----- Original Message -----
From: "Jim Lux" <jimlux@earthlink.net>
>>
>>I use black PVC as coil forms at 1200 watts on 160
>>with no problems.
>
> Black PVC, or is it ABS DWV (drain, waste, vent), which is actually a
> foam core, and even lower effective dielectric constant. Although,
> being black, and pigmented with carbon, and foam cored, it makes a
> terrible insulator for HV use, particularly in electrostatic
> machines. But at the voltages you're likely to see in an antenna
> system, it should be fine. But in something like a Van deGraaff
> generator with a few microamps at 500 kV, it is horrible.
>
Solid Black PVC, not ABS DWV. My scientific material selection
process - found some laying on a shelf in the garage when I decided
to make the coils. So far no fires. The one at the base of the antenna
(I came up short on the center loading) shows absolutely no
discernable self-heating after a long period of high-duty cycle 1KW
CQing, so the unloaded Q of the inductor must be reasonably good.
73, Mike W4EF........................
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