"ml" wrote in message
...
In article ,
"Hal Rosser" 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