I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Jimmie

"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use the
low viscosity resins sold in quarts, and not epoxy glues.

For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They are
extremely light with a specific gravity of 0.18 to 0.25 depending on the
manufacturer. Phenolic microballoons are also available.

For ultraviolet protection, a small amount of titanium dioxide may be added
(1 to 5%), but the microballoons will do a fair job alone. Painting the
finished insulators with acrylic paint (Krylon®) will also provide good UV
resistance.

Many marine supply stores carry these resins, the chopped fiberglass, and
the microballoons. Be extra careful with the polyester catalyst (typically
methyl-ethyl-ketone peroxide) as it is extremely damaging to the eyes.

Good luck with your project.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

NoSPAM wrote:
"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use
the low viscosity resins sold in quarts, and not epoxy glues.

For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They
are extremely light with a specific gravity of 0.18 to 0.25 depending on
the manufacturer. Phenolic microballoons are also available.

For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Many marine supply stores carry these resins, the chopped fiberglass,
and the microballoons. Be extra careful with the polyester catalyst
(typically methyl-ethyl-ketone peroxide) as it is extremely damaging to
the eyes.

Good luck with your project.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH

"Tom Donaly" wrote in message
...
NoSPAM wrote:
For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH

I was sent 10 pounds from a friend at DuPont, one of the larger
manufacturers of titanium dioxide. For small quantities, I would suggest
contacting a local paint manufacturer, or artist supply store. The pigment
is used in many ultra-bright white formulations. Note that titanium
dioxide has a high dielectric constant between 85 and 110 depending on the
ratio of rutile to anatase. So to minimize detuning effects of the
insulators, use them only at low impedance points of the antenna.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

On Sun, 25 Jan 2009 18:31:31 -0800, "Tom Donaly"
wrote:

NoSPAM wrote:
"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use
the low viscosity resins sold in quarts, and not epoxy glues.

For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They
are extremely light with a specific gravity of 0.18 to 0.25 depending on
the manufacturer. Phenolic microballoons are also available.

For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Many marine supply stores carry these resins, the chopped fiberglass,
and the microballoons. Be extra careful with the polyester catalyst
(typically methyl-ethyl-ketone peroxide) as it is extremely damaging to
the eyes.

Good luck with your project.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH
I use http://www.acp-composites.com/ACP-CAT.HTM

John Ferrell W8CCW

On Sun, 25 Jan 2009 20:46:28 -0500, "NoSPAM"
wrote:

For ultraviolet protection, a small amount of titanium dioxide may be added
(1 to 5%), but the microballoons will do a fair job alone. Painting the
finished insulators with acrylic paint (Krylon®) will also provide good UV
resistance.

I've never seen any white antenna insulators (except porcelain). Most
of the plastic antenna insulators I've seen are either black or
sometimes blue. I presume the filler and coloring used are something
something other than titanium white. Yet, everything made from marine
fiberglass is bright white, presumably doped with titanium white for
UV protection.

Is there any benefit to the white color over something like black
graphite stiffener and fill, which also offer UV protection? Duz the
color make any difference in preventing polymer chain breakage?

Drivel: I've noticed that the white PCV electrical tape I sometimes
use to wrap coax and connectors seems to last longer than the same
tape in black.



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

Jeff Liebermann wrote:
On Sun, 25 Jan 2009 20:46:28 -0500, "NoSPAM"
wrote:

For ultraviolet protection, a small amount of titanium dioxide may be added
(1 to 5%), but the microballoons will do a fair job alone. Painting the
finished insulators with acrylic paint (Krylon®) will also provide good UV
resistance.

I've never seen any white antenna insulators (except porcelain). Most
of the plastic antenna insulators I've seen are either black or
sometimes blue. I presume the filler and coloring used are something
something other than titanium white. Yet, everything made from marine
fiberglass is bright white, presumably doped with titanium white for
UV protection.

Is there any benefit to the white color over something like black
graphite stiffener and fill, which also offer UV protection? Duz the
color make any difference in preventing polymer chain breakage?

Drivel: I've noticed that the white PCV electrical tape I sometimes
use to wrap coax and connectors seems to last longer than the same
tape in black.

This is an interesting question. I have UV resistant rope that is black,
as well as UV resistant Ty-Wraps - also black in color. Wonder what the
deal is here?

- 73 de Mike N3LI -

Mike Coslo wrote:
Jeff Liebermann wrote:
On Sun, 25 Jan 2009 20:46:28 -0500, "NoSPAM"
wrote:

For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will
also provide good UV resistance.

