Shellac, varnish, parrafin wax for wood feedline spacers?
Tim Shoppa
ladder-line spacers cut from polycarbonate sheet. Works great, is
kinda pretty in the right light. The polycarbonate is supposed to be
relatively UV-resistant and it seems to be doing pretty good.
But I have a hankering to use wooden insulators next time I put an
antenna up.
The old ARRL handbooks always recommended boiling wooden feedline
spacers in paraffin wax for weatherproofing. I suppose the idea is
that it's water-repellent. Don't know how long this can be expected to
survive weather extremes (ice, heat). In my experiments in my garage,
the wax coating seems to pretty much rub right off with my fingernail,
so I'm not sure how much good it does where the feed wires or tie
wires abrades against it.
Shellac is another option I suppose, but shellac seems to me to be
something like the enamel coating on magnet wire, and having used this
in rooftop antennas in the past I was quite surprised that in the
summer it gets hot enough up there to burn off the enamel.
Spar varnish seems to be the ultimate in wood coatings for weather
resistance.
Any words of wisdom? Or is polycarbonate really the cat's meow?
Having fabricated antenna stuff out of both plexiglass and
polycarbonate over the years, I am very very impressed with
polycarbonate's workability. It does not craze or crack the way that
plexiglass does.
Tim N3QE
Hal Rosser
> The old ARRL handbooks always recommended boiling wooden feedline
> spacers in paraffin wax for weatherproofing. I suppose the idea is
> that it's water-repellent. Don't know how long this can be expected to
> survive weather extremes (ice, heat). In my experiments in my garage,
> the wax coating seems to pretty much rub right off with my fingernail,
> so I'm not sure how much good it does where the feed wires or tie
> wires abrades against it.
I think if you're using an older transmitter - keep up the retro theme by
boiling the wood spacers in parafin like the old book says. (But I would
bake them at 190degrees for an hour to remove all moisture first.)
I would also be tempted (considering your home-making the feed line anyway)
to try what I recall being called "G-line", where on the transmitter end of
the line you keep increasing the spacing then just drop one line - and you
have only one conductor going up.
then of course, you do the same thing at the antenna end, going from
2-conductoe wide spacing to 'normal spacing'.
Experiment.
Report back on how it went.
lt...@yahoo.com
Any of the above. Best? Which lasts longer? Which would you
rather use? What's the difference? Not much.
Have fun.
- 'Doc
Roy Lewallen
flammable -- I'd guess about like gasoline -- so be extremely careful if
you use the old time method. At the very least I'd do it outside and
over an electric hot plate rather than an open flame.
Roy Lewallen, W7EL
NoSPAM
problems.}
"Hal Rosser" <hmro...@bellsouth.net> wrote in message
news:4G6Sk.59158$kh2....@bignews3.bellsouth.net...
> I think if you're using an older transmitter - keep up the retro theme by
> boiling the wood spacers in parafin like the old book says. (But I would
> bake them at 190degrees for an hour to remove all moisture first.)
>
> I would also be tempted (considering your home-making the feed line
> anyway) to try what I recall being called "G-line", where on the
> transmitter end of the line you keep increasing the spacing then just drop
> one line - and you have only one conductor going up. then of course, you
> do the same thing at the antenna end, going from 2-conductor wide spacing
> to 'normal spacing'.
G-line, more correctly known as Goubau line, is not practical for use in the
HF range. It is generally limited to UHF frequencies and above due to the
physical size of the "launchers" which generate a surface wave along the
line. For details, see: Geog Goubau, "Surface waves and their Application
to Transmission Lines," Journal of Applied Physics, Volume 21, Nov. (1950).
What I believe Hal is talking about was the early practice of using a single
wire from the transmitter to connect to an essentially horizontal antenna.
Of course that single wire did not behave as a transmission line, but rather
became part of the antenna working against ground. In many cases this wire
became the actual antenna with the horizontal portion acting as capacitive
loading. The resulting antenna pattern is often quite distorted from that
expected of the dipole. A good ground is needed on the transmitter, yet
problems of RF in the shack are common.
If you do decide to use wood spacers, acrylic urethane varnish applied to
dry wood will last the longest and have the best ultraviolet resistance.
Shellac, a natural product, actually has a surprisingly good ultraviolet
resistance too. While boiling the wood in paraffin wax is authentic, be
very careful as Roy, W7EL, points out. The flash point of typical paraffin
wax is approximately 380 to 390 F. Use a double boiler with water in the
lower boiler to melt the wax keeping it well below the flash temperature.
