[Amps] Re: insulation

[R.Measures]

>G10 will melt down into an awful stinkin' and 
>burnin' mess when heated in high Rf fields. I 
>rarely use it anymore, except for PW 
>applications. It is certainly a big step above 
>Delrin acetals or nylons. 

>From experience, G10 is ok for HF potentials of c. 6000V-rms.  

>Have settled on several 
>wonder materials like:
>Rexolite (crosslinked polystyrene) rod and sheet
>Polyetherimide (ULTEM* 2300) with 30% glass, also known as Tempalux*
>Polysulfone (UDEL*), also known as Thermalux*
>G7  (silicone resin reinforced glass)
>
>All more expensive, but if you want the highest Q 
>and no heating, they are worth it. These are all 
>high temperature engineered plastics. If you are 
>concentrating E field flux in the dielectric, 
>even with a kW, G10 will heat up. Good old UHMW 
>(ulta high molecular weight) polypropylene and 
>polyethyline made good insulators but have low 
>glass transisition temperatures and will soften 
>and dimensionally change with heat.
>
>Your local plastics supplier has them. Pricewise, 
>the first two are about $1000 for a square foot 
>of 1 inch thick material! The rod stock is much 
>cheaper, and for smaller coils it is more so. The 
>G7 is more difficult to machine or turn on a 
>lathe than G10 due to the lamination layers. But 
>it is excellent material structurally as well as 
>RF'ly.
>
Tnx, John - but you live in a taller forest than the rest of Hamdom.  


>John
>K5PRO
>
>Rich AG6K said:
>>  I bought 50-lbs of porcelain clay and I tried making porcelain
>>pottery.  The shrinkage factor is about double ordinary stoneware clay,
>>and porcelain clay is hellish to work with.  My advice is use G-10
>>fiberglass-epoxy for insulating.  It's good around RF, strong, and easily
>>drilled/machined. 
>>
>>>My YL has a ceramics business, and I started thinking about trying to
>>  >manufacture my own ceramic (porcelain) insulators. Has anyone tried this?
>