>
>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
>bubbling.
>
>>>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.
>
? Dissipation-factor provides a fair clue as to whether or not there is
likely to be a dissipation problem in the presence of RF.
>>> 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.
>
? Reduce the RF potential-gradient to a low enough value, and Nylon
makes an adequate RF insulating material. Zzzzzzzzz. Zzzzzz.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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