners.

Yes, it is clear that external heating could not cause the internal

>>In the end, the only way to find out is to try it.
>?  I found out that Nylon, PVC, and Delrin had a Dissipation-factor
>problem by reading the specs. on them at the local plastics supply house.
But that tells you nothing about whether they will work well enough in a
particular situation. 

>> 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.
>?   There are many applications where Delrin would be better than PTFE or
>ceramic.  RF-applications is not one of them.  

As Dick has pointed out, there are many non-demanding RF applications
where Delrin can do the job adequately. For those applications, Delrin
works just as well as PTFE or ceramic would.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

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