Best plastic for antennas, machining
 

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 -

Best plastic for antennas, machining
 

On Aug 27, 12:10*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?

Polycarbonate, polycarbonate, polycarbonate.

It is way less brittle than plexiglass and far easier to machine and
work with.

It is a little more expensive than plexiglass.

Plexiglass is also know as acrylic. Polycarbonate is also known as
Lexan.

Polycarbonate is truly a wonderful material. I don't care what all
those people complaining about bisphenol-A say, polycarbonate is king.

Tim.

Best plastic for antennas, machining
 

On 8/27/2010 9:10 AM, 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 -



I have grown fond of nylon/teflon material, problem is, these materials
are difficult to find locally, and are expensive when found. In a
pinch, those plastic kitchen cutting boards are pressed into service
here. The are an opaque material, kind of "translucent white", softer
than plexiglass but hold up well under stress, will bend or warp rather
than break, seem to resist UV well enough, seem to exhibit good
insulation qualities up to VHF at least (highest freqs I have used them
at.) They can be cheaply had at used stores. They are usually 1/2
thick. Perhaps two sheets bonded or fastened together with brass/SS
hardware?

Regards,
JS

Best plastic for antennas, machining
 

John Smith wrote:
On 8/27/2010 9:10 AM, 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 -



I have grown fond of nylon/teflon material, problem is, these materials
are difficult to find locally, and are expensive when found. In a
pinch, those plastic kitchen cutting boards are pressed into service
here. The are an opaque material, kind of "translucent white", softer
than plexiglass but hold up well under stress, will bend or warp rather
than break, seem to resist UV well enough, seem to exhibit good
insulation qualities up to VHF at least (highest freqs I have used them
at.) They can be cheaply had at used stores. They are usually 1/2
thick. Perhaps two sheets bonded or fastened together with brass/SS
hardware?

Locally findable is good. I may pick up some and try some machining
experiments. Nylon is certainly tough. Thanks, John.

- - Mike -

Best plastic for antennas, machining
 

On Fri, 27 Aug 2010 09:16:57 -0700 (PDT), Tim Shoppa
wrote:

On Aug 27, 12:10*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?

Polycarbonate, polycarbonate, polycarbonate.

Fiberglass, fiberglass, and more fiberglass. It bends, it can easily
be repaired with a surfboard repair kit. It tolerates impacts better
than polycarbonate or plexiglass tubing. It's also UV resistant (when
coated with Krylon):
http://www.mgs4u.com/fiberglass-tube-rod.htm
$10 for 8ft of 1" plus shipping.

Polycarbonate is truly a wonderful material. I don't care what all
those people complaining about bisphenol-A say, polycarbonate is king.

There's some BPA in the epoxy resins used to bond the fiberglass matt
together. Don't drink out of your antenna, and you'll be fine.

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

Best plastic for antennas, machining
 

"Michael Coslo" wrote in message
...
John Smith wrote:
On 8/27/2010 9:10 AM, 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 -



I have grown fond of nylon/teflon material, problem is, these materials
are difficult to find locally, and are expensive when found. In a pinch,
those plastic kitchen cutting boards are pressed into service here. The
are an opaque material, kind of "translucent white", softer than
plexiglass but hold up well under stress, will bend or warp rather than
break, seem to resist UV well enough, seem to exhibit good insulation
qualities up to VHF at least (highest freqs I have used them at.) They
can be cheaply had at used stores. They are usually 1/2 thick. Perhaps
two sheets bonded or fastened together with brass/SS hardware?

Locally findable is good. I may pick up some and try some machining
experiments. Nylon is certainly tough. Thanks, John.

- - Mike -

Mike,
I use Delrin exclusively, great machining capabilities, and excellent RF
properties, very strong with excellent wear qualities, but make sure you use
the white product ONLY. If unsure, test it in the microwave on full power
for a minute along with a cup of water, and see whether it warms.

I have used it on all antennas from HF to UHF with no problems.
Use only 316 stainless steel hardware as well, less grief later on!
73
John VK2KC

Best plastic for antennas, machining
 

"Tim Shoppa" wrote in message
...
On Aug 27, 12:10 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?

Polycarbonate, polycarbonate, polycarbonate.

It is way less brittle than plexiglass and far easier to machine and
work with.

It is a little more expensive than plexiglass.

Plexiglass is also know as acrylic. Polycarbonate is also known as
Lexan.

Polycarbonate is truly a wonderful material. I don't care what all
those people complaining about bisphenol-A say, polycarbonate is king.

Tim.

Agree, Lexan is the way to go.
If it is good enough for the canopy of an F-16 it is just about good enough
for anything.

Sam - K7SAM

Best plastic for antennas, machining
 

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

--- news://freenews.netfront.net/ - complaints: ---

Best plastic for antennas, machining
 

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

Best plastic for antennas, machining
 

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