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Chris Jones · December 6th 06, 09:43 PM posted to rec.radio.amateur.homebrew

wrote:

All,

I've been hearing how winding coils on discarded plastic pill bottles
is not suitable for RF tank circuits due to low Q, and that these would
not be safe for tube circuits anyway due to melting point.

I have access to kaolinite clay (white porcelain) and a kiln, and I was
wondering if I molded and fired this type of clay for coil forms, what
effect on a tank circuit Q this form would have.

Thanks in advance,

The Eternal Squire

Although the frequency is probably not the same as what you're going to use
the coils for, one way to test the loss of an insulator material is to put
some in the microwave oven (along with a mug of water to provide a load for
the magnetron). If the insulator material gets hot, then it is lossy. Of
course you would have to fire the clay before testing it, otherwise the
water content would make it get hot anyway.

If the pill bottles are polypropylene or a similar non-polar plastic then
they are probably not very lossy, but of course if the current through the
wire makes the wire hot by normal I^2*R losses, then the hot wire would
melt the plastic. This would only be a concern in a power amplifier or
tube circuits as you mentioned.

Chris