[Amps] Delrin in RF Fields

[R.Measures]

•  Jim --  Delrin® was used for the roller-coil form in an MFJ "3kW" 
antenna tuner.  During testing at c. the 1kW level in the ARRL lab, the 
roller coil form reportedly melted and  ignited.  The problem is that 
Delrin® has a worrisome D-factor at 1MHz, and the problem worsens as f 
increases.  ABS, or any of the other styrenes, has a lower D-factor.   (I 
found this info out at a local  plastics dealer).  Sure, ABS isn't as 
nice to machine as Delrin®.. 

>
>Gentlemen (and all ladies!),
>
>After watching the "thread" on insulation, and the comments on DELRIN and 
>its generics, I seemed to recall the use of DELRIN for RF Plate choke 
>forms in the past.  Here is an example from PW DAHL's On-Line store:
>
>http://pwdahl.com/cgi-bin/store/commerce.cgi?product=rfchokes&cart_id=9228
>764.5624
>
>
> What are the risks here? 
>
>Jim W6JNG
>
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