I've never seen any white antenna insulators (except porcelain). Most
of the plastic antenna insulators I've seen are either black or
sometimes blue. I presume the filler and coloring used are something
something other than titanium white. Yet, everything made from marine
fiberglass is bright white, presumably doped with titanium white for
UV protection.
Is there any benefit to the white color over something like black
graphite stiffener and fill, which also offer UV protection? Duz the
color make any difference in preventing polymer chain breakage?

Drivel: I've noticed that the white PCV electrical tape I sometimes
use to wrap coax and connectors seems to last longer than the same
tape in black.

This is an interesting question. I have UV resistant rope that is black,
as well as UV resistant Ty-Wraps - also black in color. Wonder what the
deal is here?

- 73 de Mike N3LI -
Carbon black (and various other things) are also used as UV blockers.
Obviously, carbon black may not be the best thing for an insulator.
Sometimes it works, sometimes it doesn't. You have to test it.

"Jeff Liebermann" wrote in message
...
On Sun, 25 Jan 2009 20:46:28 -0500, "NoSPAM"
wrote:
For ultraviolet protection, a small amount of titanium dioxide may be
added
(1 to 5%), but the microballoons will do a fair job alone. Painting the
finished insulators with acrylic paint (Krylon®) will also provide good
UV
resistance.

I've never seen any white antenna insulators (except porcelain). Most
of the plastic antenna insulators I've seen are either black or
sometimes blue. I presume the filler and coloring used are something
something other than titanium white. Yet, everything made from marine
fiberglass is bright white, presumably doped with titanium white for
UV protection.

Titanium dioxide is a very bright white. It reflects the ultraviolet, as
well as visible and near-infrared. I am not familiar with its absorption
spectra in the far infrared. It is extensively used in marine fiberglass
resins, both for decorative and UV protection uses. Zinc oxide is also
white and it is used in sunscreens for the same reason.

The old Hy-Gain center insulators that were blue were likely polybutylene
terephthalate which is naturally UV resistant. The black insulators
contained carbon black, a UV absorber.

Is there any benefit to the white color over something like black
graphite stiffener and fill, which also offer UV protection? Duz the
color make any difference in preventing polymer chain breakage?

Carbon black is added as an absorber of ultraviolet. Graphite nanotubes
and graphite fibers are relatively recent developments. They are added to
produce a composite material which is quite strong and rigid in nature.
Being rather expensive compared to inexpensive carbon black, they are
generally added to plastics only for improved mechanical properties.

Polypropylene, Nylon, and Delrin absorb ultraviolet light and the energy
goes to breaking the polymer chain. Polybutylene and polyethylene
terephthalate absorb ultraviolet energy but fluoresce in the visible and
near infrared giving back the energy at a longer wavelength.
Polynaphthalene terephthalate is such a strong fluorescer in the visible
that it requires quenching additives in many applications such as food
packaging. Polyesters are used in marine ropes for their high strength and
UV resistance.

Drivel: I've noticed that the white PCV electrical tape I sometimes
use to wrap coax and connectors seems to last longer than the same
tape in black.

I would bet that red PVC tape lasts for only a short time in sunlight.
Most organic red pigments are destroyed rather quickly by ultraviolet
light, a real problem for automobile paint. There is a reason for Clear
Coat beyond its looks!

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

On Mon, 26 Jan 2009 22:26:58 -0500, "NoSPAM"
wrote:

Titanium dioxide is a very bright white. It reflects the ultraviolet, as
well as visible and near-infrared.
(...)
Carbon black is added as an absorber of ultraviolet.

So, the difference is that titanium dioxide reflects UV, while various
black pigments absorbs UV. Ok, that makes sense. Thanks.

I would bet that red PVC tape lasts for only a short time in sunlight.
Most organic red pigments are destroyed rather quickly by ultraviolet
light, a real problem for automobile paint. There is a reason for Clear
Coat beyond its looks!

Yep. One of my non-clever neighbors painted their house candy apple
red. Besides being rather garrish, the paint lasted about 2 years
before fading rather badly. They had to sandblast and re-prime in
order to start over with basic beige.

Incidentally, one of my former neighors was a painting contractor. He
painted his house with the left overs from various jobs. None of the
colors matched. Not exactly an eyesore, but close.

I have some red electrical tape. I'll give it a try on the roof and
let you know after summer.

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