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RE: [TCML] Coil forms, any good?

The only credible reported difference in secondary form materials so far as losses are concerned have been in the paper-based "Sonotube" concrete forms.  It wasn't the paper, it was the unknown binder that was believed to be responsible for the losses, and even then, the losses were theoretical based on (I think) ringdown measurements.  It was felt that such losses might only be an issue on CW or solid state coils.  The many, many pig-powered Sonotube coils that work just fine are evidence that it's not a deal breaker.

There was also a report that PVC pipe often contains random debris that in at least one instance, proved to be conductive, causing a secondary short.  PVC itself is just fine though.

I think there would be no measurable performance difference between the materials you mentioned.  I would base the choice on material strength, machinability, color (aesthetics), will glue and polyurethane stick to it, and weight.  I would choose the thinnest wall that's structurally adequate, but only to minimize weight.

Regards, Gary Lau

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Tesla
> Sent: Tuesday, January 15, 2008 1:59 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Coil forms, any good?
> Hi all.
> I have just struck a little bit of gold, I now have more or less
> unlimited supply of
> coil forms in glass fabric, cotton fabric and paper. The resin in
> these forms are some of the
> following: Phenolic, Epoxy, Melamine, Silicone and Polyester.
> Are they all good for winding coils on or are there some that i should avoid?
> Also if they're good, does the thickness of the wall(RF losses)
> affect the coil performance
> with these materials?
> Of course i have seen several on the web using fiberglass so i guess
> that should be ok
> but what about the other materials?
> Any input appreciated as i can get any diameter in any length for
> free. Lucky me....=)
> Thanks!
> /Matt
> www.tesla.nu (in Swedish)

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