|From:||"John T. M. Lyles" <email@example.com>|
|Date:||Wed, 24 Mar 2004 10:37:30 -0700|
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. 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.
Cheers 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.?
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