Be very careful as the hot wax causes very bad burns. Work outdoors and
keep a fire extinguisher handy. If you have a local source of bamboo,
consider using it as it is light and often free.
I have made open wire line using poly(ethylene terephthalate) tensile test
bars liberated from the trash where I worked. These PET "dog biscuits"
worked well in this application as PET has good resistance to UV and is
extremely tough.
73, Barry WA4VZQ
Hal Rosser
the increasingnes of the spacing of the conductors go into multiple
wavelengths, which as you reminded us, is not practical for HF frequencies.
But for 2-meters and above, it may be worth a try.
The Bamboo suggestion sounds good, by the way. I used to use 300-ohm
twinlead because of the light weight because I wanted the antenna up as high
as possible, and more weight made it droop.
"NoSPAM" <unk...@nospam.org> wrote in message news:gfg2gl$igp$1...@aioe.org...
> {Note: I tried posting this yesterday but Charter's NNTP server was having
> problems.}
>
> G-line, more correctly known as Goubau line, is not practical for use in
> the
> HF range. It is generally limited to UHF frequencies and above due to the
> physical size of the "launchers" which generate a surface wave along the
> line. For details, see: Geog Goubau, "Surface waves and their Application
> to Transmission Lines," Journal of Applied Physics, Volume 21, Nov.
> (1950).
>
> What I believe Hal is talking about was the early practice of using a
> single
> wire from the transmitter to connect to an essentially horizontal antenna.
> Of course that single wire did not behave as a transmission line, but
> rather
> became part of the antenna working against ground. In many cases this
> wire
> became the actual antenna with the horizontal portion acting as capacitive
> loading. The resulting antenna pattern is often quite distorted from that
> expected of the dipole. A good ground is needed on the transmitter, yet
> problems of RF in the shack are common.
>
> 73, Barry WA4VZQ
>
>
>
>
co_f...@yahoo.com
>
> But I have a hankering to use wooden insulators next time I put an
> antenna up.
>
> The old ARRL handbooks always recommended boiling wooden feedline
> spacers in paraffin wax for weatherproofing. I suppose the idea is
> that it's water-repellent. Don't know how long this can be expected to
> survive weather extremes (ice, heat). In my experiments in my garage,
> the wax coating seems to pretty much rub right off with my fingernail,
> so I'm not sure how much good it does where the feed wires or tie
> wires abrades against it.
>
Hi.
I think some Thompson's water seal would be a good substitute for the
boiling paraffin wax. I think the Thompson's is wax dissolved in
kerosene or Diesel. I have been putting two coats on some posts going
into the ground.
Paul
John Smith
> ...
> Shellac is another option I suppose, but shellac seems to me to be
> something like the enamel coating on magnet wire, and having used this
> in rooftop antennas in the past I was quite surprised that in the
> summer it gets hot enough up there to burn off the enamel.
>
> Spar varnish seems to be the ultimate in wood coatings for weather
> resistance.
> ...
> Tim N3QE
If those ancient OT's heard you state the above, after desiring
materials better than dehydrated wood with hydrocarbons for
preservatives, as their insulators ... well, just suffice it to say,
they'd strike you up the side of the head, HARD! <grin>
Regards,
JS
ml
"Hal Rosser" <hmro...@bellsouth.net> wrote:
find some of that oil they soak telephone poles in then coat it
w/sealer
ultimately wood prob wont last as long as some good plastic and
i guess would be heaver stressing the wires more
it will prob still hold more water than a smooth plastic dunno
and prob not have as good insulative prop's but might be moot
NoSPAM
"ml" <m...@di.net> wrote in message
news:m-540259.05...@news.optonline.net...
> In article <MbMSk.2377$Lv6....@bignews8.bellsouth.net>,
> "Hal Rosser" <hmro...@bellsouth.net> wrote:
>
>> Thanks, Barry on helping to wake up my recollections. I had forgotten
>> that
{snip}
> find some of that oil they soak telephone poles in then coat it
> w/sealer
>
> ultimately wood prob wont last as long as some good plastic and
> i guess would be heaver stressing the wires more
>
> it will prob still hold more water than a smooth plastic dunno
>
> and prob not have as good insulative prop's but might be moot
I consider this a poor suggestion for a number of reasons...
Several methods of wood treatment have been used over the years. The three
main methods used to be pressure treatment with creosote, pentachlorophenol,
or inorganic arsenic salts. These were generally replaced by chromated
copper arsenate. Other treatments involved copper napthenate, zinc
napthenate, and tributyl tin oxide. All of these methods provide fungus
protection and some limited moisture protection.
Creosote, as used for treating wood, is generally coal tar creosote. This
material is distilled from coke oven tar and it contains polycyclic aromatic
hydrocarbons, phenols, and cresols, all of which are quite toxic and most
are either proven or suspected carcinogens.
Pentachlorophenol is registered by the Environmental Protection Agency as an
insecticide (termicide), fungicide, herbicides, molluscide, algaecide,
disinfectant, and as an ingredient in antifouling paint. Stated simply. it
is toxic to just about all life.
Chromated copper arsenate, at one time, was the most widely used wood
treatment. Hexavalent chromium and arsenic in any form are both extremely
toxic, so newer treatments were developed including ammoniacal copper
quaternary. The EPA lists this as a general use pesticide and it is far
less toxic than chromated copper arsenate. Other newer wood treatments used
today are based on borax and other borate salts. These too are less toxic
than the older copper salts.
The oil treatment that "ml" refers to is most likely creosote. However
creosote or any other of the treatments described above will not make the
wood a good electrical insulator for use as spacers in open wire
transmission line. Raw wood or wood treated with any of the metal salts
shows a high dielectric loss. Even pentachlorophenol is not very suitable
as its dielectric constant is around 8 to 10. But then the wood itself
usually has a radio frequency dielectric constant around 10 or more too,
even if completely dried. Increases are seen at frequencies below the MHz
region, and with increasing moisture. The loss tangent of wood also
increases rapidly with moisture content.
The reason that old timers boiled their wood dowels in paraffin wax was
twofold. The first was to completely dry the wood, and the second was to
provide moisture protection. The preservation of the wood against fungus or
termites was generally inconsequential for use as spacers in transmission
lines.
Polyvinyl chloride and chlorinated polyvinyl chloride plastics are
moderately lossy at radio frequencies but are far better than wood in this
respect, and I have seen them used with homebrew transmission lines.
However, from the standpoint of RF losses and ultraviolet radiation damage,
acrylic plastics are my choice as true ladder line insulators.
One suggestion I have is to look at cheap plastic coathangers. These are
about 1/4 inch in diameter and are not vinyl coated wire hangers. Several
insulators can be cut from a single coathanger. Since you can often buy
these hangers for around $1.00 for ten, a few dollars could provide a good
number of insulators. If you don't like the color, spray paint them with
Krylon or another acrylic paint. White will provide the best ultraviolet
resistance. I would limit my wire size to 16 Gauge or smaller as this
plastic is quite brittle.
73, Dr. Barry L. Ornitz WA4VZQ
John Smith
>> ...
> One suggestion I have is to look at cheap plastic coathangers. These are
> about 1/4 inch in diameter and are not vinyl coated wire hangers. Several
> insulators can be cut from a single coathanger. Since you can often buy
> these hangers for around $1.00 for ten, a few dollars could provide a good
> number of insulators. If you don't like the color, spray paint them with
> Krylon or another acrylic paint. White will provide the best ultraviolet
> resistance. I would limit my wire size to 16 Gauge or smaller as this
> plastic is quite brittle.
>
> 73, Dr. Barry L. Ornitz WA4VZQ
Excellent, comprehensive, broad in scope, generally-good-advise, etc.
Thanks for your time,
regards,
JS
Michael Coslo
> One suggestion I have is to look at cheap plastic coathangers. These are
> about 1/4 inch in diameter and are not vinyl coated wire hangers. Several
> insulators can be cut from a single coathanger. Since you can often buy
> these hangers for around $1.00 for ten, a few dollars could provide a good
> number of insulators. If you don't like the color, spray paint them with
> Krylon or another acrylic paint. White will provide the best ultraviolet
> resistance. I would limit my wire size to 16 Gauge or smaller as this
> plastic is quite brittle.
good post, Barry
The suggestion of plastic coat hangers is interesting. I think I might
try home brewing with some pink ones! 8^)
- 73 de Mike N3LI -
Allodoxaphobia
>
> One suggestion I have is to look at cheap plastic coathangers. These are
> about 1/4 inch in diameter and are not vinyl coated wire hangers. Several
> insulators can be cut from a single coathanger. Since you can often buy
> these hangers for around $1.00 for ten, a few dollars could provide a good
> number of insulators. If you don't like the color, spray paint them with
> Krylon or another acrylic paint. White will provide the best ultraviolet
> resistance. I would limit my wire size to 16 Gauge or smaller as this
> plastic is quite brittle.
Another suggestion: "They" make fiberglass driveway-marker rods which
seem to come in either 4' or 6' lengths. The ones I've used are 3/8" in
diameter and usually are painted International Orange and have a
reflective strip at the top. (Maybe more readily available in hardware
stores for "country folks" who need to come home down a gravel road in
the dark, with 2' of freshly fallen snow...)
I've not used these for feedline spacers, but they seem to be another
choice for that application. I've used them for VHF antenna
construction -- for both fixed and portable antennas.
HTH
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
ml
I also acknowledged that using oil was bad , thats why i then stated
that plastic is a way to go
but it can't be poor per say because the original post asked for
comments on wood, so we gave comments on wood
he also asked about plastics he got comments on plastic
also acknowledged was some pro's and cons
only the user and his applications and desires will determine what
is 'best'
In article <je4Vk.850$VC6...@newsfe25.iad>,
NoSPAM
I apologize if I offended you, but your comments were so poorly written that
it was difficult to understand entirely just what you intended to say.
You suggested using the same methods used to preserve telephone poles. I
discussed both the older methods as well as present day methods of wood
preservation. Wood preservatives and sealers, such as creosote,
pentachlorophenol, and chromated copper arsenate are far too toxic to use.
But more importantly, they are also _very_ poor from an electrical
standpoint in the _original_ application, i.e. for use on wood dowels as
ladderline spreaders. I also clearly stated why boiling the wood dowels in
paraffin wax, as done by oldtimers, did a better job electrically than than
creosote. Previous posts I had written already covered the safety aspects
of using hot paraffin, especially its flash point temperature., and the
extreme danger of skin contact with the hot wax.
You then mentioned that _plastic_ is _a_ way to go. You did not mention
which plastic as this is extremely important in the original application.
Polyolefins (polyethylene, polypropylene) are extremely poor in outdoor use;
they can fall apart quickly if exposed to bright sunlight. Polyamides
(nylons) fare a little better but they too are soon damaged by the
ultraviolet in sunlight. They are also damaged by acid rain.
Polyoxymethylene (Delrin) is quite sensitive to halogens in acid rain.
Polycarbonate and acrylonitrile-butadiene-styrene (ABS) plastics have good
ultraviolet resistance only if stabilizers and absorbers are blended in;
they have good chemical resistance to aqueous acids and bases, but they are
quite prone to solvent attack. Polytetrafluorethylene (PTFE, Teflon) and
other fluoropolymers have wonderful electrical properties (superb insulation
resistance, low dielectric constant and loss tangent) as well as high
ultraviolet and chemical resistance, but most are subject to cold flow and
have poor temsile strength. In other posts I discussed acrylic and
polyester plastics that are inexpensive, have good UV resistance and good
electrical properties. I also discussed polyvinyl chloride and chlorinated
polyvinyl chloride plastics. I didn't bother to consider polyimides
(Kapton) as the cost would have been prohibitive. Suggesting "plastic" as
you did without specifying which particular composition is essentially
useless information. I gave my suggestions and the detailed reasons why I
would pick certain plastics. I did not specifically mention cost except
with the suggestion of plastic coathangers, but as an engineer.cost is an
important consideration for virtually all my decisions. It was certainly a
consideration for the original poster --why else would he ask about using
wood?
Of the three methods of protecting wood in this application. as queried by
the original poster, I plainly stated that urethane varnish would be my
choice. I also explained why this would be preferred over shellac and
paraffin wax. I further suggested which specific plastics would perform the
best for the original application of transmission line spreader.
In the future, you should be far more clear in your writing if you really
want people to take your suggestions seriously. You also need to be far
more specific in your suggestions.
Again I apologize if I offended you, but I still stand by my earlier
postings. If it bothers you, you can always filter out my posts. I
certainly do this for a few of the people found here who espouse
pseudoscience and refuse to defend their claims with either mathematics or
experimental evidence.
73, Dr. Barry L. Ornitz WA4VZQ
"ml" <m...@di.net> wrote in message
news:m-6C57E7.15...@news.optonline.net...
>> these hangers for around $1.00 for ten; a few dollars could provide a