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Re: PVC w/ H2O

Original poster: Ed Phillips <evp@xxxxxxxxxxx>


Somewhere in the archives is a loss table for different types of coil forms.
I think maybe Richard Quick compiled them. I any case, PVC does become
pretty lossey in the high freq spectrum. My coil forms are coated 1/8" PVC.
I think the process of coating with polyurethane helps lesson the amount of
loss as well.

Polystyrene is very cheap for smallish coils and is very low loss if you are
in the high frequencies. I have a 4" form of this type for my future VTTC.

Regards and big Sparks,
Jim Mora"

The form contributes very little to the loss because the electric field between adjacent turns is small. As I mentioned earlier, I've used both white and grey PVC for coil forms up to 30 MHz and have never seen any evidence of excessive loss - Q's were quite high. As for polystyrene, be careful hitting it with most solvent-based varnish or the stuff mayl craze and you'll have a mess. Q-dope is intended for use with poly and works OK but it's expensive.