Material for coil bobbins?

[Yorkie]

To an extent it depends on the frequency the coil will operate at. Some plastics become lossy at higher frequencies - especially black plastics as they may have carbon in them. I read a useful tip some years back about testing coil formers for use at VHF/UHF. Put it in a microwave oven for a couple of minutes with a glass of water alongside to absorb some of the microwave energy. Remove the coil former and see it it's heated up much. If it hasn't then clearly its good at microwave frequencies so will pose no problems at lower frequencies.

I'd have thought that polycarbonate, acrylic, acetal, delrin, tunol, paxolin (or other phenolic resin) tubing would be fine. Trouble is that most suppliers seem to want to sell it in 2M lengths, but some will cut it down to your sizes. Though you don't mention any diameter John, if for example, if you wanted 20mm external/14mm internal, this outfit sell acrylic tube (as well as lots of other sizes, shapes colours etc) and would no doubt cut it into ten 200mm lengths for postage.

http://www.plastock.co.uk/Tube/Round/Acr...-p348.html 20mm OS 14mm ID £10.01GBP

(Don't know the shipping situation from UK to CH - if you do spot anything from UK suppliers who won't ship it to you, I'd be happy to get it and forward it on).

Hope that helps a bit.