On 08/27/2010 01:10 PM, Michael Coslo wrote:
Afternoon everyone,

I'm rebuilding my Bugcatcher antenna. It works well, but the XYL had a
bit of an accident last year when we had a big snowstorm, the leaves
weighted down the limbs, and the antenna, which was strapped down, still
managed to introduce itself to a limb.

Anyhow, the original antenna was mounted using 1 inch thick plexiglass,
with holes drilled to run the mast through, and tapped screw holes to
mount to the back up plate, in turn mounted to the spare tire holder.

I'm trying to make something a little prettier now that I'm rebuilding it.

But the thing is, I'm curious about the material. Is there any
particular material to avoid? I know Plexi works, but what about PVC?
Delrin? Bondo? 8^) Miiling, water absorption, etc?

- 73 de Mike N3LI -

Somewhere I read not to use PVC for coil forms. Is it so ?


--
Alejandro Lieber LU1FCR
Rosario Argentina

Real-Time F2-Layer Critical Frequency Map foF2:
http://1fcr.com.ar

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On 8/28/2010 9:44 AM, Alejandro Lieber wrote:

...
Somewhere I read not to use PVC for coil forms. Is it so ?

Having used it, I don't know why that statement would be made ... I have
heard the same about PVC grey conduit, and wonder who has tested it and
what problems they found ...

Regards,
JS

On Sat, 28 Aug 2010 13:44:24 -0300, Alejandro Lieber
wrote:

Somewhere I read not to use PVC for coil forms. Is it so ?

http://www.tangram.co.uk/TI-Polymer-PVC.html
Electrical properties
The insulation properties of rigid PVC are satisfactory and
those of plasticised PVC are poor. The values, which are
only mediocre in any case, are impaired still further by the
plasticisers. As a result of the high dissipation factor,
PVC is not suitable for high frequency applications.

PVC has a dissipation factor of about 0.0350 compared to about 0.00610
for Polycarbonate.
http://www.matweb.com

Black PVC is also loaded with a small amount of carbon pigment, which
likes to get warm/hot/melt when RF is applied.

PVC is also subject to dielectric absorption. Build a capacitor out
of two plates with some PVC in between. Apply some DC, remove the
power source, and short the plates for 2 seconds. Then measure the
residual voltage across the plates. PVC and vinyl are awful. Teflon,
polystyrene, and polypropylene don't have this problem.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS