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Styrofoam coil form
5

Styrofoam coil form

Styrofoam coil form

(OP)
I have wound a coil on a styrofoam form.  Does anyone know of any issues with a styrofoam form?  I plan to use it in a device that is used outdoors.  It's Q will be 100 and low inductance.  It will also be part of a resonant circuit with circuit Q about 50.   

RE: Styrofoam coil form

Styrofoam melts at a low temperature.  If that isn't an issue it will probably work. (for a while)

Keith Cress
kcress - http://www.flaminsystems.com

RE: Styrofoam coil form

Doesn't styrofoam also have a memory problem?  Any pressure on it will cause a volumetric/density change, which could affect the net dielectric constant.

Why styrofoam?  It's not exactly a strength material.

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RE: Styrofoam coil form

Yeah it does.  It also comes apart eventually.  It also deforms to relieve any stresses.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Styrofoam coil form

(OP)
I can't really find a bobbin of the size I need. 1.2 x 4 inches.  Styrofoam is light weight, easily formed and low cost.  I need the induction field from it to induce a signal into a wire.  A 2 x 4 works, but I was afraid that it would absorb moisture.   I did notice the styrofoam compressing at the corners as I wound it.   

RE: Styrofoam coil form

As an alternative, how about composite deck boards?  They are avaliable at your local home improvement store and are a little more sturdy and weather resistant.  I think you can get it in the same dimensions as a standard 2x4 (1 1/2" x 3 1/2").   

RE: Styrofoam coil form

Styrofoam is mostly air. So much so that the dielectric constant appears to be near 1. In some RF and antenna tests I frequently use it to support cables or test items (all my work is at 3GHz or below). I've never seen it make more than a small fraction of a db difference.

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